1 5971 136 TET PROTEINS AND 5-METHYLCYTOSINE OXIDATION IN HEMATOLOGICAL CANCERS. DNA METHYLATION HAS PIVOTAL REGULATORY ROLES IN MAMMALIAN DEVELOPMENT, RETROTRANSPOSON SILENCING, GENOMIC IMPRINTING, AND X-CHROMOSOME INACTIVATION. CANCER CELLS DISPLAY HIGHLY DYSREGULATED DNA METHYLATION PROFILES CHARACTERIZED BY GLOBAL HYPOMETHYLATION IN CONJUNCTION WITH HYPERMETHYLATION OF PROMOTER CPG ISLANDS THAT PRESUMABLY LEAD TO GENOME INSTABILITY AND ABERRANT EXPRESSION OF TUMOR SUPPRESSOR GENES OR ONCOGENES. THE RECENT DISCOVERY OF TEN-ELEVEN-TRANSLOCATION (TET) FAMILY DIOXYGENASES THAT OXIDIZE 5MC TO 5-HYDROXYMETHYLCYTOSINE (5HMC), 5-FORMYLCYTOSINE (5FC), AND 5-CARBOXYLCYTOSINE (5CAC) IN DNA HAS LED TO PROFOUND PROGRESS IN UNDERSTANDING THE MECHANISM UNDERLYING DNA DEMETHYLATION. AMONG THE THREE TET GENES, TET2 RECURRENTLY UNDERGOES INACTIVATING MUTATIONS IN A WIDE RANGE OF MYELOID AND LYMPHOID MALIGNANCIES. TET2 FUNCTIONS AS A BONA FIDE TUMOR SUPPRESSOR PARTICULARLY IN THE PATHOGENESIS OF MYELOID MALIGNANCIES RESEMBLING CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML) AND MYELODYSPLASTIC SYNDROMES (MDS) IN HUMAN. HERE WE REVIEW DIVERSE FUNCTIONS OF TET PROTEINS AND THE NOVEL EPIGENETIC MARKS THAT THEY GENERATE IN DNA METHYLATION/DEMETHYLATION DYNAMICS AND NORMAL AND MALIGNANT HEMATOPOIETIC DIFFERENTIATION. THE IMPACT OF TET2 INACTIVATION IN HEMATOPOIESIS AND VARIOUS MECHANISMS MODULATING THE EXPRESSION OR ACTIVITY OF TET PROTEINS ARE ALSO DISCUSSED. FURTHERMORE, WE ALSO PRESENT EVIDENCE THAT TET2 AND TET3 COLLABORATE TO SUPPRESS ABERRANT HEMATOPOIESIS AND HEMATOPOIETIC TRANSFORMATION. A DETAILED UNDERSTANDING OF THE NORMAL AND PATHOLOGICAL FUNCTIONS OF TET PROTEINS MAY PROVIDE NEW AVENUES TO DEVELOP NOVEL EPIGENETIC THERAPIES FOR TREATING HEMATOLOGICAL MALIGNANCIES. 2015 2 6419 36 THE TET2-UPF1 COMPLEX MODULATES MRNA STABILITY UNDER STRESS CONDITIONS. INTRODUCTION: ENVIRONMENTAL STRESS PROMOTES EPIGENETIC ALTERATIONS THAT IMPACT GENE EXPRESSION AND SUBSEQUENTLY PARTICIPATE IN THE PATHOLOGICAL PROCESSES OF THE DISORDER. AMONG EPIGENETIC REGULATIONS, TEN-ELEVEN TRANSLOCATION (TET) ENZYMES OXIDIZE 5-METHYLCYTOSINE (5MC) TO 5-HYDROXYMETHYLCYTOSINE (5HMC) IN DNA AND RNA AND FUNCTION AS CRITICAL PLAYERS IN THE PATHOGENESIS OF DISEASES. OUR PREVIOUS RESULTS SHOWED THAT CHRONIC STRESS INCREASES THE EXPRESSION OF CYTOPLASMIC TET2 IN THE HIPPOCAMPUS OF MICE EXPOSED TO CHRONIC MILD STRESS (CMS). WHETHER THE CYTOPLASMIC TET2 ALTERS RNA 5HMC MODIFICATION IN CHRONIC STRESS-RELATED PROCESSES REMAINS LARGELY UNKNOWN. METHODS: TO EXPLORE THE ROLE OF CYTOPLASMIC TET2 UNDER CMS CONDITIONS, WE ESTABLISHED CMS MICE MODEL AND DETECTED THE EXPRESSION OF RNA 5HMC BY DOT BLOT. WE VERIFIED THE INTERACTION OF TET2 AND ITS INTERACTING PROTEIN BY CO-IMMUNOPRECIPITATION COMBINED WITH MASS SPECTROMETRY AND SCREENED DOWNSTREAM TARGET GENES BY CLUSTER ANALYSIS OF TET2 AND UPSTREAM FRAMESHIFT 1 (UPF1) INTERACTING RNA. THE EXPRESSION OF PROTEIN WAS DETECTED BY WESTERN BLOT AND THE EXPRESSION OF THE SCREENED TARGET GENES WAS DETECTED BY QRT-PCR. RESULTS: IN THIS STUDY, WE FOUND THAT INCREASED CYTOPLASMIC TET2 EXPRESSION UNDER CMS CONDITIONS LEADS TO INCREASE IN TOTAL RNA 5HMC MODIFICATION. TET2 INTERACTED WITH THE KEY NON-SENSE-MEDIATED MRNA DECAY (NMD) FACTOR UPF1, REGULATED THE STABILITY OF STRESS-RELATED GENES SUCH AS UNC5B MRNA, AND MIGHT THEREBY AFFECT NEURODEVELOPMENT. DISCUSSION: IN SUMMARY, THIS STUDY REVEALED THAT TET2-MEDIATED RNA 5HMC MODIFICATION IS INVOLVED IN STRESS-RELATED MRNA STABILITY REGULATION AND MAY SERVE AS A POTENTIAL THERAPEUTIC TARGET FOR CHRONIC STRESS-RELATED DISEASES SUCH AS DEPRESSION. 