1 3185 102 HBC BINDS TO THE CPG ISLANDS OF HBV CCCDNA AND PROMOTES AN EPIGENETIC PERMISSIVE STATE. HBV COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) IS THE TEMPLATE FOR THE TRANSCRIPTION OF HBV. HBV CORE PROTEIN (HBC) IS A MAIN COMPONENT OF THE HBV CCCDNA MINICHROMOSOME. HOWEVER, THE FUNCTION OF HBC IN CCCDNA IS NOT FULLY UNDERSTOOD. IN LIGHT OF RECENT FINDINGS THAT HBV CCCDNA MAY BE REGULATED EPIGENETICALLY, WE ANALYZED THE BINDING OF HBC TO CCCDNA AND THE IMPACT OF HBC ON CCCDNA EPIGENETIC PROFILE IN THE LIVER BIOPSY SAMPLES OF 22 PATIENTS WITH CHRONIC HEPATITIS B (CHB). WE FOUND THAT HBC BINDING TO HBV CCCDNA OCCURRED PREFERENTIALLY AT CPG ISLAND 2, AN IMPORTANT REGION FOR THE REGULATION OF HBV TRANSCRIPTION. FURTHERMORE, THE RELATIVE ABUNDANCES OF HBC BINDING TO CPG ISLAND 2 WERE POSITIVELY CORRELATED WITH THE RATIOS OF RELAXED CIRCULAR DNA TO CCCDNA AND THE LEVELS OF SERUM HBV DNA IN THOSE PATIENTS. INTERESTINGLY, THE RELATIVE ABUNDANCES OF HBC BINDING TO CPG ISLAND 2 WERE ASSOCIATED WITH THE BINDING OF CREB BINDING PROTEIN (CBP) AND WITH HYPOMETHYLATION IN CPG ISLAND 2 OF HBV CCCDNA MINICHROMOSOMES. HOWEVER, RELATIVELY HIGHER AMOUNTS OF HBC BINDING TO CPG ISLAND 2 OF CCCDNA WERE ACCOMPANIED BY LOWER AMOUNTS OF HDAC1 BINDING. MULTIVARIATE ANALYSIS REVEALED THAT THE ABUNDANCES OF HBC BINDING TO CPG ISLAND 2 OF CCCDNA AND POSITIVE HBEAG WERE INDEPENDENT FACTORS ASSOCIATED WITH THE REPLICATION OF HBV (P = 0.001 FOR BOTH). APPARENTLY, HBC IS A POSITIVE REGULATOR OF HBV TRANSCRIPTION AND REPLICATION, MAINTAINING THE PERMISSIVE EPIGENETIC STATE IN THE CRITICAL REGION OF THE HBV CCCDNA MINICHROMOSOMES. 2011 2 94 29 A PLEIOTROPIC ROLE OF THE HEPATITIS B VIRUS CORE PROTEIN IN HEPATOCARCINOGENESIS. CHRONIC HEPATITIS B VIRUS (HBV) INFECTION IS ONE OF THE MOST COMMON FACTORS ASSOCIATED WITH HEPATOCELLULAR CARCINOMA (HCC), WHICH IS THE SIXTH MOST PREVALENT CANCER AMONG ALL CANCERS WORLDWIDE. HOWEVER, THE PATHOGENESIS OF HBV-MEDIATED HEPATOCARCINOGENESIS IS UNCLEAR. EVIDENCE CURRENTLY AVAILABLE SUGGESTS THAT THE HBV CORE PROTEIN (HBC) PLAYS A POTENTIAL ROLE IN THE DEVELOPMENT OF HCC, SUCH AS THE HBV X PROTEIN. THE CORE PROTEIN, WHICH IS THE STRUCTURAL COMPONENT OF THE VIRAL NUCLEOCAPSID, CONTRIBUTES TO ALMOST EVERY STAGE OF THE HBV LIFE CYCLE AND OCCUPIES DIVERSE ROLES IN HBV REPLICATION AND PATHOGENESIS. RECENT STUDIES HAVE SHOWN THAT HBC WAS ABLE TO DISRUPT VARIOUS PATHWAYS INVOLVED IN LIVER CARCINOGENESIS: THE SIGNALING PATHWAYS IMPLICATED IN MIGRATION AND PROLIFERATION OF HEPATOMA CELLS, APOPTOSIS PATHWAYS, AND CELL METABOLIC PATHWAYS INDUCING THE DEVELOPMENT OF HCC; AND THE IMMUNE SYSTEM, THROUGH THE EXPRESSION AND PRODUCTION OF PROINFLAMMATORY CYTOKINES. IN ADDITION, HBC CAN MODULATE NORMAL FUNCTIONS