Alterations In Epigenetic Landscape Research Articles

Histone Chaperone Deficiency in Arabidopsis Plants Triggers Adaptive Epigenetic Changes in Histone Variants and Modifications

At the molecular scale, adaptive advantages during plant growth and development rely on modulation of gene expression, primarily provided by epigenetic machinery. One crucial part of this machinery is histone posttranslational modifications, which form a flexible system, driving transient changes in chromatin, and defining particular epigenetic states. Posttranslational modifications work in concert with replication-independent histone variants further adapted for transcriptional regulation and chromatin repair. However, little is known about how such complex regulatory pathways are orchestrated and interconnected in cells. In this work, we demonstrate the utility of mass spectrometry–based approaches to explore how different epigenetic layers interact in Arabidopsis mutants lacking certain histone chaperones. We show that defects in histone chaperone function (e.g., chromatin assembly factor-1 or nucleosome assembly protein 1 mutations) translate into an altered epigenetic landscape, which aids the plant in mitigating internal instability. We observe changes in both the levels and distribution of H2A.W.7, altogether with partial repurposing of H3.3 and changes in the key repressive (H3K27me1/2) or euchromatic marks (H3K36me1/2). These shifts in the epigenetic profile serve as a compensatory mechanism in response to impaired integration of the H3.1 histone in the fas1 mutants. Altogether, our findings suggest that maintaining genome stability involves a two-tiered approach. The first relies on flexible adjustments in histone marks, while the second level requires the assistance of chaperones for histone variant replacement.

Abstract LB286: Extrachromosomal DNA in lung cancer from never smokers

Abstract Extrachromosomal DNA (ecDNA), circular DNA that resides outside of the linear chromosome, is a potent form of oncogene amplification in cancer. The structure and properties of ecDNA are markedly different from those of linear DNA, characterized by features like non-Mendelian inheritance and an altered epigenetic landscape. A prior pan-cancer analysis ​​indicated patients with cancers harboring ecDNA have statistically worse overall survival when compared to cancer patients with other types of focal amplification. Moreover, its unique characteristics also make it a promising target for therapy. Recently, efforts have intensified to profile ecDNA across many cancer types, yet comprehensive studies of ecDNA in lung cancer in never smokers (LCINS) is lacking. Given that LCINS is partially driven by somatic copy number alterations, we hypothesized that ecDNA-driven focal amplifications significantly influence LCINS tumor evolution. As part of the Sherlock-Lung project (current data freeze, 1217 samples), we comprehensively profiled 871 treatment-naive samples using a robust computational pipeline that refined copy number segmentation by accounting for tumor purity and ploidy. ecDNA was present in 151 (17.3%) of tumor samples, with a third of ecDNA-positive samples harboring more than one distinct ecDNA amplicon. Consistent with prior reports, no ecDNA was found in bulk sequenced blood or matched normal lung tissues. These ecDNA often included genes (84%), frequently overlapping with known oncogenes like MDM2, TERT, and MYC, which showed higher expression levels compared to non-amplified or other amplified genes. Notably, most MDM2 amplifications (36/45) were on ecDNA. ecDNA was significantly associated with whole genome doubling, tumor stage, and several endogenous mutational signatures, including APOBEC (SBS2 and SBS13), and clock-like signature (SBS1). Intriguingly, ecDNA-positive tumors were associated with significantly worse survival compared to tumors without any focal amplifications, though tumors with other amplification types (e.g. breakage-fusion-bridge, linear amplification, or complex events) had similar survival impacts. The unprecedented size of our cohort and the integration of clinical, epidemiologic, and multi-omics data allowed us to perform the first in-depth characterization of ecDNA in LCINS. We reconstructed the genomic regions involved in ecDNA and revealed the full spectrum of simple and complex ecDNAs across cancer histologies as well as the clinical and functional impact of ecDNA on LCINS. Citation Format: Azhar Khandekar, Tongwu Zhang, Marcos Diaz-Gay, Jens Luebeck, Ludmil Alexandrov, Maria Landi. Extrachromosomal DNA in lung cancer from never smokers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB286.