2023 3 2111 62 EPIGENETIC FUNCTION OF TET FAMILY, 5-METHYLCYTOSINE, AND 5-HYDROXYMETHYLCYTOSINE IN HEMATOLOGIC MALIGNANCIES. DNA METHYLATION PLAYS SIGNIFICANT ROLES IN A VARIETY OF BIOLOGICAL AND PATHOLOGICAL PROCESSES INCLUDING MAMMALIAN DEVELOPMENT, GENOMIC IMPRINTING, RETROTRANSPOSON SILENCING, AND X-CHROMOSOME INACTIVATION. RECENT DISCOVERIES INDICATED THAT TEN-ELEVEN TRANSLOCATION (TET) FAMILY OF DIOXYGENASES CAN CONVERT 5-METHYLCYTOSINE (5-MC) INTO 5-HYDROXYMETHYLCYTOSINE (5-HMC). THE TET FAMILY INCLUDES THREE MEMBERS: TET1, TET2, AND TET3. WITH INCREASING EVIDENCE, MORE AND MORE BIOLOGICAL AND PATHOLOGICAL PROCESSES IN WHICH 5-HMC AND TET FAMILY SERVE UNPARALLELED BIOLOGICAL ROLES ARE NOTICED, FOR EXAMPLE, DNA DEMETHYLATION AND TRANSCRIPTIONAL REGULATION OF DIFFERENT TARGET GENES, WHICH ARE INVOLVED IN MANY HUMAN DISEASES, ESPECIALLY HEMATOLOGIC MALIGNANCIES, RESEMBLING CHRONIC MYELOMONOCYTIC LEUKEMIA, MYELODYSPLASTIC SYNDROMES, AND SO ON. IN THIS REVIEW, WE FOCUS ON THE DIVERSE FUNCTIONS OF TET FAMILY AND THE NOVEL EPIGENETIC MARKS, 5-MC AND 5-HMC, IN HEMATOLOGIC MALIGNANCIES. THIS REVIEW WILL PROVIDE VALUABLE INSIGHTS INTO THE POTENTIAL TARGETS OF HEMATOLOGIC MALIGNANCIES. FURTHER UNDERSTANDING OF THE NORMAL AND PATHOLOGICAL FUNCTIONS OF TET FAMILY MAY PROVIDE NEW METHODS TO DEVELOP NOVEL EPIGENETIC THERAPIES FOR TREATING HEMATOLOGIC MALIGNANCIES. 2019 4 394 30 AN UPDATE IN EPIGENETICS IN METABOLIC-ASSOCIATED FATTY LIVER DISEASE. METABOLIC-ASSOCIATED FATTY LIVER DISEASE (MAFLD) IS CHARACTERIZED BY HEPATIC STEATOSIS ACCOMPANIED BY ONE OF THREE FEATURES: OVERWEIGHT OR OBESITY, T2DM, OR LEAN OR NORMAL WEIGHT WITH EVIDENCE OF METABOLIC DYSREGULATION. IT IS DISTINGUISHED BY EXCESSIVE FAT ACCUMULATION IN HEPATOCYTES, AND A DECREASE IN THE LIVER'S ABILITY TO OXIDIZE FATS, THE ACCUMULATION OF ECTOPIC FAT, AND THE ACTIVATION OF PROINFLAMMATORY PATHWAYS. CHRONIC DAMAGE WILL KEEP THIS PATHOPHYSIOLOGIC CYCLE ACTIVE CAUSING PROGRESSION FROM HEPATIC STEATOSIS TO CIRRHOSIS AND EVENTUALLY, HEPATOCARCINOMA. EPIGENETICS AFFECTING GENE EXPRESSION WITHOUT ALTERING DNA SEQUENCE ALLOWS US TO STUDY MAFLD PATHOPHYSIOLOGY FROM A DIFFERENT PERSPECTIVE, IN WHICH DNA METHYLATION PROCESSES, HISTONE MODIFICATIONS, AND MIRNAS EXPRESSION HAVE BEEN CLOSELY ASSOCIATED WITH MAFLD PROGRESSION. HOWEVER, THESE CONSIDERATIONS ALSO FACED US WITH THE CIRCUMSTANCE THAT MODIFYING THOSE EPIGENETICS PATTERNS MIGHT LEAD TO MAFLD REGRESSION. CURRENTLY, EPIGENETICS IS AN AREA OF GREAT INTEREST BECAUSE IT COULD PROVIDE NEW INSIGHTS IN THERAPEUTIC TARGETS AND NON-INVASIVE BIOMARKERS. THIS REVIEW COMPRISES AN UPDATE ON THE ROLE OF EPIGENETIC PATTERNS, AS WELL AS INNOVATIVE THERAPEUTIC TARGETS AND BIOMARKERS IN MAFLD. 2021 5 5973 31 TET-CATALYZED 5-HYDROXYMETHYLATION PRECEDES HNF4A PROMOTER CHOICE DURING DIFFERENTIATION OF BIPOTENT LIVER PROGENITORS. UNDERSTANDING THE PROCESSES THAT GOVERN LIVER PROGENITOR CELL DIFFERENTIATION HAS IMPORTANT IMPLICATIONS FOR THE DESIGN OF STRATEGIES TARGETING CHRONIC LIVER DISEASES, WHEREBY REGENERATION OF LIVER TISSUE IS CRITICAL. ALTHOUGH DNA METHYLATION (5MC) AND HYDROXYMETHYLATION (5HMC) ARE HIGHLY DYNAMIC DURING EARLY EMBRYONIC DEVELOPMENT, LESS IS KNOWN ABOUT THEIR ROLES AT LATER STAGES OF DIFFERENTIATION. USING AN IN VITRO MODEL OF HEPATOCYTE DIFFERENTIATION, WE SHOW HERE THAT 5HMC PRECEDES THE EXPRESSION OF PROMOTER 1 (P1)-DEPENDENT ISOFORMS OF HNF4A, A MASTER TRANSCRIPTION FACTOR OF HEPATOCYTE IDENTITY. 