Retroviral Defense And Mitochondrial Offense

Chromosomal DNA has played host to the long game of viral insertions that repeat and continue as a genetic and epigenetic symbiosis along its phosphate and pentose sugar backbone. But, the bacterial origin of mitochondria and its hosted DNA also promotes its offense. 

Research suggests that retrovirus insertions evolved from a type of transposon called a retrotransposon. The evolutionary time scales of inherited, endogenous retroviruses (ERV) and the appearance of the zinc finger gene that binds its unique sequences occur over same time scales of primate evolution. Additionaly the zinc-finger genes that inactivate transposable elements are commonly located on chromosome 19. The recurrence of independent ERV invasions can be countered by a reservoir of zinc-finger repressors that are continuously generated on copy number variant (CNV) formation hotspots.

One of the more intiguing aspects of prevalent CNV hotspots on chromosome 19 are their proximity to killer immunoglobulin receptor gene's (KIR's) and other critical gene's of the innate immune system.

Frequently occuring DNA breaks can cause genomic instability, which is a hallmark of cancer. These breaks are over represented at G4 DNA quadruplexes within, hominid-specific, SVA retrotransposons and generally occur in tumors with mutations in tumor suppressor genes, such as TP53. Cancer mutational burden is shaped by G4 DNA, replication stress and mitochondrial dysfunction, that in lung adenocarcinoma downlregulates SPATA18, a mitochondrial eating protein (MIEAP) that contributes to mitophagy. 

Genetic variations, in non-coding regions can control the activity of conserved protein-coding genes resulting in the establishment of species-specific transcriptional networks. A chromosome 19 zinc finger, ZNF558 evolved as a suppressor of LINE-1 transposons, but has since been co-opted to singly regulate SPATA18. These variations are evident from a panel of 409 human lymphoblastoid cell lines where the lengths of the ZNF558 variable number tandem repeats (VNTR) negatively correlated with its expression. 

Colon cancer cells with p53 deletion were used to analyze deregulated p53 target genes in HCT116 p53 null cells compared to HCT116-p53 +/+ cells. SPATA18 was the most upregulted gene in the differential expression providing further insight to p53 and mitophagy via SPATA18-MIEAP.

p53 response elements (p53RE) can be shaped by long terminal repeats from endogenous retroviruses, long interspersed nuclear repeats, and ALU repeats in humans and fuzzy tandem repeats in mice. Further, p53 pervasively binds to p53REs derived from retrotransposons or other mobile genetic elements and can suppress transcription of retroelements. The p53- mediated mechanisms conferring protection from retroelements is also conserved through evolution. Certainly, p53 has been shown to have other roles in DNA  context, such as playing an important role in replication restart and replication fork progression. The absence of these p53-dependent processes can lead to further genomic instability. 

The frequency of variable length, long or short nucleotide repeats and their locations within a gene may be key to the repression of DNA sequences that would otherwise cause genomic instability or protein expressions that would eat bacterial mitochondria or destroy its cell host. 

The complexity of variable length insertions is made evident when exhaustively analyzing a simple length 12 sequence for the potential frequency of each of its variable length repeats starting from a minumum variable length of 8.

Then, for TGTGGGCCCACA(12)

All possible internal variable length combinations from and including length 8:

TGTGGGCC(8)|GTGGGCCC(8)|TGTGGGCCC(9)|TGGGCCCA(8)|GTGGGCCCA(9)|TGTGGGCCCA(10|GGGCCCAC(8)|TGGGCCCAC(9)|GTGGGCCCAC(10)|TGTGGGCCCAC(11)|GGCCCACA(8)|GGGCCCACA(9)|TGGGCCCACA(10)|GTGGGCCCACA(11)|TGTGGGCCCACA(12)

For example, reviewing length (8) only:

TGTGGGCC (8) occurs 5 times

GTGGGCCC (8) occurs 8 times

TGGGCCCA (8) occurs 9 times

GGGCCCAC (8) occurs 8 times

GGCCCACA (8) occurs 5 times

Any repeat can be ranked based on its ocurrence within all possible combinations of a given sequence, known as the repeats' iScore rank. This illustrates a potential useful statistical ranking that, subject to biology may describe a repeats inherency to be more or less effective, in increments of the gene sequence. 

Repression of the most active sequences, especially in context of repeats may result in genetic variation. 

Chemo vs. Mecho

Data strongly suggests interaction between plasma membrane and submembrane at the endothelial surface controls the inflammatory response. 

A meta-analysis from six studies of global gene expression profiles of Blood Pressure (BP) and hypertension was performed in 7017 individuals. 34 genes were differentially expressed. Of these, 6 genes were linked including MYADM, which was the only gene, of 34 discovered across diastolic, systolic BP and hypertension. Knockdown of MYADM (19q13), a component of endothelial surface rafts induced an inflammatory phenotype altering barrier function through the increase of the adhesion receptor ICAM-1 (19p13). This is mediated by MYADM activation of ERM actin cytoskeleton proteins. 

Mechanical forces, without a definitive direction e.g., disturbed flow and relatively undirected stretch at branch points and other complex regions cause sustained molecular signaling of pro-inflammatory and proliferative pathways that include mechanical stretch tied to p53. 

ERM proteins also facilitate Sphingosine-1-phosphate (S1P) dependent egress for T-cells to migrate from lymphoid organs. Their directional migration, by blebbing is contained at the T-cell’s leading edge. This fundamentally different mode of migration is characterized by intracellular pressurization. Of the five S1P receptors S1P2 (19p13) is critical in the immune, nervous, metabolic, cardiovascular, musculoskeletal, and renal systems. Results suggest that the ratio between S1P1 and S1P2 (19p13) governs the migratory behavior of different T cell subsets. 

Human NK cells express S1P1 mRNA. Activation with IL-2 increases S1P1, promotes S1P4 (19p13) and S1P5 (19p13) but not S1P2 (19p13) expression. Unlike S1P1, S1P2 (19p13) signals through several different G-alpha subunits, Gi, G12/13, and Gq. S1P5 (19p13) is also expressed in human and mouse NK cells and was required for mobilization to inflamed organs. S1P5-deficient mice had aberrant NK cell homing during steady-state conditions. NK cell trafficking in vivo requires a dedicated sphingosine 1-phosphate receptor. 

Virus-infected mast cells selectively recruit NK cells and positively modulate their functions through mechanisms dependent on soluble mediators, such as interferons. Skin mast cells protect mice against vaccinia virus by triggering mast cell receptor S1P2 (19p13) and releasing antimicrobial peptides. S1P2 (19p13),  a negative regulator of platelet derived growth factor (PDGF) induced migration and proliferation as well as SphK1 expression. 