Abstract SY03-03: Thinking outside the chromosome: Interrogating epigenetic mechanisms in noncanonical chromatin species

Abstract The epigenetic regulation of DNA-templated processes is intricately tied to numerous events that determine cell phenotype and fate. The abrogation of epigenetic cascades drives various disease states, including cancer. Many of these pathological phenomena involve major chromosomal arrangements that can include the generation of non-canonical chromatin structures existing in the primary nuclei or encapsulated in spatially distinct micronuclei. Recently, we undertook a mechanistic approach to investigate the properties of unique non-chromosomal structures, revealing significant epigenetic contributions to their regulation. We found that micronuclei, the result of chromosomal instability in cancer, assume altered epigenetic landscapes upon departure from the nucleus. Moreover, chromosomes sequestered in micronuclei retain the epigenetic "scars" after reintegration into the primary nucleus, contributing to epigenetic reprogramming and heterogeneity in cancer. Additionally, we turned our attention to the Hepatitis B Virus' (HBV) covalently closed circular DNA (cccDNA) minichromosome, which forms from viral DNA and human histones following infection. We found that chromatinization drives the expression of the key viral oncogene, HBx, and thus promotes viral infection. Elucidating this new mechanism enabled us to halt infection by inhibiting histone remodeling, creating a potential first-in-class therapy for HBV. These exciting findings demonstrate the key role of chromatin in biomedical events and how a fundamental understanding of these processes can lead to the identification of new therapeutic avenues. Citation Format: Yael David. Thinking outside the chromosome: Interrogating epigenetic mechanisms in noncanonical chromatin species [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr SY03-03.

Abstract 1719: Targeting H3.3 serine 28 phosphorylation as a novel therapeutic strategy for diffuse midline glioma

Abstract Background: Diffuse midline glioma (DMG) is a highly aggressive pediatric brain cancer with a poor prognosis [1]. Mechanistically, DMG harbors a lysine-to-methionine substitution at position 27 of histone H3.3 (H3.3K27M), which leads to global hypomethylation and a dramatically altered epigenetic landscape [2, 3]. Aim: This study aims to explore the H3.3K27M mutation from a novel perspective by investigating its effects on H3.3 ubiquitination, with the goal of identifying effective, novel therapeutic targets. Methods: Mass spectrometry was used to identify potential E3 ligases for H3.3, while immunoprecipitation to verify this interaction. Cell viability and survival were determined by MTS and clonogenic survival assays, respectively. Nucleosome fractionation was performed to detect the distribution of wild-type (WT) or K27M mutant H3.3 histones. Results: Mass spectrometry identified UBR7, an E3 ligase, as exhibiting a stronger binding affinity with WT H3.3 than its K27M mutant counterpart. Further nucleosome fractionation assay revealed that K27M histones are more likely deposited in nucleosomes than WT H3.3. Further analysis demonstrated that a non-phosphorylation mimic mutation (serine to alanine) at amino acid 28 (S28A) restored the binding affinity of K27M mutant H3.3 with UBR7. Importantly, this mutation disrupted H3.3 phosphorylation and significantly diminished cell survival, whereas the constitutively activated phosphorylation mutation (S to glutamine (E)) on S28 (S28E) mimics K27M mutation in promoting cell proliferation and survival. Conclusion: These findings suggest that S28ph impairs UBR7-mediated K27M ubiquitination and promotes DMG cell growth, suggesting that targeting S28ph is an effective therapeutic strategy. However, the underlying mechanisms by which K27M interplays with S28ph in promoting tumorigenesis require further investigation. Citation Format: Yuqian Yan. Targeting H3.3 serine 28 phosphorylation as a novel therapeutic strategy for diffuse midline glioma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1719.

Pudgy mouse rib deformities emanate from abnormal paravertebral longitudinal cartilage/bone accumulations.