5HMC AND HNF4A EXPRESSION FROM P1 ARE DEPENDENT ON TEN-ELEVEN TRANSLOCATION (TET) DIOXYGENASES. IN TURN, THE LIVER PIONEER FACTOR FOXA2 IS NECESSARY FOR TET1 BINDING TO THE P1 LOCUS. BOTH FOXA2 AND TETS ARE REQUIRED FOR THE 5HMC-RELATED SWITCH IN HNF4A EXPRESSION. THE EPIGENETIC EVENT IDENTIFIED HERE MAY BE A KEY STEP FOR THE ESTABLISHMENT OF THE HEPATOCYTE PROGRAM BY HNF4A. 2017 6 3729 32 INHIBITION OF TET1 PREVENTS THE DEVELOPMENT OF OSTEOARTHRITIS AND REVEALS THE 5HMC LANDSCAPE THAT ORCHESTRATES PATHOGENESIS. OSTEOARTHRITIS (OA) IS A DEGENERATIVE DISEASE OF THE JOINT, WHICH RESULTS IN PAIN, LOSS OF MOBILITY, AND, EVENTUALLY, JOINT REPLACEMENT. CURRENTLY, NO DISEASE-MODIFYING DRUGS EXIST, PARTLY BECAUSE OF THE MULTIPLE LEVELS AT WHICH CARTILAGE HOMEOSTASIS IS DISRUPTED. RECENT STUDIES HAVE HIGHLIGHTED THE IMPORTANCE OF EPIGENETIC DYSREGULATION IN OA, SPARKING INTEREST IN THE EPIGENETIC MODULATION FOR THIS DISEASE. IN OUR PREVIOUS WORK, WE CHARACTERIZED A FIVEFOLD INCREASE IN CYTOSINE HYDROXYMETHYLATION (5HMC), AN OXIDIZED DERIVATIVE OF CYTOSINE METHYLATION (5MC) ASSOCIATED WITH GENE ACTIVATION, ACCUMULATING AT OA-ASSOCIATED GENES. TO TEST THE ROLE OF 5HMC IN OA, HERE, WE USED A MOUSE MODEL OF SURGICALLY INDUCED OA AND FOUND THAT OA ONSET WAS ACCOMPANIED BY A GAIN OF ~40,000 DIFFERENTIALLY HYDROXYMETHYLATED SITES BEFORE THE NOTABLE HISTOLOGICAL APPEARANCE OF DISEASE. WE DEMONSTRATED THAT TEN-ELEVEN-TRANSLOCATION ENZYME 1 (TET1) MEDIATES THE 5HMC DEPOSITION BECAUSE 98% OF SITES ENRICHED FOR 5HMC IN OA WERE LOST IN TET1(-/-) MICE. LOSS OF TET1-MEDIATED 5HMC PROTECTED THE TET1(-/-) MICE FROM OA DEVELOPMENT, INCLUDING DEGENERATION OF THE CARTILAGE SURFACE AND OSTEOPHYTE FORMATION, BY DIRECTLY PREVENTING THE ACTIVATION OF MULTIPLE OA PATHWAYS. LOSS OF TET1 IN HUMAN OA CHONDROCYTES REDUCED THE EXPRESSION OF THE MATRIX METALLOPROTEINASES MMP3 AND MMP13 AND MULTIPLE INFLAMMATORY CYTOKINES. INTRA-ARTICULAR INJECTIONS OF A DIOXYGENASES INHIBITOR, 2-HYDROXYGLUTARATE, ON MICE AFTER SURGICAL INDUCTION OF OA STALLED DISEASE PROGRESSION. TREATMENT OF HUMAN OA CHONDROCYTES WITH THE SAME INHIBITOR ALSO PHENOCOPIED TET1 LOSS. COLLECTIVELY, THESE DATA DEMONSTRATE THAT TET1-MEDIATED 5HMC DEPOSITION REGULATES MULTIPLE OA PATHWAYS AND CAN BE MODULATED FOR THERAPEUTIC INTERVENTION. 2020 7 3433 35 HYDROXYMETHYLATION OF MICRORNA-365-3P REGULATES NOCICEPTIVE BEHAVIORS VIA KCNH2. DNA 5-HYDROXYLMETHYLCYTOSINE (5HMC) CATALYZED BY TEN-ELEVEN TRANSLOCATION METHYLCYTOSINE DIOXYGENASE (TET) OCCURS ABUNDANTLY IN NEURONS OF MAMMALS. HOWEVER, THE IN VIVO CAUSAL LINK BETWEEN TET DYSREGULATION AND NOCICEPTIVE MODULATION HAS NOT BEEN ESTABLISHED. HERE, WE FOUND THAT SPINAL TET1 AND TET3 WERE SIGNIFICANTLY INCREASED IN THE MODEL OF FORMALIN-INDUCED ACUTE INFLAMMATORY PAIN, WHICH WAS ACCOMPANIED WITH THE AUGMENT OF GENOME-WIDE 5HMC CONTENT IN SPINAL CORD. KNOCKDOWN OF SPINAL TET1 OR TET3 ALLEVIATED THE FORMALIN-INDUCED NOCICEPTIVE BEHAVIOR AND OVEREXPRESSION OF SPINAL TET1 OR TET3 IN NAIVE MICE PRODUCED PAIN-LIKE BEHAVIOR AS EVIDENCED BY DECREASED THERMAL PAIN THRESHOLD. FURTHERMORE, WE FOUND THAT TET1 OR TET3 REGULATED THE NOCICEPTIVE BEHAVIOR BY TARGETING MICRORNA-365-3P (MIR-365-3P). FORMALIN INCREASED 5HMC IN THE MIR-365-3P PROMOTER, WHICH WAS INHIBITED BY KNOCKDOWN OF TET1 OR TET3 AND MIMICKED BY OVEREXPRESSION OF TET1 OR TET3 IN NAIVE MICE. NOCICEPTIVE BEHAVIOR INDUCED BY FORMALIN OR OVEREXPRESSION OF SPINAL TET1 OR TET3 COULD BE PREVENTED BY DOWNREGULATION OF MIR-365-3P, AND MIMICKED BY OVEREXPRESSION OF SPINAL MIR-365-3P. FINALLY, WE DEMONSTRATED THAT A POTASSIUM CHANNEL, VOLTAGE-GATED EAG-RELATED SUBFAMILY H MEMBER 2 (KCNH2), VALIDATED AS A TARGET OF MIR-365-3P, PLAYED A CRITICAL ROLE IN NOCICEPTIVE MODULATION BY SPINAL TET OR MIR-365-3P. TOGETHER, WE CONCLUDED THAT TET-MEDIATED HYDROXYMETHYLATION OF MIR-365-3P REGULATES NOCICEPTIVE BEHAVIOR VIA KCNH2. SIGNIFICANCE STATEMENT: MOUNTING EVIDENCE INDICATES THAT EPIGENETIC MODIFICATIONS IN THE NOCICEPTIVE PATHWAY CONTRIBUTE TO PAIN PROCESSES AND ANALGESIA RESPONSE. HERE, WE FOUND THAT THE INCREASE OF 5HMC CONTENT MEDIATED BY TET1 OR TET3 IN MIR-365-3P PROMOTER IN THE SPINAL CORD IS INVOLVED IN NOCICEPTIVE MODULATION THROUGH TARGETING A POTASSIUM CHANNEL, KCNH2. OUR STUDY REVEALS A NEW EPIGENETIC MECHANISM UNDERLYING NOCICEPTIVE INFORMATION PROCESSING, WHICH MAY BE A NOVEL TARGET FOR DEVELOPMENT OF ANTINOCICEPTIVE DRUGS. 