S1P inhibits macropinocytosis (internalizing extracellular materials) and phosphorylation of Akt via S1P2 (19p13) stimulation resulting in diminished antigen capture.

S1P1, S1P2 (19p13) and S1P3 receptors have redundant or cooperative functions for the development of a stable and mature vascular system during embryonic development. S1P2 (19p13)  and S1P3 are involved in regulation of endothelial barrier function, fibrosis, and vasoconstriction. 

Adipogenic differentiation is inhibited by S1P2 (19p13) as mediated by C/EBPα and PPARγ, which induces PEPCK, a more recent gene of interest in cancer that acts at the junction between glycolysis and the Krebs cycle.

Mecho or chemo, chicken or egg, what first?

Blood Pressure, Immunity and p53 Checkpoint.

Background

A few chromosome 19 curiosities developed into a deep-dive after looking into the primordial immune complex, the origins of MHC Class I and antigen receptors as revealed by comparative genomics. And the plot thickened because repressors (of endogenous retroviruses) that gained their binding affinity to retrovirus sequences at the same time their targets invaded the human lineage are preferentially located on chromosome 19. Further, the deletion rate in Zinc Finger clusters (ZNF) located around 19p.12 and 19q13.42, particularly between 51,012,739 and 55,620,741 are about twofold higher than the background deletion rate. A lot going on at this very active location which motivated this article.

At 19q13.42 kallikrein related peptidase (KLK’s), leukocyte immunoglobulin-like receptors (LILR’s) including killer-cell immunoglobulin-like receptor (KIR’s) as well MYADM, an important blood pressure related gene may also provide some clues to immunity variables that originate from or are influenced by this volatile region.

The retrotransposon bombardment of 19q13.42 and double background deletion rate is a significant remnant. However, after evolutionary MHC changed chromosomes ZNF, and within its range the chromosome 19 miRNA cluster (C19MC - 53,671,968 and 54,264,387) were still subjected to the deleterious effect of transposons. Regardless, suppression mechanics have kept epigenetic, regulatory and transcription processes, across gene’s far and wide on the move at a relatively stable rates. For example, reverse-transcribed SARS-CoV-2 RNA can integrate into the genome of cultured human cells and can be expressed in patient-derived tissues, but the effects of suppression may be sufficient to illicit a more permanent natural defense. In any event insertions and DNA damage are closely related and associated with loss of p53 that results in centrosome amplification. 

As cells pass through epithelial to mesenchymal transition (EMT), DNA damage prevents the normal reduction of p53 levels diverting the transcriptional program toward mesoderm without induction of an apoptotic response. In contrast, TP53-deficient cells differentiate to endoderm with high efficiency after DNA damage, suggesting that p53 enforces a “differentiation checkpoint” in early endoderm differentiation that alters cell fate in response to DNA damage.

Reproduction, Blood Pressure and NK

In reproduction, some of the 59 known miRNAs from primate-specific C19MC are highly expressed in human placentas and in the serum of pregnant women. They are also packaged into extracellular vesicles of diverse sizes, including exosomes and endow non-trophoblast cells with resistance to a variety of viruses. At least miR-517a-3p (a C19MC from fetal placenta) was incorporated into maternal NK cells in the third trimester, and it was rapidly cleared after delivery. miRNA's regulate the migration of human trophoblasts and suppress EMT genes critical for maintaining the epithelial cytotrophoblasts stem cell phenotype. 

Maternal uterine or decidual Natural Killer cells (dNK) express AT1, AT2, ANP, proteins of Renin Angiotensin System (RAS) suggesting dNK have the potential to contribute to changes in blood pressure that occur between days 5 and 12 of pregnancy in mice. And, pressure related mechanical stretch on endothelial cells interconnects innate and adaptive immune response in hypertension.

Pressure variables in cells and tissues may result from infection, inflammation and membrane stretch, including inner mitochondrial membrane that affects electron transport chain, endoplasmic reticulum, antigen production, presentation and exosome bound p53 / miRNA release.  ANP colocalization to dNK’s suggests that dNK RAS, at day 12 infers a localized RAS related responsiveness. STAT3 in monocytes was activated by increased endothelial stretch and is involved in driving almost all of the pathways that control NK cytolytic activity as well as the reciprocal regulatory interactions between NK cells and other components of the immune system. The crosstalk between STAT3 and p53/RAS signaling controls cancer cell metastasis and cisplatin resistance via the Slug/MAPK/PI3K/AKT-mediated regulation of EMT and autophagy.

Educating NK Subsets 

Looking into some of the ~15 genes scattered among C19MC (~sixty miRNA's) between 53,671,968 and 54,264,387;

1. MYADM was one of two blood pressure signature genes (copper uptake protein the other) differentially expressed for systolic, diastolic blood pressure and hypertension. Of the ~35 identified genes, several more strongly related to immune cell functions including PRF1, GNLY, TAGAP, IL2RB, GZMB and CD97, NKG7, CLC that are located on chromosome 19. The endothelium maintains a barrier between blood and tissue that becomes more permeable during inflammation. MYADM controls endothelial barrier function through ezrin, radixin, and moesin dependent regulation of ICAM-1 expression an essential receptor for NK interaction.

2. PRPF31 is recruited to introns following the attachment of U4 and U6 (spliceosome) RNA’s. Experiments using PRPF31 determined p53 activation is a general consequence of interfering with the spliceosome. 

3. At 54,617,158 LILRB1 receptor is expressed on immune cells where it binds to MHC class I molecules on antigen-presenting cells and transduces a negative signal that inhibits stimulation of an immune response. LILRB1 has a polymorphic regulatory region that enhances transcription in NK Cells and recruits zinc finger protein YY1 that inhibits p53. It also educates expanded human NK cells and defines a unique antitumor NK cell subset with potent antibody-dependent cellular cytotoxicity.

Monocyte/macrophage immunoglobulin-like receptors (MIR) genes are closely linked to the KIR gene family and the gene for FcαR at 19q13.4. The linkage was discovered in 1997 when a mouse sequence related to MIR mapped to a region on chromosome 7 syntenic with human 19q13.4. In 2012 a cluster of genetic loci, from multiple mouse strains and across anatomical sites was found to jointly contribute to the development of both thymic and splenic invariant natural killer T-cell NKT-cell levels. The dominant cluster was on mouse chromosome 7 and included almost all the non-C19MC genes located within the human C19MC region:– MYADM, CACNG7, VSTM1, TARM1, PRKCC(G), TFPT, NDUFA3, CNOT3, LENG1, TSEN34, RPS9. 