The pudgy (pu/pu) mouse, caused by a recessive mutation in the Notch family Delta like-3 gene (Dll3), has severe rib, vertebral body and intervertebral disc abnormalities. Using whole-mount preparations and serial histologic sections we demonstrate: 1) localized paravertebral longitudinal cartilage/bone accumulations (PVLC/BAs) invariably associated with branched, fused and asymmetrically spaced ribs that emanate from it laterally; 2) abnormal rib formation immediately adjacent to abnormal vertebral body and intervertebral disc formation in asymmetric right/left fashion; and 3) patterns of rib deformation that differ in each mouse. Normal BALB/c embryo and age-matched non-affected pu/+ mice assessments allow for pu/pu comparisons. The Dll3 Notch family gene is involved in normal somitogenesis via the segmentation clock mechanism. Although pathogenesis of rib deformation is initially triggered by the Dll3 gene mutation, these findings of abnormal asymmetric costo-vertebral region structure imply that differing patterns cannot be attributed to this single gene mutation alone. All findings implicate a dual mechanism of malformation: the Dll3 gene mutation leading to subtle timing differences in traveling oscillation waves of the segmentation clock and further subsequent misdirection of tissue formation by altered chemical reaction-diffusion and epigenetic landscape responses. PVLC/BAs appear as primary supramolecular structures underlying severe rib malformation associated both with time-sensitive segmentation clock mutations and subsequent reactions.

Frontiers in aging special issue: DNA repair and interventions in aging perspective on "loss of epigenetic information as a cause of mammalian aging".

The recently published article in Cell by the Sinclair lab and collaborators entitled "Loss of Epigenetic Information as a Cause of Mammalian Aging" [1] implicates heritable changes in gene expression as the basis for aging, a postulate consistent with the emerging information theory of aging. Sinclair's group and colleagues induced epigenetic changes, i.e., DNA and histone modifications, via double-strand breaks (DSBs) catalyzed by the I-Pol endonuclease at specific genomic loci. The genomic DNA breaks, introduced without inducing insertion or deletion mutations (indels) in a mouse model, were targeted to 19 non-coding regions and one region in ribosomal DNA (rDNA), the latter shown to not have a significant effect on the function or transcription of rDNA [1]. With that experimental model in place, the authors present experimental evidence supporting a model that epigenetic changes drive aging via this inducible DNA break mechanism. After demonstrating the phenotypic alterations of this accelerated aging, they attempt to reverse selective phenotypes by resetting the altered epigenetic landscape. Establishing a causal relationship between epigenetic changes and aging, and how this connection might be manipulated to overturn cellular features of aging, is provocative and merits further study.

Targeting KDM2A Enhances T-cell Infiltration in NSD1-Deficient Head and Neck Squamous Cell Carcinoma.

The altered epigenetic landscape of NSD1-deficient tumors confers sensitivity to inhibition of the histone-modifying enzyme KDM2A as an immunotherapeutic strategy to stimulate T-cell infiltration and suppress tumor growth.

New Biomarkers and Treatment Advances in Triple-Negative Breast Cancer.

Triple-negative breast cancer (TNBC) is a specific subtype of breast cancer lacking hormone receptor expression and HER2 gene amplification. TNBC represents a heterogeneous subtype of breast cancer, characterized by poor prognosis, high invasiveness, high metastatic potential, and a tendency to relapse. In this review, the specific molecular subtypes and pathological aspects of triple-negative breast cancer are illustrated, with particular attention to the biomarker characteristics of TNBC, namely: regulators of cell proliferation and migration and angiogenesis, apoptosis-regulating proteins, regulators of DNA damage response, immune checkpoints, and epigenetic modifications. This paper also focuses on omics approaches to exploring TNBC, such as genomics to identify cancer-specific mutations, epigenomics to identify altered epigenetic landscapes in cancer cells, and transcriptomics to explore differential mRNA and protein expression. Moreover, updated neoadjuvant treatments for TNBC are also mentioned, underlining the role of immunotherapy and novel and targeted agents in the treatment of TNBC.

Targeted Epigenetic Interventions in Cancer with an Emphasis on Pediatric Malignancies.