2016 8 5965 43 TEN-ELEVEN-TRANSLOCATION 2 (TET2) NEGATIVELY REGULATES HOMEOSTASIS AND DIFFERENTIATION OF HEMATOPOIETIC STEM CELLS IN MICE. THE TEN-ELEVEN-TRANSLOCATION 2 (TET2) GENE ENCODES A MEMBER OF TET FAMILY ENZYMES THAT ALTERS THE EPIGENETIC STATUS OF DNA BY OXIDIZING 5-METHYLCYTOSINE TO 5-HYDROXYMETHYLCYTOSINE (5HMC). SOMATIC LOSS-OF-FUNCTION MUTATIONS OF TET2 ARE FREQUENTLY OBSERVED IN PATIENTS WITH DIVERSE MYELOID MALIGNANCIES, INCLUDING MYELODYSPLASTIC SYNDROMES, MYELOPROLIFERATIVE NEOPLASMS, AND CHRONIC MYELOMONOCYTIC LEUKEMIA. BY ANALYZING MICE WITH TARGETED DISRUPTION OF THE TET2 CATALYTIC DOMAIN, WE SHOW HERE THAT TET2 IS A CRITICAL REGULATOR OF SELF-RENEWAL AND DIFFERENTIATION OF HEMATOPOIETIC STEM CELLS (HSCS). TET2 DEFICIENCY LED TO DECREASED GENOMIC LEVELS OF 5HMC AND AUGMENTED THE SIZE OF THE HEMATOPOIETIC STEM/PROGENITOR CELL POOL IN A CELL-AUTONOMOUS MANNER. IN COMPETITIVE TRANSPLANTATION ASSAYS, TET2-DEFICIENT HSCS WERE CAPABLE OF MULTILINEAGE RECONSTITUTION AND POSSESSED A COMPETITIVE ADVANTAGE OVER WILD-TYPE HSCS, RESULTING IN ENHANCED HEMATOPOIESIS INTO BOTH LYMPHOID AND MYELOID LINEAGES. IN VITRO, TET2 DEFICIENCY DELAYED HSC DIFFERENTIATION AND SKEWED DEVELOPMENT TOWARD THE MONOCYTE/MACROPHAGE LINEAGE. OUR DATA INDICATE THAT TET2 HAS A CRITICAL ROLE IN REGULATING THE EXPANSION AND FUNCTION OF HSCS, PRESUMABLY BY CONTROLLING 5HMC LEVELS AT GENES IMPORTANT FOR THE SELF-RENEWAL, PROLIFERATION, AND DIFFERENTIATION OF HSCS. 2011 9 21 24 5-HYDROXYMETHYLCYTOSINE (5HMC) AND TEN-ELEVEN TRANSLOCATION 1-3 (TET1-3) PROTEINS IN THE DORSAL ROOT GANGLIA OF MOUSE: EXPRESSION AND DYNAMIC REGULATION IN NEUROPATHIC PAIN. EPIGENETIC MECHANISMS ARE INCREASINGLY IMPLICATED IN CHRONIC PAIN PATHOLOGY. IN THIS STUDY, WE DEMONSTRATE THAT THE NOVEL EPIGENETIC MARK 5-HYDROXYMETHYLCYTOSINE (5HMC) IS PRESENT IN DORSAL ROOT GANGLIA (DRG) NEURONS AND GLIA, AND ITS LEVELS INCREASE FOLLOWING NERVE INJURY. FURTHERMORE, WE SHOW THAT THE 5HMC-GENERATING TEN-ELEVEN TRANSLOCATION 1-3 (TET1-3) PROTEINS ARE EXPRESSED IN A CELL-TYPE SPECIFIC MANNER IN THE DRG, WITH TET3 DISPLAYING DIFFERENTIAL UPREGULATION AFTER INJURY, SUGGESTING A POTENTIAL ROLE IN NEUROPATHIC PAIN. 2017 10 6651 23 UPDATE ON GENETICS AND EPIGENETICS IN METABOLIC ASSOCIATED FATTY LIVER DISEASE. NONALCOHOLIC FATTY LIVER DISEASE (NAFLD) IS BECOMING THE MOST FREQUENT CHRONIC LIVER DISEASE WORLDWIDE. METABOLIC (DYSFUNCTION) ASSOCIATED FATTY LIVER DISEASE (MAFLD) IS SUGGESTED TO REPLACE THE NOMENCLATURE OF NAFLD. FOR INDIVIDUALS WITH METABOLIC DYSFUNCTION, MULTIPLE NAFLD-RELATED FACTORS ALSO CONTRIBUTE TO THE DEVELOPMENT AND PROGRESSION OF MAFLD INCLUDING GENETICS AND EPIGENETICS. THE APPLICATION OF GENOME-WIDE ASSOCIATION STUDY (GWAS) AND EXOME-WIDE ASSOCIATION STUDY (EWAS) UNCOVERS SINGLE-NUCLEOTIDE POLYMORPHISMS (SNPS) IN MAFLD. IN ADDITION TO THE CLASSIC SNPS IN PNPLA3, TM6SF2, AND GCKR, SOME NEW SNPS HAVE BEEN FOUND RECENTLY TO CONTRIBUTE TO THE PATHOGENESIS OF LIVER STEATOSIS. EPIGENETIC FACTORS INVOLVING DNA METHYLATION, HISTONE MODIFICATIONS, NON-CODING RNAS REGULATIONS, AND RNA METHYLATION ALSO PLAY A CRITICAL ROLE IN MAFLD. DNA METHYLATION IS THE MOST REPORTED EPIGENETIC MODIFICATION. DEVELOPING A NON-INVASION BIOMARKER TO DISTINGUISH METABOLIC STEATOHEPATITIS (MASH) OR LIVER FIBROSIS IS ONGOING. IN THIS REVIEW, WE SUMMARIZED AND DISCUSSED THE LATEST PROGRESS IN GENETIC AND EPIGENETIC FACTORS OF NAFLD/MAFLD, IN ORDER TO PROVIDE POTENTIAL CLUES FOR MAFLD TREATMENT. 