Four of nineteen knockout genes, that enhanced NK cell function were on chromosome 19 including GSK3 that phosphorylates Mdm2 to regulate p53 abundance, which would contribute to NK enhancement. 

A study of MHC disassortative mating in humans found Israeli’s were more gene similar, but MHC dissimilar than Europeans who were gene dissimilar and MHC dissimilar . Now, a recent study in American Indians found remarkably low KIR and HLA diversity in Amerindians that revealed signatures of strong purifying selection shaping the centromeric KIR region. This narrows to the importance of LILR-KIR region on chromosome19 that codes for the strongest NK cell educator receptors.

p53 regulates exosomes and miRNA’s directly influence NK responsiveness including regulation of dNK during pregnancy. Exosomes regulated by p53 also transfer it and can suppress growth and proliferation of p53 negative cells. Further, miRNA’s, induced by p53 can directly target ULBP2 mRNA and reduce its cell-surface expression.

Disease highlights

 

rs78378222 polymorphism in the 3'-untranslated region of TP53 contributes to development of age-associated cataracts by modifying miRNA-125b-induced apoptosis of lens epithelial cells. miRNA-125b is a novel negative regulator of p53. Deleting PRPF31 activates the p53 pathway and triggers retinal progenitor cells apoptosis. The members of the miR-125 family (miR-125a on chromosome 19q13.4 and miR-125b on chromosome 21q21.1) reside in two distinct human miRNA clusters with the let-7 and miR-99 families and these miRNAs are thus likely co-transcribed.

  

More succinctly, NK cells are alerted to induction of p53 in cancer cells by upregulation of the NKG2D ligands ULBP1 and ULBP2. p53 also induces expression of miR-34a and miR-34c, which target ULBP2 mRNA for destabilization. Observations suggest two possibly contrasting roles for p53 in NKG2DL expression and requires more investigation into how the regulation is fine-tuned. Extending this model to human populations would suggest that p53 must be inactivated among those with a robust NK response (those with B haplotypes). 

Taken together, our data suggest functional interactions between KIR and HLA modify risks of basal cell carcinoma (BCC) and squamous cell carcinoma, and that KIR encoded by the B genes provide selective pressure for altered p53 in BCC tumors. 

Conclusion

The convergence of several important cellular mechanisms that point back to a 19q13.42 address may illustrate ancient and conserved elements that perpetuate and function as integrated biological units effecting blood pressure, reproduction and immunity. Many of these impart education to innate immunity.

Life, Dormancy or Death?

Cellular biology is viewed through different lenses, but pregnancy offers a perspective on the invasive origin of cell division, the senescent state and cancer. Pregnancy causes Natural Killer cells of the decidua (dNK) to expand abundantly until they represent as much as 30% of the mucous membranes' cells. NK cells may be induced to expand by invading trophoblasts to realize the dNK trifecta - robust innate immunity that protects the embryo from maternal infection, modulation of trophoblast invasion and driver of vascular remodeling. However, in many cancers expansion of diverse NK populations fails to materialize and missing sub-sets of NK cell diversity provides a path for cancers unchecked growth. 

In decidual cells at the human maternal-fetal interface, CD82 - the metastasis suppressor may participate in intercellular communication with trophoblasts and limit their invasiveness. Trophoblasts enhance adhesiveness of dNK to the decidua's stromal cells, via the CXCL12/CD82/CD29 signaling pathway which contributes to CD56bright NK cell enrichment a necessary element for heathy pregnancy.

CD82 expression is downregulated in tumor progression of many human cancers and strongly correlated with tumor suppressor p53. It can be activated by p53 through a consensus binding sequence in the promoter. In human ovarian cancer a sequential genetic change at the TP53 and the CXCL12 receptors CXCR4  locus occurs during transformation of surface epithelium. Basal CXCR4 promoter activity in HCT116 colon carcinoma cells deleted of p53 was10-fold higher compared to that in parental HCT116 cells with functional wild-type p53.

The CXCL12 ligand is unique for its CXCR4 receptor and both are expressed in human first-trimester endometrial epithelial cells (EECs) at the mRNA and protein level. EEC-conditioned medium and recombinant human CXCL12 significantly increased the migration and invasion of EECs. CXCL12 has also been associated with the recruitment of CD56bright CD25+ dNK subsets in early pregnancy's.

CXCR4 is specifically upregulated in the human endometrium during the implantation window and increased immunostaining observed only when a blastocyst is present. CXCR4/CXCL12 not only enhances trophoblast invasiveness, but also limits over-invasiveness by upregulating CD82. CXCR4 activation increases the CXCL12-CXCR4 signaling axis stimulates vascular endothelial growth factor (VEGF) synthesis which induces CXCR4 and CXCL12 production. This synergistic regulation influences placental vascularization. CXCR4 suppresses apoptosis and increases the viability of trophoblasts. 

Undetectable disseminated tumor cells, in different tissue microenvironments restrain or allow the progression of breast cancer in the liver where in dormant milieu's there are selective increases in NK cells. Stroma crosstalk and exit from dormancy follows a marked contraction of the NK cell compartment and concurrent accumulation of activated hepatic stellate cells (aHSCs). Proteomics on liver co-cultures implicate aHSC-secreted CXCL12 in the induction of NK cell quiescence through CXCR4. CXCL12 expression and aHSC abundance are closely correlated in patients with liver metastases and were inversely correlated with NK cell abundance.

The dNK behavior that checks trophoblast invasion and promotes vascularization resembles immediate and invasive new cancers that may occur in cells of any tissue environment. Similarly expansion of resident tissue NK sub-sets in response may be the determiner of life, the shape of next generation cells, dormancy or death.  

Immunity keeping p53 in check!

In a 2012 study on the topology of the human and mouse m6A RNA methylomes, Gene Ontology (GO) analysis of differentially expressed genes (DEG's) indicated a noteworthy enrichment of the p53 signaling pathway: 22/23 genes had differentially expressed splice variants, of which 18 were methylated. Moreover, 15 other members of the signaling pathway, which were not significant DEG's, exhibited significant differential isoform expressions. For example, isoforms of MDM4, needed for p53 inactivation were downregulated. Similar pro-apoptotic effects were observed in other pathway genes including MDM2, FAS and BAX. Higher apoptosis rate in HaCaT-T cells resulted with knockdown of m6A subunit METTL3, which also reversed a significant decrease in p53 activity. Modulation of p53 signaling through splicing may be relevant to induction of apoptosis by silencing of METTL3. 