Over the past two decades, novel hallmarks of cancer have been described, including the altered epigenetic landscape of malignant diseases. In addition to the methylation and hyd-roxymethylation of DNA, numerous novel forms of histone modifications and nucleosome remodeling have been discovered, giving rise to a wide variety of targeted therapeutic interventions. DNA hypomethylating drugs, histone deacetylase inhibitors and agents targeting histone methylation machinery are of distinguished clinical significance. The major focus of this review is placed on targeted epigenetic interventions in the most common pediatric malignancies, including acute leukemias, brain and kidney tumors, neuroblastoma and soft tissue sarcomas. Upcoming novel challenges include specificity and potential undesirable side effects. Different epigenetic patterns of pediatric and adult cancers should be noted. Biological significance of epigenetic alterations highly depends on the tissue microenvironment and widespread interactions. An individualized treatment approach requires detailed genetic, epigenetic and metabolomic evaluation of cancer. Advances in molecular technologies and clinical translation may contribute to the development of novel pediatric anticancer treatment strategies, aiming for improved survival and better patient quality of life.

DNA methylome in pancreatic cancer identified novel promoter hyper-methylation in NPY and FAIM2 genes associated with poor prognosis in Indian patient cohort

BackgroundPancreatic ductal adenocarcinoma (PDAC) is one of the leading cancers worldwide and has a poor survival, with a 5-year survival rate of only 8.5%. In this study we investigated altered DNA methylation associated with PDAC severity and prognosis.MethodsMethylome data, generated using 450 K bead array, was compared between paired PDAC and normal samples in the TCGA cohort (n = 9) and our Indian cohort (n = 7). The total Indian Cohort (n = 75) was split into cohort 1 (n = 7), cohort 2 (n = 22), cohort 3 (n = 26) and cohort 4 (n = 20).Validation of differential methylation (6 selected CpG loci) and associated gene expression for differentially methylated genes (10 selected gDMs) were carried out in separate validation cohorts, using MSP, RT-PCR and IHC correlations between methylation and gene expression were observed in TCGA, GTEx cohorts and in validation cohorts. Kaplan–Meier survival analysis was done to study differential prognosis, during 2–5 years of follow-up.ResultsWe identified 156 DMPs, mapped to 91 genes (gDMs), in PDAC; 68 (43.5%) DMPs were found to be differentially methylated both in TCGA cohort and our cohort, with significant concordance at hypo- and hyper-methylated loci. Enrichments of “regulation of ion transport”, “Interferon alpha/beta signalling”, “morphogenesis and development” and “transcriptional dysregulation” pathways were observed among 91 gDMs. Hyper-methylation of NPY and FAIM2 genes with down-regulated expression in PDAC, were significantly associated with poor prognosis in the Indian patient cohort.ConclusionsEthnic variations among populations may determine the altered epigenetic landscape in the PDAC patients of the Indian cohort. Our study identified novel differentially methylated genes (mainly NPY and FAIM2) and also validated the previously identified differentially methylated CpG sites associated with PDAC cancer patient’s survival. Comparative analysis of our data with TCGA and CPTAC cohorts showed that both NPY and FAIM2 hyper-methylation and down-regulations can be novel epigenetically regulated genes in the Indian patient population, statistically significantly associated with poor survival and advanced tumour stages.

Extrachromosomal DNA amplifications in cancer.

Extrachromosomal DNA (ecDNA) amplification is an important driver alteration in cancer. It has been observed in most cancer types and is associated with worse patient outcome. The functional impact of ecDNA has been linked to its unique properties, such as its circular structure that is associated with altered chromatinization and epigenetic regulatory landscape, as well as its ability to randomly segregate during cell division, which fuels intercellular copy number heterogeneity. Recent investigations suggest that ecDNA is structurally more complex than previously anticipated and that it localizes to specialized nuclear bodies (hubs) and can act in trans as an enhancer for genes on other ecDNAs or chromosomes. In this Review, we synthesize what is currently known about how ecDNA is generated and how its genetic and epigenetic architecture affects proto-oncogene deregulation in cancer. We discuss how recently identified ecDNA functions may impact oncogenesis but also serve as new therapeutic vulnerabilities in cancer.