OF HEPATOCYTES THROUGH DISRUPTING HUMAN HOST GENE EXPRESSION BY BINDING TO PROMOTER REGIONS. THIS HBV PROTEIN ALSO PROMOTES HCC METASTASIS THROUGH EPIGENETIC ALTERATIONS, SUCH AS MICRO-RNA. THIS REVIEW FOCUSES ON THE MOLECULAR PATHOGENESIS OF THE HBC PROTEIN IN HBV-INDUCED HCC. 2021 3 5689 34 SILENCING HEPATITIS B VIRUS COVALENTLY CLOSED CIRCULAR DNA: THE POTENTIAL OF AN EPIGENETIC THERAPY APPROACH. GLOBAL PROPHYLACTIC VACCINATION PROGRAMMES HAVE HELPED TO CURB NEW HEPATITIS B VIRUS (HBV) INFECTIONS. HOWEVER, IT IS ESTIMATED THAT NEARLY 300 MILLION PEOPLE ARE CHRONICALLY INFECTED AND HAVE A HIGH RISK OF DEVELOPING HEPATOCELLULAR CARCINOMA. AS SUCH, HBV REMAINS A SERIOUS HEALTH PRIORITY AND THE DEVELOPMENT OF NOVEL CURATIVE THERAPEUTICS IS URGENTLY NEEDED. CHRONIC HBV INFECTION HAS BEEN ATTRIBUTED TO THE PERSISTENCE OF THE COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) WHICH ESTABLISHES ITSELF AS A MINICHROMOSOME IN THE NUCLEUS OF HEPATOCYTES. AS THE VIRAL TRANSCRIPTION INTERMEDIATE, THE CCCDNA IS RESPONSIBLE FOR PRODUCING NEW VIRIONS AND PERPETUATING INFECTION. HBV IS DEPENDENT ON VARIOUS HOST FACTORS FOR CCCDNA FORMATION AND THE MINICHROMOSOME IS AMENABLE TO EPIGENETIC MODIFICATIONS. TWO HBV PROTEINS, X (HBX) AND CORE (HBC) PROMOTE VIRAL REPLICATION BY MODULATING THE CCCDNA EPIGENOME AND REGULATING HOST CELL RESPONSES. THIS INCLUDES VIRAL AND HOST GENE EXPRESSION, CHROMATIN REMODELING, DNA METHYLATION, THE ANTIVIRAL IMMUNE RESPONSE, APOPTOSIS, AND UBIQUITINATION. ELIMINATION OF THE CCCDNA MINICHROMOSOME WOULD RESULT IN A STERILIZING CURE; HOWEVER, THIS MAY BE DIFFICULT TO ACHIEVE. EPIGENETIC THERAPIES COULD PERMANENTLY SILENCE THE CCCDNA MINICHROMOSOME AND PROMOTE A FUNCTIONAL CURE. THIS REVIEW EXPLORES THE CCCDNA EPIGENOME, HOW HOST AND VIRAL FACTORS INFLUENCE TRANSCRIPTION, AND THE RECENT EPIGENETIC THERAPIES AND EPIGENOME ENGINEERING APPROACHES THAT HAVE BEEN DESCRIBED. 2021 4 3186 32 HBV COVALENTLY CLOSED CIRCULAR DNA MINICHROMOSOMES IN DISTINCT EPIGENETIC TRANSCRIPTIONAL STATES DIFFER IN THEIR VULNERABILITY TO DAMAGE. BACKGROUND AND AIMS: HBV COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) IS A MAJOR OBSTACLE FOR A CURE OF CHRONIC HEPATITIS B. ACCUMULATING EVIDENCE SUGGESTS THAT EPIGENETIC MODIFICATIONS REGULATE THE TRANSCRIPTIONAL ACTIVITY OF CCCDNA MINICHROMOSOMES. HOWEVER, IT REMAINS UNCLEAR HOW THE EPIGENETIC STATE OF CCCDNA AFFECTS ITS STABILITY. APPROACHES AND RESULTS: BY USING HBV INFECTION CELL MODELS AND IN VITRO AND IN VIVO RECOMBINANT CCCDNA (RCCCDNA) AND HBVCIRCLE MODELS, THE REDUCTION RATE OF HBV CCCDNA AND THE EFFICACY OF APOLIPOPROTEIN B MRNA EDITING ENZYME CATALYTIC SUBUNIT 3A (APOBEC3A)-MEDIATED AND CRISPR/CRISPR-ASSOCIATED 9 (CAS9)-MEDIATED CCCDNA TARGETING