Then, in 2019 a study of arsenite-induced human keratinocyte transformation demonstrated that knockdown of METTL3 significantly decreased m6A level, restored p53 activation and inhibited cellular transformation phenotypes in the-transformed cells. Further, m6A downregulated the expression of the positive p53 regulator, PRDM2, through the YTHDF2-promoted decay of PRDM2 mRNAs. m6A also upregulated expression of negative p53 regulator, YY1 and MDM2 through YTHDF1-stimulated translation of YY1 and MDM2 mRNA. Taken together, the study revealed the novel role of m6A in mediating human keratinocyte transformation by suppressing p53 activation and sheds light on the mechanisms of arsenic carcinogenesis via RNA epigenetics.

Finally in 2021 a discovery that YTHDF2 is upregulated in NK cells upon activation by cytokines, tumors, and cytomegalovirus infection. Ythdf2 deficiency in NK cells impaired its anti-tumor and anti-viral activity in vivo. YTHDF2 maintains NK cell homeostasis and terminal maturation, correlating with modulating NK cell trafficking and regulating Eomes, respectively. It promotes NK cell effector function and is required for IL-15-mediated NK cell survival and proliferation by forming a STAT5-YTHDF2 positive feedback loop. Analysis showed significant enrichment in cell cycle, division, and division-related processes, including mitotic cytokinesis, chromosome segregation, spindle, nucleosome, midbody, and chromosome. This data supports roles of YTHDF2 in regulating NK proliferation, survival, and effector functions. Transcriptome-wide screening identified Tardbp (TDP-43) to be involved in cell proliferation or survival as a YTHDF2-binding target in NK cells.

Downregulation of METTL3, which in spinal cord contributes with YTHDF2 to modulate inflammatory pain may upregulate differentially expressed p53 network splice variants that oppose YTHDF2 induced downregulation of p53, via PRDM2 leading to apoptotic or diseased cells. In diseased environments cytokines may upregulate YTHDF2 in NK cells leading to downregulation of p53 and cytoskeletal transformation that may be sufficient, at an immune synapse to advance cytolysis.

p53 signals may inform selections of cells and tissue that prime NK cells for advanced, personalized immune therapy. 

First Intron DNA - Site for a Genetic Brain?

DNA Methylation

The first intron of a gene, regardless of tissue or species is conserved as a site of downstream methylation with an inverse relationship to transcription and gene expression. Therefore, it is an informative gene feature regarding the relationship between DNA methylation and gene expression. But, expression in induced pluripotent stem cells (iPSC's) has been a major challenge to the stem cell industry, because by comparison these cells have not yet reached the state of natural pluripotent or embryonic stem cells (ESC's).

In mice two X chromosomes (XC) are active in the epiblasts of blastocysts as well as in pluripotent stem cells. One XC is inactivated triggered by Xist (non coding) RNA transcripts coating it to become silent. Designer transcription factor (dTF) repressors, binding the Xist intron 1 enhancer region caused higher H3K9me3 methylation and led to XC's opening and X-linked gene repression in MEFs. This substantially improved iPSC production and somatic cell nuclear transfer (SCNT) preimplantation embryonic development. This also correlated with much fewer abnormally expressed genes frequently associated with SCNT, even though it did not affect Xist expression. In stark contrast, the dTF activator targeting the same enhancer region drastically decreased both iPSC generation and SCNT efficiencies and induced ESC differentiation. 

A genome-wide, tissue-independent quasi-linear, inverse relationship exists between DNA methylation of the first intron and gene expression. More tissue-specific, differentially methylated regions exist in the first intron than in any other gene feature. These have positive or negative correlation with gene expression, indicative of distinct mechanisms of tissue-specific regulation. CpGs in transcription factor binding motifs are enriched in the first intron and methylation tends to increase with distance from the first exon–first intron boundary, with a concomitant decrease in gene expression.

Since the relationship between sequence, methylation, repression and transcription is determinative in ESC differentiation it may also suggest a broader link to differential translation. Translation is required for miRNA-dependent transcript destabilization that alters levels of coding and noncoding transcripts. But, steady-state abundance and decay rates of cytosolic long non-coding RNA's (lncRNAs) are insensitive to miRNA loss. Instead lncRNAs fused to protein-coding reporter sequences become susceptible to miRNA-mediated decay. 

In this model, first intron DNA sequences that are differentially methylated, bind transcription factors that effect transcription, impact splicing, expressions of coding or non-coding transcripts and transcript destabilizations resulting in differential rates and possible variations in translation. This bottom-up, dynamic view of the classical process may elevate the first intron from 'junk' to a DNA 'brain' because it plays a more extensive role, heading the process toward translation of any gene or switching it off entirely.  

For this reason, among others Codondex uses first intron k-mers relative to the transcripts mRNA as the basis for comparing same gene transcripts in diseased cells or tissue samples. Further, p53 and BRCA1 miRNA key sequences, discovered using Codondex iScore algorithm, when transfected into HeLa cells resulted in significantly reduced proliferation that may result from this accelerated, transfected miRNA dependent decay.

 

Short Sequences of Proximally Disordered DNA

Oxford Nanopore Device Reducing Sequencing Cost

Relationships exist between short sequences of proximal DNA (SSPD) of a gene that when transcribed into RNA present stronger or weaker binding attractions to RNA binding proteins (RBP'S) that settle, edit, splice and resolve messenger RNA (mRNA). Responsive to epigenetic stimuli on Histones and DNA, mRNA are constantly transcribed in different quantity, at different times such that different mRNA strands are transported from the nucleus to cytoplasm where they are translated into and produce any of more than 30,000 different proteins.

Single nucleotide polymorphisms and DNA mutations can alter SSPD combinations in different diseased cells thus altering sequence proximity, ordering that affects transcribed RNA's attraction and optimal binding of RBP's. This may result in modified splicing of RNA, assembly of mRNA and slight or major variations in some or all translated protein derived from that gene. 

The specific effects of these DNA variations, on the multitude of proteins produced are generally unknown. However, it remains important to understand their effects in disease, diagnosis and therapy. Typically these have historically been researched by large scale analysis of RBP on RNA as opposed to the more fundamental, yet underrepresented massive array of diseased variant DNA to mRNA transitions.