The m6A methyltransferase Mettl3 deficiency attenuates hepatic stellate cell activation and liver fibrosis

Activation of hepatic stellate cells (HSCs) is a central driver of liver fibrosis. Previous investigations have identified various altered epigenetic landscapes during the cellular progression of HSC activation. N6-methyladenosine (m6A) is the most abundant internal RNA modification in eukaryotic cells and is dynamically regulated under various physiological and pathophysiological conditions. However, the functional role of Mettl3-mediated m6A in liver fibrosis remains elusive. Here, we found that the HSC-specific knockout of m6A methyltransferase Mettl3 suppressed HSC activation and significantly alleviated liver fibrosis. Multi-omics analysis of HSCs showed that Mettl3 depletion reduced m6A deposition on mRNA transcripts of Lats2 (a central player of the Hippo/YAP signaling pathway) and slowed down their degradation. Elevated Lats2 increased phosphorylation of the downstream transcription factor YAP, suppressed YAP nuclear translocation, and decreased pro-fibrotic gene expression. Overexpressing YAP mutant resistant to phosphorylation by Lats2 partially rescued the activation and pro-fibrotic gene expression of Mettl3-deficientHSCs. Our study revealed that disruption of Mettl3 in HSCs mitigated liver fibrosis by controlling the Hippo/YAP signaling pathway, providing potential therapeutic strategies to alleviate liver fibrosis by targeting epitranscriptomic machinery.

Role of Flavonoids as Epigenetic Modulators in Cancer Prevention and Therapy.

Epigenetic regulation involves reversible changes in histones and DNA modifications that can be inherited without any changes in the DNA sequence. Dysregulation of normal epigenetic processes can lead to aberrant gene expression as observed in many diseases, notably cancer. Recent insights into the mechanisms of DNA methylation, histone modifications, and non-coding RNAs involved in altered gene expression profiles of tumor cells have caused a paradigm shift in the diagnostic and therapeutic approaches towards cancer. There has been a surge in search for compounds that could modulate the altered epigenetic landscape of tumor cells, and to exploit their therapeutic potential against cancers. Flavonoids are naturally occurring phenol compounds which are abundantly found among phytochemicals and have potentials to modulate epigenetic processes. Knowledge of the precise flavonoid-mediated epigenetic alterations is needed for the development of epigenetics drugs and combinatorial therapeutic approaches against cancers. This review is aimed to comprehensively explore the epigenetic modulations of flavonoids and their anti-tumor activities.

Super-Enhancer-Driven PPP1R15B As an Oncogenic and Potential Therapeutic Target in Multiple Myeloma

Background: Multiple myeloma (MM) is a hematological malignancy arising from immunoglobulin-secreting plasma cells. Despite recent progress in stem-cell transplantation, high-dose chemotherapy and novel therapies, MM remains incurable and most patients experience relapse. In addition of genetic alterations, growing evidence has suggested that alterations in epigenetic landscape contribute to pathogenesis of MM. Super enhancers (SE) are large clusters of putative enhancers with aberrantly strong binding of mediators and transcription-regulating proteins. MM cells are highly dependent on unfolded protein response (UPR) signaling pathways due to high level of endoplasmic reticulum (ER) stress. Phosphorylation of eIF2α can attenuate protein translation. The PPP1R15B (denoted as R15B hereafter) gene encodes a regulatory subunit of an eIF2α-specific phosphatase complex. In this study, we identified SE-driven oncogenes specific in MM with a particular focus on a candidate SE-associated gene R15B, whose functional roles in MM remain largely elusive.Methods: We performed H3K27Ac ChIP-seq on MM cell lines, primary MM patient samples and normal CD138+ plasma cells, memory B cells (controls). ROSE analysis was used to systematically annotate SEs and their associated genes between tumors and controls. A combination of public data mining, RNA interference (RNAi), overexpression and CRISPR/Cas9 technologies followed by functional assays were conducted to determine the oncogenic effects of R15B in MM. Transcriptome analysis of MM cell line NCI-H929 with R15B knockdown and scrambled control was performed. To further study the interactions between SE and its promoters, we are currently working on highly integrative chromatin immunoprecipitation (HiChIP) followed by sequencing.Results: We have identified R15B as one of the SE-associated genes specific to MM patient samples and MM cell lines. The expression of R15B was 6- to 50-fold higher in a panel of 8 MM cell lines than normal controls. SE activity was correlated with the expression level of R15B. Higher expression of R15B predicted poor overall survival of MM patients, suggesting its clinical relevance in MM pathogenesis. Knockdown and knockout of R15B significantly reduced cell viability, clonogenicity and induced G2/M phase cell cycle arrest. Gene Ontology (GO) enrichment and pathway analysis of downregulated genes in response to R15B knockdown indicates that these genes are significantly associated with G2/M checkpoint hallmark, oxidative phosphorylation, unfolded protein response and E2F1-related pathways. Loss of R15B may induce apoptosis via activation of UPR pro-apoptotic executors PUMA and NOXA. ChIP-qPCR assays indicates that transcription factor C/EBP-β is strongly enriched at R15B SE region. Furthermore, we examined the therapeutic effects of Salubrinal, a selective inhibitor of eIF2α phosphorylation, on MM cells. Salubrinal inhibited MM cell proliferation in a dose-dependent manner, and MM cell lines with higher R15B expression were more sensitive to Salubrinal than those with lower R15B level.Conclusions: Our integrative approaches identified R15B as a novel SE-driven oncogene, and may form a positive feedback loop with C/EBP-β. Salubrinal selectively inhibits proliferation of MM cells with high R15B expression. Hence, we propose that targeting R15B may serve as a new approach for effective anti-myeloma therapy, which warrants further clinical investigation. DisclosuresChng: Novartis: Honoraria; Celgene: Honoraria, Research Funding; Janssen: Honoraria, Research Funding; Abbvie: Honoraria; Amgen: Honoraria, Research Funding.