2022 11 4583 21 N6-METHYLADENINE RNA METHYLATION EPIGENETIC MODIFICATION AND KIDNEY DISEASES. RNA METHYLATION MODIFICATION IS A RAPIDLY DEVELOPING FIELD IN EPIGENETICS. N6-METHYLADENSINE (M(6)A) IS THE MOST COMMON INTERNAL MODIFICATION IN EUKARYOTIC MRNA. M(6)A GROUP REGULATES RNA SPLICING, STABILITY, TRANSLOCATION, AND TRANSLATION. ENZYMES CATALYZING THIS PROCESS WERE TERMED AS WRITERS, ERASERS, AND READERS. RECENT STUDIES HAVE FOCUSED ON EXPLORING THE ROLE OF RNA METHYLATION IN HUMAN DISEASES. RNA METHYLATION MODIFICATIONS, PARTICULARLY M(6)A, PLAY IMPORTANT ROLES IN THE PATHOGENESIS OF KIDNEY DISEASES. IN THIS REVIEW, WE PROVIDE A BRIEF DESCRIPTION OF M(6)A AND SUMMARIZE THE IMPACT OF M(6)A ON ACUTE AND CHRONIC KIDNEY DISEASE (CKD) AND POSSIBLE FUTURE STUDY DIRECTIONS FOR THIS RESEARCH. 2023 12 5981 35 TET2 PROMOTES PATHOGEN INFECTION-INDUCED MYELOPOIESIS THROUGH MRNA OXIDATION. VARIETIES OF RNA MODIFICATION FORM THE EPITRANSCRIPTOME FOR POST-TRANSCRIPTIONAL REGULATION. 5-METHYLCYTOSINE (5-MC) IS A SPARSE RNA MODIFICATION IN MESSENGER RNA (MRNA) UNDER PHYSIOLOGICAL CONDITIONS. THE FUNCTION OF RNA 5-HYDROXYMETHYLCYTOSINE (5-HMC) OXIDIZED BY TEN-ELEVEN TRANSLOCATION (TET) PROTEINS IN DROSOPHILA HAS BEEN REVEALED MORE RECENTLY. HOWEVER, THE TURNOVER AND FUNCTION OF 5-MC IN MAMMALIAN MRNA HAVE BEEN LARGELY UNKNOWN. TET2 SUPPRESSES MYELOID MALIGNANCIES MOSTLY IN AN ENZYMATIC ACTIVITY-DEPENDENT MANNER, AND IS IMPORTANT IN RESOLVING INFLAMMATORY RESPONSE IN AN ENZYMATIC ACTIVITY-INDEPENDENT WAY. MYELOPOIESIS IS A COMMON HOST IMMUNE RESPONSE IN ACUTE AND CHRONIC INFECTIONS; HOWEVER, ITS EPIGENETIC MECHANISM NEEDS TO BE IDENTIFIED. HERE WE DEMONSTRATE THAT TET2 PROMOTES INFECTION-INDUCED MYELOPOIESIS IN AN MRNA OXIDATION-DEPENDENT MANNER THROUGH ADAR1-MEDIATED REPRESSION OF SOCS3 EXPRESSION AT THE POST-TRANSCRIPTION LEVEL. TET2 PROMOTES BOTH ABDOMINAL SEPSIS-INDUCED EMERGENCY MYELOPOIESIS AND PARASITE-INDUCED MAST CELL EXPANSION THROUGH DECREASING MRNA LEVELS OF SOCS3, A KEY NEGATIVE REGULATOR OF THE JAK-STAT PATHWAY THAT IS CRITICAL FOR CYTOKINE-INDUCED MYELOPOIESIS. TET2 REPRESSES SOCS3 EXPRESSION THROUGH ADAR1, WHICH BINDS AND DESTABILIZES SOCS3 MRNA IN A RNA EDITING-INDEPENDENT MANNER. FOR THE UNDERLYING MECHANISM OF TET2 REGULATION AT THE MRNA LEVEL, TET2 MEDIATES OXIDATION OF 5-MC IN MRNA. TET2 DEFICIENCY LEADS TO THE TRANSCRIPTOME-WIDE APPEARANCE OF METHYLATED CYTOSINES, INCLUDING ONES IN THE 3' UNTRANSLATED REGION OF SOCS3, WHICH INFLUENCES DOUBLE-STRANDED RNA FORMATION FOR ADAR1 BINDING, PROBABLY THROUGH CYTOSINE METHYLATION-SPECIFIC READERS, SUCH AS RNA HELICASES. OUR STUDY REVEALS A PREVIOUSLY UNKNOWN REGULATORY ROLE OF TET2 AT THE EPITRANSCRIPTOMIC LEVEL, PROMOTING MYELOPOIESIS DURING INFECTION IN THE MAMMALIAN SYSTEM BY DECREASING 5-MCS IN MRNAS. MOREOVER, THE INHIBITORY FUNCTION OF CYTOSINE METHYLATION ON DOUBLE-STRANDED RNA FORMATION AND ADAR1 BINDING IN MRNA REVEALS ITS NEW PHYSIOLOGICAL ROLE IN THE MAMMALIAN SYSTEM. 2018 13 895 35 CHRONIC ETHANOL-MEDIATED HEPATOCYTE APOPTOSIS LINKS TO DECREASED TET1 AND 5-HYDROXYMETHYLCYTOSINE FORMATION. THE 5-HYDROXYMETHYLCYTOSINE (5HMC) IS A NEWLY IDENTIFIED EPIGENETIC MODIFICATION THOUGHT TO BE REGULATED BY THE TET FAMILY OF PROTEINS. LITTLE INFORMATION IS AVAILABLE ABOUT HOW ETHANOL CONSUMPTION MAY MODULATE 5HMC FORMATION AND ALCOHOLIC LIVER DISEASE (ALD) PROGRESSION. A RAT ALD MODEL WAS USED TO STUDY 5HMC IN RELATIONSHIP TO HEPATOCYTE APOPTOSIS. HUMAN ALD LIVER SAMPLES WERE ALSO USED TO VALIDATE THESE FINDINGS. IT WAS FOUND THAT CHRONIC ETHANOL FEEDING SIGNIFICANTLY REDUCED 5HMC FORMATION IN A RAT ALD MODEL. THERE WERE NO SIGNIFICANT CHANGES IN TET2 AND TET3 BETWEEN THE CONTROL- AND ETHANOL-FED ANIMALS. IN CONTRAST, METHYLCYTOSINE DIOXYGENASE TET1 (TET1) EXPRESSION WAS SUBSTANTIALLY REDUCED IN THE ETHANOL-FED RATS AND WAS ACCOMPANIED BY INCREASED HEPATOCYTE APOPTOSIS. SIMILARLY, KNOCKDOWN OF TET1 IN HUMAN HEPATOCYTE-LIKE CELLS ALSO SIGNIFICANTLY PROMOTED APOPTOSIS. DOWN-REGULATION OF TET1 RESULTED IN ELEVATED EXPRESSION OF THE DNA DAMAGE MARKER, SUGGESTING A ROLE FOR 5HMC IN HEPATOCYTE DNA DAMAGE AS WELL. MECHANISTIC STUDIES REVEALED THAT INHIBITION OF TET1 PROMOTED APOPTOTIC GENE EXPRESSION. SIMILARLY, TARGETING TET1 ACTIVITY BY REMOVING COSUBSTRATE PROMOTED APOPTOSIS AND DNA DAMAGE. FURTHERMORE, TREATMENT WITH 5-AZACITIDINE SIGNIFICANTLY MIMICS THESE EFFECTS, SUGGESTING THAT CHRONIC ETHANOL CONSUMPTION PROMOTES HEPATOCYTE APOPTOSIS AND DNA DAMAGE BY DIMINISHING TET1-MEDIATED 5HMC FORMATION AND DNA METHYLATION. IN SUMMARY, THE CURRENT STUDY PROVIDES A NOVEL MOLECULAR INSIGHT THAT TET1-MEDIATED 5HMC IS INVOLVED IN HEPATOCYTE APOPTOSIS IN ALD PROGRESSION.