Most pharmaceutical research is directed to a molecular interference targeting an aberrant protein to cure widely represented or highly impactful disease conditions of society. Economic assessments generally influence government decisions to support research based on loss of GDP contribution by a specific disease in a  patient cohort. However, in the modern multi-omics era top down research into protein-RNA activity is descending deeper into the cell to include RNA-mRNA and mRNA-DNA customizable therapies that will eventually resolve individually assessed diseases at a price that addresses much larger array of patient needs.  

SNP's and other mutations can vary considerably in cells. These variations can cause instability during division and lead to translated differences that can ultimately drive cancerous cell growth to escape patient immunity. Like a 'whack-a-mole' game, pattern variation and mechanistic persistence eventually beat the player. Without effective immune clearance these cells can replicate into tumors and contribute to microenvironments that support their existence.

Link to video on tumor microenvironment https://youtu.be/Z9H2utcnBic

We thought to analyze DNA and mRNA transcripts from cells in tumors and their microenvironments to see if we could expose the SSPD disordered combinations that may have promoted sub-optimal RBP attractions and led to sustained immune escape. Given the complexity of DNA to mRNA transcription, for any given gene many distortions in gene data sets have to be filtered. To do that we focused on p53, the most mutated gene in cancer. We designed a method to compare sequences arrays of DNA and mRNA Ensembl transcripts, from the consensus of healthy patients to multiple cell samples extracted from different sections of a patients tumor and tumor microenvironment.     

We previously identified and measured different levels of Natural Killer (NK) cell cytotoxicity, produced from cocultures with the extracted samples of each of the multiple sites of a biopsy. We will measure the different p53 transcript SSPD combinations associated with each sample and determine whether disordered SSPD's corelate with NK cytotoxicity from each coculture. We expect to identify whether biopsied tumor cells, ranked by SSPD's predict the cytotoxicity resulting from NK cell cocultures. We will narrow our research to identify the varied expressions of receptor combinations associated with degrees of cytotoxicity. We will test immune efficacy to lyse and destroy tumor cells. Finally we will test for adaptive immune response. 

Our vision is for per-patient, predictable cell co-culture pairings, for innate immune cell education based on ranking DNA-mRNA combinations to lead to multiple effective therapies. The falling cost of sequencing and sophistication of GMP laboratories presently servicing oncologists may support a successful use of this analytical approach to laboratory assisted disease management.

   

 

Non-Coding DNA Key Sequences

DNA Structural Inherency

Wind two strands of elastic, eventually it will knot, ultimately it will double up on itself. Separate the strands. From the point of unwinding, forces will be directed to different regions and the separation will approximately return to the wound state of the band. Do the same with each of 10 different bands or strings of any type, they will all behave in much the same way. For a given section of DNA being transcribed, the effect of separation will be much the same. For a given gene, there will be sequences that can tolerate force to greater or lesser degrees. For different transcripts, of a gene variation at those sequences may be crucial to the integrity of transcription machinery that separates DNA strands to initiate replication to RNA and for the outcome.

Cellular biology is enormously complex in all regards. The physics of molecular interaction, fluid dynamics, and chemistry combine in a system where cause and effect is near impossible to predict. At the most elementary level we hypothesize some non-coding DNA (ncDNA) possess structural inherencies that can be deployed to direct gene proteins and cell function for diagnosis or therapy.

Coding DNA and its regulatory, non-coding gene compliment is transcribed and spliced from a transcribed gene. Transcription to RNA, edited mRNA, spliced non-coding RNA and ultimately mRNA translation to protein can produce wide ranging, variable outcomes that may not be re-captured experimentally. 

A single nucleotide polymorphism (SNP) or SNP combinations within a gene may affect the finely tuned balance that results. Under different environmental conditions this could be material to the protein produced. Additionally other mutations of the gene could add complexity to the environment and/or the  resulting protein translation. 

At this level of cellular biology, genetic DNA stores instruction for protein assemblies to produce new protein required for the fully functional cell. However, DNA's stored mutations can lead to different functional or non-functional versions of protein depending on many different factors. Relationships between ncDNA, including mutations and the transcripts' edited, protein coding mRNA may represent unexplored inherencies that can regulate the gene's mRNA or translated protein.

We built an algorithm to elaborately compare ncDNA sequences of multiple protein coding transcripts of the same gene. For each transcript it steps through every variable length ncDNA sequence (kmer) (specifically intron1), computes a signature for each and indexes it to the constant of the transcripts' mRNA signature. For each step these signatures order the kmers for each of the transcript's. The order is represented in a vector of all the transcripts being compared.  

At millions of successive steps (depending on total intron 1 length's) transcripts mostly retain their vector ordering except, as expected at a kmer length change. Mostly transcript order in the vector does not change, occasionally a few positions change, vary rarely do all positions change. Position changes that cause another, like a domino effect are filtered out. For the rarest positions changes at a step, we look to the root causes in the kmer (sequence). We call this a Key Sequence because it is identified by the significance of changes to transcript positions in the vector compared to the vector at the next step. 

Therefore, Key Sequences cause the most position changes between transcripts being compared by the algorithm. This relative measure is step dependent and Key Sequences are discovered by comparing transcript positions in the vector at the next step location. Logically, this infers a genes structural inherency discovered through ncDNA Key Sequence relationships to mRNA, to other transcripts, error in gene alignments, sequenced reads or the algorithm. 

In assay testing we were able to predict and synthesize non-coding RNA Key Sequences that significantly reduced proliferation of HeLa cells. In our pre-clinical work, based on comparisons to transcripts of the TP53 we will be predicting the efficacy of cell and tissue selections that educate and activate Natural Killer cells.

If Key Sequences are inherent they could open a new frontier for diagnosis and therapy.

IFN-γ Concentration, p53 and Immune Sensitivity

IFN-γ 

Dimorphic complexity between Human Leukocyte Antigen (HLA) and Killer Immune Receptor (KIR) haplotypes introduce significant challenges for personalized Natural Killer (NK) and immune cell therapy. In vitro models support a p53 requirement for upregulation of NK ligands and there is a strong association between the KIR B haplotype and p53 alteration in Basal Cell Carcinoma's (BCC) with a higher likelihood that KIR B carriers harbor abnormal p53. Data suggests that KIR encoded by B genes provides selective pressure for altered p53 in, at least BCC's. 

Breast cancer (BC) patients exhibit reduced NK-cytotoxicity in peripheral blood. To test whether certain KIR-HLA combinations impair NK-cytotoxicity that predispose to BC risk, KIR and HLA polymorphisms were analyzed in 162 women with BC and 278 controls. KIR-B genotypes increased significantly in BC. Certain activating KIR (aKIR) HLA ligand combinations were significantly increased in advanced-BC patients whose combinations also shared specific inhibitory KIR (iKIR) counterparts. Contrarily, iKIR-HLA pairs without their aKIR-HLA counterparts were significantly higher in controls. The data suggests NK cells expressing iKIR to cognate HLA-ligands in the absence of specific aKIR counterpart are instrumental in antitumor response. 