P-098: Super-enhancer-driven PPP1R15B as an oncogenic and potential therapeutic target in Multiple Myeloma

<h3>Background</h3> Growing evidence suggests that alterations in epigenetic landscape contribute to pathogenesis of multiple myeloma (MM). MM cells are highly dependent on unfolded protein response signaling pathways due to high level of endoplasmic reticulum stress. Phosphorylation of eIF2a can attenuate protein translation. The PPP1R15B(denoted as R15B hereafter) gene encodes a regulatory subunit of eIF2a-specific phosphatase complex. In this study,we identified super enhancer (SE)-driven oncogenes specific in MM with a particular focus on a candidate gene R15B, whose functional roles in MM remain largely elusive. <h3>Methods</h3> We performed H3K27Ac ChIP-seq on MM cell lines, primary MM patient samples, normal CD138+ plasma cells and memory B cells. ROSE analysis was used to annotate SEs and their associated genes. A combination of public data mining, RNAi, overexpression and CRISPR/Cas9 technologies were conducted to determine the oncogenic effects of R15B in MM. Transcriptome analysis of MM cell line H929 with R15B KD and scrambled control was performed. To further study the interactions between SE and its promoters, we are currently working on HiChIP. <h3>Results</h3> We have identified R15B as one of the SE-associated genes specific to MM patient samples and cell lines. SE activity was correlated with the expression level of R15B. Higher expression of R15B predicted poor overall survival of MM patients, suggesting its clinical relevance in MM pathogenesis. R15B KD or KO significantly reduced cell viability, clonogenicity and induced G2/M arrest. ChIP-qPCR assays showed that C/EBP-β is strongly enriched at R15B SE region. We also found that salubrinal, a selective inhibitor of eIF2a phosphorylation, inhibited MM cell proliferation in a dose-dependent manner. <h3>Conclusions</h3> Our integrative approaches identified R15B as a novel SE-driven oncogene. We propose that targeting R15B may serve as a new approach for effective anti-myeloma therapy, which warrants further clinical investigation.

An Assessment on Ethanol-Blended Gasoline/Diesel Fuels on Cancer Risk and Mortality.