-JI, C., NAGAOKA, K., ZOU, J., CASULLI, S., LU, S., CAO, K. Y., ZHANG, H., IWAGAMI, Y., CARLSON, R. I., BROOKS, K., LAWRENCE, J., MUELLER, W., WANDS, J. R., HUANG, C.-K. CHRONIC ETHANOL-MEDIATED HEPATOCYTE APOPTOSIS LINKS TO DECREASED TET1 AND 5-HYDROXYMETHYLCYTOSINE FORMATION. 2019 14 5975 28 TET1 IS AN IMPORTANT TRANSCRIPTIONAL ACTIVATOR OF TNFALPHA EXPRESSION IN MACROPHAGES. ACTIVATION OF MACROPHAGES AND OVEREXPRESSION OF TNFALPHA IS ASSOCIATED WITH THE PATHOGENESIS OF CHRONIC INFLAMMATORY DISEASES. HOWEVER, THE MECHANISMS LEADING TO TNFALPHA OVEREXPRESSION ARE STILL UNKNOWN. 5-METHYLOCYTOSINE (5-MC) IS AN EPIGENETIC MODIFICATION THAT IS ASSOCIATED WITH SILENCED GENES. RECENT STUDIES SHOWED THAT IT IS CONVERTED TO 5-HYDROXYLMETHYLOCYTOSINE (5-HMC) AND REACTIVATES GENE EXPRESSION THROUGH THE ACTION OF THE FAMILY OF TEN-ELEVEN-TRANSLOCATION (TET1-3) ENZYMES. IN THIS STUDY, WE SHOW THAT 5-HMC LEVELS ARE INCREASED GLOBALLY AND SPECIFICALLY IN THE TNFALPHA PROMOTER DURING THE DIFFERENTIATION OF MONOCYTES TO MACROPHAGES. IN ADDITION, THE LEVELS OF 5-HMC ARE INCREASED UPON LPS STIMULATION OF MACROPHAGES. FURTHERMORE, CRIPSR STABLE KNOCKOUT OF TET1 DECREASES THE EXPRESSION OF TNFALPHA AND OTHER PRO-INFLAMMATORY CYTOKINES. IN CONCLUSION, WE SHOWED THAT TET1 CONTRIBUTES TO THE ACTIVATION OF MACROPHAGES POSSIBLY THROUGH REGULATION OF 5-HYDROXYMETHYLATION IN THE PROMOTER OF PRO-INFLAMMATORY CYTOKINE GENES. THE TET1 ENZYME COULD BE A PROMISING THERAPEUTIC TARGET TO INHIBIT THE PERSISTENT INFLAMMATION CAUSED BY MACROPHAGES IN CHRONIC INFLAMMATORY DISEASES. 2019 15 1720 28 DYSREGULATED N6-METHYLADENOSINE (M(6)A) PROCESSING IN HEPATOCELLULAR CARCINOMA. N6-METHYLADENOSINE (M(6)A) IS THE MOST THOROUGHLY STUDIED TYPE OF INTERNAL RNA MODIFICATION, AS THIS EPIGENETIC MODIFICATION IS THE MOST ABUNDANT IN EUKARYOTIC RNAS TO DATE. THIS MODIFICATION OCCURS IN VARIOUS TYPES OF RNAS AND PLAYS SIGNIFICANT ROLES IN DOMINANT RNA-RELATED PROCESSES, SUCH AS TRANSLATION, SPLICING, EXPORT AND DEGRADATION. THESE PROCESSES ARE CATALYZED BY THREE TYPES OF PROMINENT ENZYMES: WRITERS, ERASERS AND READERS. INCREASING EVIDENCE HAS SHOWN THAT M(6)A MODIFICATION IS VITAL FOR THE REGULATION OF GENE EXPRESSION, CARCINOGENESIS, TUMOR PROGRESSION AND OTHER ABNORMAL CHANGES, AND RECENT STUDIES HAVE SHOWN THAT M(6)A IS IMPORTANT IN THE DEVELOPMENT OF HEPATOCELLULAR CARCINOMA (HCC). HEREIN, WE SUMMARIZE THE NATURE AND REGULATORY MECHANISMS OF M(6)A MODIFICATION, INCLUDING ITS ROLE IN THE PATHOGENESIS OF HCC AND RELATED CHRONIC LIVER DISEASES. WE ALSO HIGHLIGHT THE CLINICAL SIGNIFICANCE AND FUTURE STRATEGIES INVOLVING RNA M(6)A MODIFICATIONS IN HCC. 2021 16 469 25 ARID1A LOSS DRIVES NONALCOHOLIC STEATOHEPATITIS IN MICE THROUGH EPIGENETIC DYSREGULATION OF HEPATIC LIPOGENESIS AND FATTY ACID OXIDATION. NONALCOHOLIC STEATOHEPATITIS (NASH) IS A RAPIDLY GROWING CAUSE OF CHRONIC LIVER DAMAGE, CIRRHOSIS, AND HEPATOCELLULAR CARCINOMA. HOW FATTY LIVER PATHOGENESIS IS SUBJECT TO EPIGENETIC REGULATION IS UNKNOWN. WE HYPOTHESIZED THAT CHROMATIN REMODELING IS IMPORTANT FOR THE PATHOGENESIS OF FATTY LIVER DISEASE. AT-RICH INTERACTIVE DOMAIN-CONTAINING PROTEIN 1A (ARID1A), A DNA-BINDING COMPONENT OF THE SWITCH/SUCROSE NONFERMENTABLE ADENOSINE TRIPHOSPHATE-DEPENDENT CHROMATIN-REMODELING COMPLEX, CONTRIBUTES TO NUCLEOSOME REPOSITIONING AND