The TP53 family consists of three sets of transcription factor genes, TP53, TP63 and TP73, each expresses multiple RNA variants and protein isoforms. TP53 is mutated in 25-30% of BC's, but the effect of isoforms in BC is unknown. Predicted changes in expression of a subset of RNAs involved in IFN-γ signaling were confirmed in vitro. Data showed that different members of the TP53 family can drive transcription of genes involved in IFN-γ signaling in different BC subgroups. Moreover, tumors with low IFN-γ signaling were associated with significantly poorer patient outcome.

NK receptor NKG2D interacts with several virus or stress inducible ligands, including ULBP1 (NKG2DL1) and -2 expressed on target cells. Induction of wild-type p53, but not mutant p53, strongly upregulated mRNA and surface expression of ULBP1 and -2, but not other ligands. An intronic p53-responsive element was discovered in these genes. Coculture of wild-type, p53-induced human tumor cells with primary human NK cells enhanced NKG2D dependent degranulation and IFN-γ production by NK cells.  

In the Tumor Micro Environment (TME) IFN-γ is produced at various concentrations in response to numerous immune stimulants and highlights the need for more personalized, disease centric approach. Engagement of IFN-γ Receptor on distinct tumor stromal cells, induction of interferon stimulated genes, immune status of the TME, and IFN-γ concentration are recognized as critical determinants for IFN-γ-mediated outcomes. Notably, an appropriate antitumor concentration of IFN-γ has yet to be determined. Interestingly IFN-γ produced by NK cells is said to be an essential mediator of Angiotensin II inflammation and vascular dysfunction.

Pharmacological activation of p53 exerts a potent antileukemia effect on antitumor immunity, including NK cell-mediated cytotoxicity against acute myeloid leukemia (AML). Interestingly, orally administered DS-5272 (a potent inhibitor of MDM2 - promotor of p53 degradation) induced upregulation of CD107a and IFN-γ in NK cells but not in CD8+ T cells. Furthermore, coculture of NK cells with leukemia cells resulted in massive apoptosis. 

Findings strongly suggest an interaction between B7 (NK receptor) molecules contribute to a particular design of the inflammatory microenvironment including B7-H6 and PD-L1, for which therapy was enhanced by expanded NK autologous or donor cells. RNA transfections, into HeLa cells of p53 or BRCA1 intron1 Key Sequences (based on Codondex iScore's most significant mRNA-intron1 variations) caused several genes to be upregulated, +1500% above control including B7-H6 (NCR3LG1) ligand for NCR3 (Nkp30) NK cell receptor which, when engaged triggers IFN-γ release. NCR3 and soluble isoforms of Leukocyte Specific Transcript 1 may play a role in inflammatory and infectious diseases. 

Blockade of B7-H3 prolonged the survival of SKOV3 ovarian cancer cell, an in ovarian tumor-bearing mice, miR-29c improved the anti-tumor efficacy of NK-cell by directly targeting B7-H3. miR-29c downregulates B7-H3 and inhibits NK-cell exhaustion. Low levels of mir-29c have been associated with mutated p53 in BC patients. miR-29 miRNAs activate p53 by targeting p85α and CDC42 and upregulate p53 levels that induce apoptosis in a p53-dependent manner. miR-29 controls innate and adaptive immune responses to intracellular bacterial infection by targeting IFN-γ. 

Besides (intron predominant) human ALU repeats, reverse complementary sequences between introns bracketing circRNAs are highly enriched in RNA editing or hyper-editing events. Knockdown of double stranded RNA-editing enzyme - ADAR1 significantly and specifically upregulated circRNA expression. In its absence (interferon stimulating) oligoadenylate synthetase (OAS) can be activated by self-dsRNA (in contrast to viral dsRNA), resulting in RNase L activity and cell death. Conversely, OASL1 expression enhanced RIG-I-mediated IFN induction. In cells absent of p53, immunogenic, endogenous mitochondrial dsRNA are produced and processed by the OAS/RNase L system presenting a novel mechanism in diseases with aberrant immune responses. IFN-γ restores the impaired function of RNase L and induces mitochondria-mediated apoptosis in lung cancer. The p53—OAS axis, in mitochondrial RNA processing may prevent self-nucleic acid such as dsRNA from aberrantly activating innate immune responses.

A plethora of evidence supports bottom up approach to personalized therapy. A p53 intron1-mRNA regulatory loop, as a potential mechanism in IFN responses to infection and disease may be diagnostic. Pre-clinical research, presently underway will establish whether p53 is diagnostic for specific selections of a biopsy to educate NK cells and trigger effective immune response.

Custom Immunotherapy To Address Dimorphic Complexities.

Dimorphic relationships between genes on Chromosome (Chr)6, encoding Human Leukocyte Antigens (HLA) and those on Chr19, encoding Killer-cell immunoglobulin-like receptors (KIRs) may eventually uncover important information as to how, why and when Natural Killer (NK) cells determine self restraint or attack cells infected by pathogens and disease. These proteins emerge from their respective zones, on each chromosome that have and continue to be subject to frequent recombination events.

The active region of Chr19 has a long history of recombinations that have and continue to define the expression patterns of telomeric and centromeric proportions of KIR gene's encoding receptors that bind cells presenting MHC class 1, HLA haplotype combinations that vary significantly across tissues in different population groups. Adding complexity, HLA genes on Chr6 are also subject to significant recombination making the dimorphic functional HLA-KIR interactions difficult to predict. 

Studies across population groups reveal the great diversity of HLA-KIR dimorphisms. The Southern Han centromeric KIR region encodes strong, conserved, inhibitory HLA-C-specific receptors, and the telomeric region provides a high number and diversity of inhibitory HLA-A and -B-specific receptors. In all these characteristics, the Chinese Southern Han represent other East Asians, whose NK cell repertoires are thus enhanced in quantity, diversity, and effector strength, likely augmenting resistance to endemic viral infections.