WERE COMPARED BETWEEN CCCDNAS WITH DISTINCT TRANSCRIPTIONAL ACTIVITIES. INTERFERON-ALPHA TREATMENT AND HEPATITIS B X PROTEIN (HBX) DELETION WERE APPLIED AS TWO STRATEGIES FOR CCCDNA REPRESSION. CHROMATIN IMMUNOPRECIPITATION AND MICROCOCCAL NUCLEASE ASSAYS WERE PERFORMED TO DETERMINE THE EPIGENETIC PATTERN OF CCCDNA. HBV CCCDNA LEVELS REMAINED STABLE IN NONDIVIDING HEPATOCYTES; HOWEVER, THEY WERE SIGNIFICANTLY REDUCED DURING CELL DIVISION, AND THE REDUCTION RATE WAS SIMILAR BETWEEN CCCDNAS IN TRANSCRIPTIONALLY ACTIVE AND TRANSCRIPTIONALLY REPRESSED STATES. STRIKINGLY, HBV RCCCDNA WITHOUT HBX EXPRESSION EXHIBITED A SIGNIFICANTLY LONGER PERSISTENCE IN MICE. THE CCCDNA WITH LOW TRANSCRIPTIONAL ACTIVITY EXHIBITED AN EPIGENETICALLY INACTIVE PATTERN AND WAS MORE DIFFICULT TO ACCESS BY APOBEC3A AND ENGINEERED CRISPR-CAS9. THE EPIGENETIC REGULATOR ACTIVATING CCCDNA INCREASED ITS VULNERABILITY TO APOBEC3A. CONCLUSIONS: HBV CCCDNA MINICHROMOSOMES IN DISTINCT EPIGENETIC TRANSCRIPTIONAL STATES SHOWED A SIMILAR REDUCTION RATE DURING CELL DIVISION BUT SIGNIFICANTLY DIFFERED IN THEIR ACCESSIBILITY AND VULNERABILITY TO TARGETED NUCLEASES AND ANTIVIRAL AGENTS. EPIGENETIC SENSITIZATION OF CCCDNA MAKES IT MORE SUSCEPTIBLE TO DAMAGE AND MAY POTENTIALLY CONTRIBUTE TO AN HBV CURE. 2022 5 5936 29 TARGETING HEPATITIS B VIRUS COVALENTLY CLOSED CIRCULAR DNA AND HEPATITIS B VIRUS X PROTEIN: RECENT ADVANCES AND NEW APPROACHES. CHRONIC HEPATITIS B VIRUS (HBV) INFECTION REMAINS A WORLDWIDE CONCERN AND PUBLIC HEALTH PROBLEM. TWO KEY ASPECTS OF THE HBV LIFE CYCLE ARE ESSENTIAL FOR VIRAL REPLICATION AND THUS THE DEVELOPMENT OF CHRONIC INFECTIONS: THE ESTABLISHMENT OF THE VIRAL MINICHROMOSOME, COVALENTLY CLOSED CIRCULAR (CCC) DNA, WITHIN THE NUCLEUS OF INFECTED HEPATOCYTES AND THE EXPRESSION OF THE REGULATORY HEPATITIS B VIRUS X PROTEIN (HBX). INTERESTINGLY, NUCLEAR HBX REDIRECTS HOST EPIGENETIC MACHINERY TO ACTIVATE CCCDNA TRANSCRIPTION. IN THIS PERSPECTIVE, WE PROVIDE AN OVERVIEW OF RECENT ADVANCES IN UNDERSTANDING THE REGULATION OF CCCDNA AND THE MECHANISTIC AND FUNCTIONAL ROLES OF HBX. WE ALSO DESCRIBE THE PROGRESS TOWARD TARGETING BOTH CCCDNA AND HBX FOR THERAPEUTIC PURPOSES. FINALLY, WE OUTLINE STANDING QUESTIONS IN THE FIELD AND PROPOSE COMPLEMENTARY CHEMICAL BIOLOGY APPROACHES TO ADDRESS THEM. 2019 6 5368 25 RECENT ADVANCES IN THE STUDY OF HEPATITIS B VIRUS COVALENTLY CLOSED CIRCULAR DNA. CHRONIC HEPATITIS B INFECTION IS CAUSED BY HEPATITIS B VIRUS (HBV) AND A TOTAL CURE IS YET TO BE ACHIEVED. THE VIRAL COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) IS THE KEY TO ESTABLISH A PERSISTENT INFECTION WITHIN HEPATOCYTES. CURRENT ANTIVIRAL STRATEGIES HAVE NO EFFECT ON THE PRE-EXISTING CCCDNA RESERVOIR. THEREFORE, THE STUDY OF