ACCESS BY TRANSCRIPTIONAL REGULATORS. LIVER-SPECIFIC DELETION OF ARID1A (ARID1A LIVER KNOCKOUT [LKO]) CAUSED THE DEVELOPMENT OF AGE-DEPENDENT FATTY LIVER DISEASE IN MICE. TRANSCRIPTOME ANALYSIS REVEALED UP-REGULATION OF LIPOGENESIS AND DOWN-REGULATION OF FATTY ACID OXIDATION GENES. AS EVIDENCE OF DIRECT REGULATION, ARID1A DEMONSTRATED DIRECT BINDING TO THE PROMOTERS OF MANY OF THESE DIFFERENTIALLY REGULATED GENES. ADDITIONALLY, ARID1A LKO MICE WERE MORE SUSCEPTIBLE TO HIGH-FAT DIET-INDUCED LIVER STEATOSIS AND FIBROSIS. WE DELETED PTEN IN COMBINATION WITH ARID1A TO SYNERGISTICALLY DRIVE FATTY LIVER PROGRESSION. INHIBITION OF LIPOGENESIS USING CAT-2003, A POTENT STEROL REGULATORY ELEMENT-BINDING PROTEIN INHIBITOR, MEDIATED IMPROVEMENTS IN MARKERS OF FATTY LIVER DISEASE PROGRESSION IN THIS ARID1A/PTEN DOUBLE KNOCKOUT MODEL. CONCLUSION: ARID1A PLAYS A ROLE IN THE EPIGENETIC REGULATION OF HEPATIC LIPID HOMEOSTASIS, AND ITS SUPPRESSION CONTRIBUTES TO FATTY LIVER PATHOGENESIS. COMBINED ARID1A AND PTEN DELETION SHOWS ACCELERATED FATTY LIVER DISEASE PROGRESSION AND IS A USEFUL MOUSE MODEL FOR STUDYING THERAPEUTIC STRATEGIES FOR NASH. 2019 17 5825 31 STRESS MODULATES AHI1-DEPENDENT NUCLEAR LOCALIZATION OF TEN-ELEVEN TRANSLOCATION PROTEIN 2. MAJOR DEPRESSION DISORDER IS ONE OF THE MOST COMMON PSYCHIATRIC DISEASES. RECENT EVIDENCE SUPPORTS THAT ENVIRONMENTAL STRESS AFFECTS GENE EXPRESSION AND PROMOTES THE PATHOLOGICAL PROCESS OF DEPRESSION THROUGH EPIGENETIC MECHANISMS. THREE TEN-ELEVEN TRANSLOCATION (TET) ENZYMES ARE EPIGENETIC REGULATORS OF GENE EXPRESSION THAT PROMOTE 5-HYDROXYMETHYLCYTOSINE (5HMC) MODIFICATION OF GENES. HERE, WE SHOW THAT THE LOSS OF TET2 CAN INDUCE DEPRESSION-LIKE PHENOTYPES IN MICE. PARADOXICALLY, USING THE PARADIGMS OF CHRONIC STRESS, SUCH AS CHRONIC MILD STRESS AND CHRONIC SOCIAL DEFEAT STRESS, WE FOUND THAT DEPRESSIVE BEHAVIORS WERE ASSOCIATED WITH INCREASED TET2 EXPRESSION BUT DECREASED GLOBAL 5HMC LEVEL IN HIPPOCAMPUS. WE EXAMINED THE GENOME-WIDE 5HMC PROFILE IN THE HIPPOCAMPUS OF TET2 KNOCKOUT MICE AND IDENTIFIED 651 DYNAMICALLY HYDROXYMETHYLATED REGIONS, SOME OF WHICH OVERLAPPED WITH KNOWN DEPRESSION-ASSOCIATED LOCI. WE FURTHER SHOWED THAT CHRONIC STRESS COULD INDUCE THE ABNORMAL NUCLEAR TRANSLOCATION OF TET2 PROTEIN FROM CYTOSOL. THROUGH TET2 IMMUNOPRECIPITATION AND MASS SPECTRUM ANALYSES, WE IDENTIFIED A CELLULAR TRAFFICKING PROTEIN, ABELSON HELPER INTEGRATION SITE-1 (AHI1), WHICH COULD INTERACT WITH TET2 PROTEIN. AHI1 KNOCKOUT OR KNOCKDOWN CAUSED THE ACCUMULATION OF TET2 IN CYTOSOL. THE REDUCTION OF AHI1 PROTEIN UNDER CHRONIC STRESS EXPLAINED THE ABNORMAL AHI1-DEPENDENT NUCLEAR TRANSLOCATION OF TET2. THESE FINDINGS TOGETHER PROVIDE THE EVIDENCE FOR A CRITICAL ROLE OF MODULATING TET2 NUCLEAR TRANSLOCATION IN REGULATING STRESS RESPONSE. 2021 18 1021 26 CIRCULAR RNA AS AN EPIGENETIC REGULATOR IN CHRONIC LIVER DISEASES. CIRCULAR RNA (CIRCRNA) IS A TYPE OF NON-CODING RNA CHARACTERIZED BY A COVALENTLY CLOSED CONTINUOUS LOOP. CIRCRNA IS GENERATED BY PRE-MRNA THROUGH BACK-SPLICING AND IS PROBABLY CLEARED UP BY EXTRACELLULAR VESICLES. CIRCRNAS PLAY A PIVOTAL ROLE IN THE EPIGENETIC REGULATION OF GENE EXPRESSION AT TRANSCRIPTIONAL AND POST-TRANSCRIPTIONAL LEVELS. RECENTLY, CIRCRNAS HAVE BEEN DEMONSTRATED TO BE INVOLVED IN THE REGULATION OF LIVER HOMEOSTASIS AND DISEASES. HOWEVER, THE EPIGENETIC ROLE AND UNDERLYING MECHANISMS OF CIRCRNAS IN CHRONIC LIVER DISEASES REMAIN UNCLEAR. THIS REVIEW DISCUSSED THE ROLE OF CIRCRNAS IN NON-NEOPLASTIC CHRONIC LIVER DISEASES, INCLUDING ALCOHOLIC LIVER DISEASE (ALD), METABOLIC-ASSOCIATED FATTY LIVER DISEASE (MAFLD), VIRAL HEPATITIS, LIVER INJURY AND REGENERATION, LIVER CIRRHOSIS, AND AUTOIMMUNE LIVER DISEASE. THE REVIEW ALSO HIGHLIGHTED THAT FURTHER EFFORTS ARE URGENTLY NEEDED TO DEVELOP CIRCRNAS AS NOVEL DIAGNOSTICS AND THERAPEUTICS FOR CHRONIC LIVER DISEASES. 