One study goes much further suggesting that functional interactions between KIR and HLA modify risks of basal cell carcinoma (BCC) and squamous cell carcinomas (SCC) and that KIR B haplotypes provide selective pressure for altered p53 in BCC tumors. This preference implicates multi-modal p53 mechanisms that are also known to upregulate NK ligands, induce HLA-A11 assembly against Epstein Bar Virus and bind a frequently mutated p53 peptide in a complex with HLA-A and presented at the cell surface that prevent T-Cell response. In support, selected p53 mutations altering protein stability can modulate p53 presentation to T cells, leading to a differential immune reactivity inversely correlated with measured p53 protein levels.

In addition to KIR, adaptive NKG2C+ NK cells display fine peptide specificity selectively to recognize HCMV strains that differed by a single substitution in the HLA-E-binding UL40-derived peptide during infection. Distinct peptides controlled the degree of proliferation in synergy with pro-inflammatory cytokines. Viral peptides are known to augment inhibition at NKG2A. Conversely, NKG2A+ NK cells sense MHC class I downregulation more efficiently than KIRs. Thus, both receptor:ligand systems appear to have complementary functions in recognizing changes in MHC class I.

Polymorphic landscapes across HLA, KIR and NKG receptor repertoires coupled with receptor:ligand haplotype cross referencing makes it near impossible to predict therapeutic targets across the breadth of disease and disease combinations that affect populations. A recent KIR-HLA co-existence study of haplotypes in Breast Cancer patients and controls highlights this complexity. 

Genetic signatures that target discovery of desired cell functionality to select preferential cells/tissues from micro environments used to educate and license autologous or allogeneic NK cells may tease specific, finely tuned, intact receptor repertoires. Once licensing efficacy is reached, expanding NK cell populations and applying them to act upon previously unrecognizable cells of a patient becomes the next frontier of immune therapy. This is the exciting work presently being undertaken by researchers and staff working with Precision Autology using Codondex methodologies. 

Cell's with an Index like Google?

Its been a while since I last wrote about DNA repeats or their RNA descendants. In that time advanced research has emerged relating repeats to increasing numbers of viral or other disease. Generally the repeats of interest here can be either long or short sequences of nucleotides that from part of an unspliced gene. Logically, counts of long sequences that repeat would be less than short sequences, but when normalized to their respective nucleotide lengths the indexed results can shift the relative order of repeating sequences quite dramatically.

In most knowledge systems repeats in low level data present redundancy and opportunity to improve efficacy in local or global upstream processes acting on that data. We see this in the structure of efficient alphabets that had a significant impact on whether or not a language survived continuous use. Why use ten words when precise meaning, including abstracts can be derived from three. Or why alpha when, at least for some period in the language history alphanumeric made it more effective? 

Search engines reduce their primary index to the least redundant data set used to drive efficient data access by upstream requests and processes to satisfy any query. However, at the storage level, data redundancy is permitted because energy efficiency is gained. Similarly genetic DNA is massively redundant. Redundant data stores can make highly indexed systems more efficient because frequently accessed data elements are more accessible at multiple locations and parallel processes can more efficiently satisfy upstream requests.

Repetitive sequences constitute 50%–70% of the human genome. Some of these can transpose positions, these transposable elements (TE's) are DNA transposons and retrotransposons. The latter are predominant in most mammals and can be further divided into long terminal repeat (LTR)-containing endogenous retrovirus transposons and non-LTR transposons including short interspersed nuclear elements (SINEs) and long interspersed nuclear elements (LINEs). The most abundant subclass of SINEs comprises primate-specific Alu elements in human with more abundant GC-rich DNA. Humans have up to 1.4 million copies of these repeats, which constitute about 10.6% of the genomic DNA. Long interspersed element-1 (LINE1 or L1), are abundant in AT-rich DNA, constitute 19% of the human genome and make up the largest proportion of transposable element-derived sequences.

Most TE classes are primarily involved in reduced gene expression, but Alu elements are associated with up regulated gene expression. Intronic Alu elements are capable of generating alternative splice variants in protein-coding genes that illustrate how Alu elements can alter protein function or gene expression levels. Non-coding regions were found to have a great density of TEs within regulatory sequences, most notably in repressors. TEs have a global impact on gene regulation that indicates a significant association between repetitive elements and gene regulation.

In liquid systems, phase separation is one of the most fundamental phase transition phenomena and ubiquitous in nature. De-mixing of oil and water in salad dressing is a typical example. The discovery of biological phase separation in living cells led to the identification that phase-separation dynamics are controlled by mechanical relaxation of the network-forming dense phase, where the limiting process is permeation flow of the solvent for colloidal suspensions and heat transport for pure fluids. The application of this derived governing universal law is a step to understanding and defining the liquid biological indexing equivalence of data-processing systems and inherent genetic redundancy.

Repeats have been widely implicated. In plant immunity a TE has been domesticated through histone marks and generation of alternative mRNA isoforms that were both directly linked to immune response to a particular pathogen. p53 transcription sites evolved through epigenetic methylation, deamination and histone regulation that constituted a universal mechanism found to generate various transcription-factor binding sites in short TE's or Alu repeats. In disease cytoplasmic synthesis of Alu cDNA was implicated in age related macular degeneration and there is transient increase of nearly 20-fold in the levels of Alu RNA during stress, viral infection and cancer.

In chromosomal DNA, each sequence, relative to its length may conveniently describe a phase-separated indexed location and method for discovery. Repeats within genetic DNA may present precisely sensitive phase-separated guidance to drive histone, epigenetic and transcription factors to specific genetic locations at the cells' 'end-of-line' from where the genetic response to upstream membrane bound changes begin.

 

Systolic Blood Pressure and Innate Immunity vs. the Cancer Brain

Participants with a valid heart disease phenotype (atherosclerosis) were identified in a MESA blood pressure analysis conducted over 10 years. The valid group varied from 770 to 1113 patients from whom further blood analysis queried a primary and exploratory hypothesis of immune cell subsets. Four statistically significant innate cell subsets were discovered to be associated with Systolic blood pressure (SBP); Natural Killer (NK) cells, gamma delta T cells and classical monocytes.

Separately, an analysis of 7017 individuals from 6 international studies of gene expression signatures for SBP, diastolic blood pressure (DBP) and hypertension (HTN) found 7717 genes of which 34 were most differentialy expressed. Enrichment analysis for the systolic and diastolic gene group's associated to NK cell mediated cytotoxicity and 13 other pathways including antigen processing and inflammatory response, pointing strongly to innate and adaptive immunity. MYADM was the only gene identified for all groups SBP, DBP and HTN.