Although cancer is traditionally considered a genetic disease, the epigenetic abnormalities, including DNA hypermethylation, histone deacetylation, and/or microRNA dysregulation, have been demonstrated as a hallmark of cancer. Compared with gene mutations, aberrant epigenetic changes occur more frequently, and cellular epigenome is more susceptible to change by environmental factors. Excess cancer risks are positively associated with exposure to occupational and environmental chemical carcinogens, including those from gasoline combustion exhausted in vehicles. Of note, previous studies proposed particulate matter index (PMI) as a measure for gasoline sooting tendency, and showed that, compared with the other molecules in gasoline, 1,2,4–Trimethylbenzene, 2–methylnaphthalene and toluene significantly contribute to PMI of the gasoline blends. Mechanistically, both epigenome and genome are important in carcinogenicity, and the genotoxicity of chemical agents has been thoroughly studied. However, less effort has been put into studying the epigenotoxicity. Moreover, as the blending of ethanol into gasoline substitutes for carcinogens, like benzene, toluene, xylene, butadiene, and polycyclic aromatic hydrocarbons, etc., a reduction of secondary aromatics has been achieved in the atmosphere. This may lead to diminished cancer initiation and progression through altered cellular epigenetic landscape. The present review summarizes the most important findings in the literature on the association between exposures to carcinogens from gasoline combustion, cancer epigenetics and the potential epigenetic impacts of biofuels.

Diet-Dependent Metabolic Regulation of DNA Double-Strand Break Repair in Cancer: More Choices on the Menu.

Despite several epidemiologic and preclinical studies supporting the role of diet in cancer progression, the complexity of the diet-cancer link makes it challenging to deconvolute the underlying mechanisms, which remain scantly elucidated. This review focuses on genomic instability as one of the cancer hallmarks affected by diet-dependent metabolic alterations. We discuss how altered dietary intake of metabolites of the one-carbon metabolism, including methionine, folate, and vitamins B and C, can impact the methylation processes and thereby tumorigenesis. We present the concept that the protumorigenic effect of certain diets, such as the Western diet, is in part due to a diet-induced erosion of the DNA repair capacity caused by altered epigenetic and epitranscriptomic landscapes, while the protective effect of other dietary patterns, such as the Mediterranean diet, can be partly explained by their ability to sustain a proficient DNA repair. In particular, considering that diet-dependent alterations of the one-carbon metabolism can impact the rate of methylation processes, changes in dietary patterns can affect the activity of writers and erasers of histone and RNA methyl marks and consequently impair their role in ensuring a proficient DNA damage repair.