2021 19 5983 44 TET2 RESTRAINS INFLAMMATORY GENE EXPRESSION IN MACROPHAGES. TET METHYLCYTOSINE DIOXYGENASE 2 (TET2) IS ONE OF THE EARLIEST AND MOST FREQUENTLY MUTATED GENES IN CLONAL HEMATOPOIESIS OF INDETERMINATE POTENTIAL (CHIP) AND MYELOID CANCERS, INCLUDING MYELODYSPLASTIC SYNDROMES (MDS) AND CHRONIC MYELOMONOCYTIC LEUKEMIA (CMML). TET2 CATALYZES THE OXIDATION OF 5-METHYLCYTOSINE TO 5-HYDROXYMETHYLCYTOSINE, LEADING TO DNA DEMETHYLATION, AND ALSO AFFECTS TRANSCRIPTION BY RECRUITING HISTONE MODIFIERS. INACTIVATING TET2 MUTATIONS CAUSE EPIGENETIC DYSREGULATION, CLONAL HEMATOPOIETIC STEM CELL (HSC) DOMINANCE, AND MONOCYTIC LINEAGE SKEWING. HERE, WE FOUND THAT TET2 WAS THE MOST HIGHLY EXPRESSED TET ENZYME IN MURINE MACROPHAGE (MPHI) DIFFERENTIATION. TET2 TRANSCRIPTION WAS FURTHER INDUCED BY LIPOPOLYSACCHARIDE (LPS), BUT NOT INTERLEUKIN (IL)-4, STIMULATION, POTENTIALLY IN A NUCLEAR FACTOR KAPPABETA-DEPENDENT MANNER. TET2 LOSS DID NOT AFFECT EARLY LPS GENE RESPONSES IN VITRO, BUT INCREASED IL-1B, IL-6, AND ARGINASE 1 (ARG1) MRNA EXPRESSION AT LATER STAGES OF STIMULATION IN BONE-MARROW-DERIVED MPHIS (BMMPHIS). TET2-DEFICIENT PERITONEAL MPHIS, HOWEVER, DEMONSTRATED PROFOUND, CONSTITUTIVE EXPRESSION OF LPS-INDUCED GENES ASSOCIATED WITH AN INFLAMMATORY STATE IN VIVO. IN CONTRAST, TET2 DEFICIENCY DID NOT AFFECT ALTERNATIVE MPHI GENE EXPRESSION SIGNIFICANTLY IN RESPONSE TO IL-4. THESE RESULTS SUGGESTED IMPAIRED RESOLUTION OF INFLAMMATION IN THE ABSENCE OF TET2 BOTH IN VITRO AND IN VIVO. FOR THE FIRST TIME, WE ALSO DETECTED TET2 MUTATIONS IN BMMPHIS FROM MDS AND CMML PATIENTS AND ASSAYED THEIR EFFECTS ON LPS RESPONSES, INCLUDING THEIR POTENTIAL INFLUENCE ON HUMAN IL-6 EXPRESSION. OUR RESULTS SHOW THAT TET2 RESTRAINS INFLAMMATION IN MURINE MPHIS AND MICE, RAISING THE POSSIBILITY THAT LOSS OF TET2 FUNCTION IN MPHIS MAY ALTER THE IMMUNE ENVIRONMENT IN THE LARGE ELDERLY POPULATION WITH TET2-MUTANT CHIP AND IN TET2-MUTANT MYELOID CANCER PATIENTS. 2017 20 3819 27 INTRINSIC MUTAGENIC PROPERTIES OF 5-CHLOROCYTOSINE: A MECHANISTIC CONNECTION BETWEEN CHRONIC INFLAMMATION AND CANCER. DURING CHRONIC INFLAMMATION, NEUTROPHIL-SECRETED HYPOCHLOROUS ACID CAN DAMAGE NEARBY CELLS INDUCING THE GENOMIC ACCUMULATION OF 5-CHLOROCYTOSINE (5CLC), A KNOWN INFLAMMATION BIOMARKER. ALTHOUGH 5CLC HAS BEEN SHOWN TO PROMOTE EPIGENETIC CHANGES, IT HAS BEEN UNKNOWN HERETOFORE IF 5CLC DIRECTLY PERPETRATES A MUTAGENIC OUTCOME WITHIN THE CELL. THE PRESENT WORK SHOWS THAT 5CLC IS INTRINSICALLY MUTAGENIC, BOTH IN VITRO AND, AT A LEVEL OF A SINGLE MOLECULE PER CELL, IN VIVO. USING BIOCHEMICAL AND GENETIC APPROACHES, WE HAVE QUANTIFIED THE MUTAGENIC AND TOXIC PROPERTIES OF 5CLC, SHOWING THAT THIS LESION CAUSED C-->T TRANSITIONS AT FREQUENCIES RANGING FROM 3-9% DEPENDING ON THE POLYMERASE TRAVERSING THE LESION. X-RAY CRYSTALLOGRAPHIC STUDIES PROVIDED A MOLECULAR BASIS FOR THE MUTAGENICITY OF 5CLC; A SNAPSHOT OF HUMAN POLYMERASE BETA REPLICATING ACROSS A PRIMED 5CLC-CONTAINING TEMPLATE UNCOVERED 5CLC ENGAGED IN A NASCENT BASE PAIR WITH AN INCOMING DATP ANALOG. ACCOMMODATION OF THE CHLORINE SUBSTITUENT IN THE TEMPLATE MAJOR GROOVE ENABLED A UNIQUE INTERACTION BETWEEN 5CLC AND THE INCOMING DATP, WHICH WOULD FACILITATE MUTAGENIC LESION BYPASS. THE TYPE OF MUTATION INDUCED BY 5CLC, THE C-->T TRANSITION, HAS BEEN PREVIOUSLY SHOWN TO OCCUR IN SUBSTANTIAL AMOUNTS BOTH IN TISSUES UNDER INFLAMMATORY STRESS AND IN THE GENOMES OF MANY INFLAMMATION-ASSOCIATED CANCERS. IN FACT, MANY SEQUENCE-SPECIFIC MUTATIONAL SIGNATURES UNCOVERED IN SEQUENCED CANCER GENOMES FEATURE C-->T MUTATIONS. THEREFORE, THE MUTAGENIC ABILITY OF 5CLC DOCUMENTED IN THE PRESENT STUDY MAY CONSTITUTE A DIRECT FUNCTIONAL LINK BETWEEN CHRONIC INFLAMMATION AND THE GENETIC CHANGES THAT ENABLE AND PROMOTE MALIGNANT TRANSFORMATION. 2015