MYADM controls endothelial barrier function through ezrin, radixin, and moesin (ERM)-dependent regulation of ICAM-1 expression. ERM expression is required for ICAM-1 expression in response to MYADM suppression or TNF-α. ICAM-1 is a paradigmatic adhesion receptor that regulates leukocyte adhesion together with integrin LFA-1. This connection between endothelial membrane and cortical actin cytoskeleton appears to modulate the inflammatory response at the blood tissue barrier. 

Pressure overload activates the sympathetic nervous system (SNS) and up-regulates p53 expression in the cardiac endothelium and in bone marrow (BM) cells. Increased p53 expression promotes endothelial-leukocyte cell adhesion and initiates inflammation in cardiac tissue, which exacerbates systolic dysfunction. SNS activates, at least by significant increase of circulating norepinephrine (NE), which up-regulates p53 expressions, while forced expression of p53 increased ICAM-1 expression. 

On endothelial cells SNS is mediated via catecholamine-β2-adrenergic signaling, which up-regulates the production of reactive oxygen species (ROS), activates p53 and induces cellular senescence. Immune cells, including macrophages, monocytes, NK cells, B and T cells express the β2-adrenergic receptor and catecholamine. During pressure overload, NE cultured macrophages up-regulated p53 expression, whereas introduction of p53 increased Itgal (LFA-1) expression (which binds ICAM-1). Treatment with NE increased ROS, which was attenuated after inhibition of β2- adrenergic signaling in macrophages. Endothelial cell–macrophage interaction via NE-ROS-p53 signaling induces up-regulation of adhesion molecules, thus contributing to cardiac inflammation and systolic dysfunction.

During hypertension the vascular endothelium activates monocytes, in part through ROS by a loss of nitric oxide (NO) signaling, increased release of IL-6, hydrogen peroxide and a parallel increase in STAT activation in adjacent monocytes. NO inhibits formation of intermediate monocytes and STAT3 activation. Humans with hypertension have increased intermediate and non-classical monocytes and  intermediate monocytes demonstrate evidence of STAT3 activation. Mice with experimental hypertension exhibit increased aortic and renal infiltration of monocytes, dendritic cells, and macrophages with activated STAT3.

A senescence-associated secretory phenotype (SASP) was induced in epithelial cells after DNA damage of sufficient magnitude. In premalignant epithelial cells SASPs induced an epithelial–mesenchyme transition and invasiveness, hallmarks of malignancy by a paracrine mechanism that largely depended interleukin (IL)-6 and IL-8. Strikingly, loss of p53 and gain of oncogenic RAS exacerbated the pro-malignant activities. This suggests a cell-non-autonomous mechanism by which p53 can restrain and oncogenic RAS can promote the development of age-related cancer by altering the tissue microenvironment. Oncogenic signaling pathways inhibit the p53 gene transcription rate through a mechanism involving Stat3, which binds to the p53 promoter in vitro and in vivo. Blocking Stat3 in cancer cells up-regulates expression of p53, leading to p53-mediated tumor cell apoptosis. 

Induced stretch or stretch from pressure overload may engage a non-autonomous, p53 centric micro-mechanical mechanism that escalates or deescalates innate responses against cells functioning outside the mechanical ranges that macrophages or NK cells permit. Thus, the neuro-immune extension through SNS signaling, may begin with circulating blood pressure or stretch promoted through inflammation. 

Genetic Eruption and p53 Response!

L1 are a class of transposable DNA elements found in 17% of the genome that are evolutionarily associated with primitive viral origins. Around 100 have retained the ability to retrotranspose. Without restraint they can interrupt the genome through insertions, deletions, rearrangements, and copy number variations. L1 activity has contributed to instability and evolution of genomes, and is tightly regulated by DNA methylation, histone modifications, and piRNA. They can further impact genome variation by mispairing and unequal crossing-over during meiosis due to its repetitive DNA sequences. Indeed, meiotic double-strand breaks are the proximal trigger for retrotransposon eruptions as highlighted in animals lacking p53.

189 gastrointestinal cancer patients across three cancer types: 95 stomach, colorectal esophageal were examined for any aberration in DNA repair pathways that could be associated with L1 retro-transposition. Out of 15 DNA repair pathways, only the TP53 repair pathway showed a significant association. L1 retro-transposition is inversely correlated with expression of immunologic response genes including interferons. Frequent TP53 mutations in tumors with a higher load of L1 insertions suggest the critical role of TP53 in restricting retrotransposons as a guardian of L1 expression and cancer immunity.

A screen of 172 open reading frames (orfs), of unknown genetic function across several human viruses was designed to discover novel interactions with p53. The orfs encoded viral proteins, miRNA's and lncRNA's. The ORFEOME project was based on the hypothesis that every virus should encode some functions that interfere with the p53 signaling network. The methods present a broad net by screening for interactions without necessarily defining how interactions arise.

The DNA damage response (DDR) pathway stabilizes p53 leading to increased nuclear relocation, binding to p53 response elements, rearrangement of chromatin and transcription of p53 target genes. Any of the multiple p53 related interactions along the way is a potential target of translated viral proteins on the function of p53. 

p53 is also induced in response to viral infections as a downstream transcriptional target of type I interferon (IFN) signaling. Cells with functional p53 exhibited markedly decreased viral replication early after infection. This early inhibition of viral replication was mediated both in vitro and in vivo by a p53-dependent enhancement of IFN signaling by the induction of genes containing IFN-stimulated response elements. p53 also contributed to an increase in IFN release from infected cells. This p53-dependent enhancement of IFN signaling is dependent to a great extent on p53 activation and transcription of IFN regulatory factor 9, a central component of the IFN-stimulated gene factor 3 complex. Thus p53 contributes to innate immunity by enhancing IFN-dependent antiviral activity independent of its functions as a proapoptotic and tumor suppressor gene.

p53 likely cooperates with histone and DNA methylation to silence specific retroelements. In the zebrafish model, it was shown that p53-dependent H3K9me3 methylation, in the promoter region of a synthetic human LINE1 element mapped to a known p53-binding site. Some evidence in human cell lines suggests that p53 can physically interact with both H3K9 tri-methyltransferases and DNA methyltransferases. In basal stress-free conditions, unacetylated p53 is pre-bound to many target genes together with SET - a repressor protein, which mediates repression of p53 target genes. Additionally, p53 as a master regulator of transcription might regulate gene expression of key epigenetic or piRNA factors. 

Through L1's we get a sense of p53's interconnectedness to DNA damage, viral replication, cancer and immunity. In a way we can sympathize with it, especially when overloaded by viral infiltration and eruption. Its understandable how, under those conditions double stranded DNA breaks and pathway impediments compromise its ability to be guardian of the genome!