Investigating the Roles of the Yeats Domain in MLL-ENL Mediated Leukemogenesis

Approximately 10% of acute leukemia involves rearrangement at chromosome 11q23, giving rise to a relatively aggressive form of acute leukemia characterized by MLL1 (KMT2A) fusion proteins. Despite the identification of &amp;gt;100 MLL1 fusion partners, the majority are members of several similar transcriptional activation complexes including: The Super Elongation Complex (SEC), AEP and EAP (SEC used hereafter). MLL fusion-driven acute leukemia is characterized by deregulated activity of the SEC and the H3K79 methyltransferase DOT1L. This leads to altered epigenetic landscapes at and deregulated transcription of pro-leukemic MLL1-fusion target genes like HoxA9 and Meis1. Thus, targeting these transcriptional and epigenetic complexes has become an attractive therapeutic strategy for treating MLL-fusion leukemia. Eleven-Nineteen-Leukemia (ENL or MLLT1) is the third most common MLL1 fusion partner and a component of the SEC. Recently, wild type ENL was identified as an essential factor for leukemic cell growth. The ENL protein possesses a C-terminal ANC-homology domain (AHD) necessary for SEC recruitment and is essential for MLL-fusion mediated leukemogenesis. In addition, ENL contains a highly conserved N-terminal YEATS domain that functions as an epigenetic reader for acetylated H3K9, H3K18 or H3K27, which is essential for leukemic cell growth. Additionally, the ENL YEATS domain directly interacts with the Polymerase Associated Factor 1 complex (PAF1c), an epigenetic regulator protein complex essential for MLL-fusion mediated leukemogenesis. These studies highlight the importance of the YEATS domain in regulating wild type ENL function in leukemic cells. However, the importance of the YEATS domain in the context of MLL-ENL mediated leukemia remains to be elucidated. In this study, we investigate the clinical relevance and leukemic importance of the ENL YEATS domain in MLL-ENL leukemias. We first analyzed t(11;19) (MLL-ENL) patient data to determine the sites of chromosomal translocation within the ENL gene. We found that the YEATS domain (coded by exons 2 through 4) is retained in 84.1% of MLL-ENL patients (n=302). Specifically, 50.7% (n=153) of these patients possess breakpoints located 5' of the first exon of the ENL gene, while 33.4% (n=101) of the patients display breakpoints within the first intron of ENL gene. These data point towards a tendency for YEATS domain retention in MLL-ENL fusion proteins in t(11;19) patients. We next tested whether the YEATS domain was functional in MLL-ENL mouse leukemia models. Our data shows the YEATS domain is required for MLL-ENL leukemogenesis in vivo, as deletion of the YEATS domain destroys MLL-ENL leukemogenesis and increases apoptosis in cell culture. Transcriptionally, deletion of the YEATS domain decreased expression of pro-leukemic genes such as Meis1 and the anti-apoptotic gene Bclxl. To dissect the contribution of different YEATS domain functions in MLL-ENL leukemogenesis, we engineered YEATS domain mutants defective in interacting with PAF1 or acetylated H3K9/K18/K27. Disrupting the YEATS-PAF1 or YEATS-H3Kac interaction decreased MLL-ENL mediated colony formation exvivo and significantly increased leukemia latency in vivo. The MLL-ENL YEATS domain mutants will be used in future studies to determine how the YEATS domain affects 1) MLL-ENL fusion localization, 2) key protein complexes localization (i.e. SEC and PAF1c) and 3) the epigenetic landscapes (i.e. H3K79me2/3 and H3K4me3) at pro-leukemic targets. To further interrogate the YEATS-PAF1 interaction in MLL-ENL mediated leukemia, we identified the minimal region of the PAF1 protein required for the YEATS-PAF1 interaction. This PAF1 protein fragment will be used to biochemically characterize the structure of the PAF1-YEATS interaction, which might aid in therapeutically targeting specific YEATS interactions in MLL-ENL leukemia. Our results demonstrate for the first time, to our knowledge, an essential role for the YEATS domain in MLL-ENL mediated leukemogenesis. Additionally, our genetic studies elucidate the importance of the YEATS domain interaction with either the PAF1c or H3Kac in MLL-ENL leukemias. Taken together, our study establishes a rationale for exploring the effectiveness of small molecule development aimed at disrupting either the YEATS-H3Kac or the YEATS-PAF1 interaction as a therapeutic intervention for treating MLL-ENL leukemia patients. Disclosures No relevant conflicts of interest to declare.

Metabolic and epigenetic regulation of T-cell exhaustion

Current immunotherapies yield remarkable clinical outcomes by boosting the power of host immunity in cancer cell elimination and viral clearance. However, after prolonged antigen exposure, CD8+ T cells differentiate into a special differentiation state known as T-cell exhaustion, which poses one of the major hurdles to antiviral and antitumor immunity during chronic viral infection and tumour development. Growing evidence indicates that exhausted T cells undergo metabolic insufficiency with altered signalling cascades and epigenetic landscapes, which dampen effector immunity and cause poor responsiveness to immune-checkpoint-blockade therapies. How metabolic stress affects T-cell exhaustion remains unclear; therefore, in this Review, we summarize current knowledge of how T-cell exhaustion occurs, and discuss how metabolic insufficiency and prolonged stress responses may affect signalling cascades and epigenetic reprogramming, thus locking T cells into an exhausted state via specialized differentiation programming.

Genomic diversifications of five Gossypium allopolyploid species and their impact on cotton improvement

Polyploidy is an evolutionary innovation for many animals and all flowering plants, but its impact on selection and domestication remains elusive. Here we analyze genome evolution and diversification for all five allopolyploid cotton species, including economically important Upland and Pima cottons. Although these polyploid genomes are conserved in gene content and synteny, they have diversified by subgenomic transposon exchanges that equilibrate genome size, evolutionary rate heterogeneities and positive selection between homoeologs within and among lineages. These differential evolutionary trajectories are accompanied by gene-family diversification and homoeolog expression divergence among polyploid lineages. Selection and domestication drive parallel gene expression similarities in fibers of two cultivated cottons, involving coexpression networks and N6-methyladenosine RNA modifications. Furthermore, polyploidy induces recombination suppression, which correlates with altered epigenetic landscapes and can be overcome by wild introgression. These genomic insights will empower efforts to manipulate genetic recombination and modify epigenetic landscapes and target genes for crop improvement.