THE MOLECULAR MECHANISM OF CCCDNA FORMATION IS BECOMING A MAJOR FOCUS OF HBV RESEARCH. THIS REVIEW SUMMARIZES THE CURRENT ADVANCES IN CCCDNA MOLECULAR BIOLOGY AND THE LATEST STUDIES ON THE ELIMINATION OR INACTIVATION OF CCCDNA, INCLUDING THREE MAJOR AREAS: (1) EPIGENETIC REGULATION OF CCCDNA BY HBV X PROTEIN, (2) IMMUNE-MEDIATED DEGRADATION, AND (3) GENOME-EDITING NUCLEASES. ALL THESE ASPECTS PROVIDE CLUES ON HOW TO FINALLY ATTAIN A CURE FOR CHRONIC HEPATITIS B INFECTION. 2017 7 3255 26 HEPATITIS B VIRUS X PROTEIN MEDIATED EPIGENETIC ALTERATIONS IN THE PATHOGENESIS OF HEPATOCELLULAR CARCINOMA. CHRONIC HEPATITIS B VIRUS (HBV) INFECTION IS A WORLDWIDE HEALTH PROBLEM. HEPATITIS B VIRUS X PROTEIN (HBX), A PLEIOTROPIC REGULATORY PROTEIN ENCODED BY HBV, IS NECESSARY FOR THE TRANSCRIPTION OF HBV COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) MINICHROMOSOMES, AND AFFECTS THE EPIGENETIC REGULATION OF HOST CELLS. THE EPIGENETIC REPROGRAMMING OF HBX ON HOST CELL GENOME IS STRONGLY INVOLVED IN HBV-RELATED HCC CARCINOGENESIS. HERE, WE REVIEW THE LATEST FINDINGS OF THE EPIGENETIC REGULATION INDUCED BY HBX PROTEIN IN HEPATOCELLULAR CARCINOMA (HCC), INCLUDING DNA METHYLATION, HISTONE MODIFICATION AND NON-CODING RNA EXPRESSION. THE INFLUENCE OF HBX ON THE EPIGENETIC REGULATION OF CCCDNA IS ALSO SUMMARIZED. IN ADDITION, PRELIMINARY STUDIES OF TARGETED DRUGS FOR EPIGENETIC CHANGES INDUCED BY HBX ARE ALSO DISCUSSED. THE EXPLORATION OF EPIGENETIC MARKERS AS POTENTIAL TARGETS WILL HELP TO DEVELOP NEW PREVENTION AND/OR TREATMENT METHODS FOR HBX-RELATED HCC. 2022 8 1178 29 CONTROL OF CCCDNA FUNCTION IN HEPATITIS B VIRUS INFECTION. THE TEMPLATE OF HEPATITIS B VIRUS (HBV) TRANSCRIPTION, THE COVALENTLY CLOSED CIRCULAR DNA (CCCDNA), PLAYS A KEY ROLE IN THE LIFE CYCLE OF THE VIRUS AND PERMITS THE PERSISTENCE OF INFECTION. NOVEL MOLECULAR TECHNIQUES HAVE OPENED NEW POSSIBILITIES TO INVESTIGATE THE ORGANIZATION AND THE ACTIVITY OF THE CCCDNA MINICHROMOSOME IN VIVO, AND RECENT ADVANCES HAVE STARTED TO SHED LIGHT ON THE COMPLEXITY OF THE MECHANISMS CONTROLLING CCCDNA FUNCTION. NUCLEAR CCCDNA ACCUMULATES IN HEPATOCYTE NUCLEI AS A STABLE MINICHROMOSOME ORGANIZED BY HISTONE AND NON-HISTONE VIRAL AND CELLULAR PROTEINS. IDENTIFICATION OF THE MOLECULAR MECHANISMS REGULATING CCCDNA STABILITY AND ITS TRANSCRIPTIONAL ACTIVITY AT THE RNA, DNA AND EPIGENETIC LEVELS IN THE COURSE OF CHRONIC HEPATITIS B (CH-B) INFECTION MAY REVEAL NEW POTENTIAL THERAPEUTIC TARGETS FOR ANTI-HBV DRUGS AND HENCE ASSIST IN THE DESIGN OF STRATEGIES AIMED AT SILENCING AND EVENTUALLY DEPLETING THE CCCDNA RESERVOIR. 2009 9 3794 37 INTERLEUKIN-33 MEDIATES BOTH IMMUNE-RELATED AND NON-IMMUNE-RELATED INHIBITORY EFFECTS AGAINST HEPATITIS B VIRUS. CHRONIC INFECTION BY HEPATITIS B VIRUS (HBV) IS ASSOCIATED WITH HIGH RISKS OF LIVER FIBROSIS, CIRRHOSIS AND HEPATOCELLULAR CARCINOMA. HBV COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) IN THE NUCLEUS OF INFECTED HEPATOCYTE SERVES AS TRANSCRIPTION TEMPLATE. NEITHER NATURAL RESOLUTION OF ACUTE INFECTION NOR CURRENT TREATMENT OPTIONS FOR CHRONIC INFECTION ARE BELIEVED TO CAUSE CCCDNA CLEARANCE. WE PREVIOUSLY SHOWED THAT INJECTION OF IL-33-EXPRESSING PLASMID FACILITATED CLEARANCE OF INTRAHEPATIC HBV DNA IN A MOUSE MODEL OF HBV PERSISTENCE. IN THIS WORK, HBV-TARGETING THERAPEUTIC EFFECTS OF IL-33 WERE FURTHER EXPLORED. MURINE IL-33 DELIVERED BY RECOMBINANT ADENO-ASSOCIATED VIRUS (AAV-MIL-33) INDUCED CLEARANCE OF BOTH SERUM HBV MARKERS AND INTRAHEPATIC HBV DNA IN TWO MOUSE MODELS OF HBV PERSISTENCE BASED ON REPLICON PLASMID AND RECOMBINANT CCCDNA (RCCCDNA) RESPECTIVELY. CLEARANCE WAS ASSOCIATED WITH SERUM ALT ELEVATIONS AND LIVER INFILTRATIONS BY CD4(+) AND CD8(+) T CELLS, INDICATING IL-33-INDUCED CELLULAR IMMUNE RESPONSES AGAINST HBV-HARBORING CELLS. ADOPTIVE TRANSFER OF SPLENOCYTES FROM AAV-MIL-33-CURED MICE WAS INDEED SUFFICIENT TO ENGENDER SIMILAR CLEARANCE IN RECIPIENT MICE. IN VITRO, INTRACELLULAR, INSTEAD OF EXTRACELLULAR, IL-33 WAS MAINLY RESPONSIBLE FOR REPRESSING VIRAL TRANSCRIPTION, PROTEIN PRODUCTION AND GENOME REPLICATION IN HUH7 CELLS TRANSFECTED WITH HBV REPLICON OR RCCCDNA. IL-33 WAS SHOWN TO BE RECRUITED ONTO RCCCDNA MINICHROMOSOME ACCOMPANIED BY LOSS OF TRANSCRIPTIONAL ACTIVATION EPIGENETIC MARKS. FINALLY, TRANSFECTION OF IL-33 INTO HBV-INFECTED HEPG2/NTCP CELLS RESULTED IN REDUCED TRANSCRIPTION, ANTIGEN EXPRESSION AND GENOME REPLICATION, SUGGESTING REPRESSION OF CANONICAL CCCDNA. THESE DATA DEMONSTRATED DIVERSE INHIBITORY EFFECTS ON HBV AND HBV-INFECTED CELLS MEDIATED BY IL-33, AND SUGGEST IL-33 AS AN INTERESTING THERAPEUTIC CANDIDATE. 2022 10 6115 31 THE EPIGENETIC CONTROL OF HEPATITIS B VIRUS MODULATES THE OUTCOME OF INFECTION. EPIGENETIC MODIFICATIONS ARE STABLE ALTERATIONS IN GENE EXPRESSION THAT DO NOT INVOLVE MUTATIONS OF THE GENETIC SEQUENCE ITSELF. IT HAS BECOME INCREASINGLY CLEAR THAT EPIGENETIC FACTORS CONTRIBUTE TO THE OUTCOME OF CHRONIC HEPATITIS B VIRUS (HBV) INFECTION BY AFFECTING CELLULAR AND VIRION GENE EXPRESSION, VIRAL REPLICATION AND THE DEVELOPMENT OF HEPATOCELLULAR CARCINOMA. HBV PERSISTS IN THE NUCLEUS OF INFECTED HEPATOCYTES AS A STABLE NON-INTEGRATED COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) WHICH FUNCTIONS AS A MINICHROMOSOME. THERE ARE TWO MAJOR FORMS OF HBV EPIGENETIC REGULATION: POSTTRANSLATIONAL MODIFICATION OF HISTONE PROTEINS ASSOCIATED WITH THE CCCDNA MINICHROMOSOME AND DNA METHYLATION OF VIRAL AND HOST GENOMES. THIS REVIEW EXPLORES HOW HBV CAN INTERPHASE WITH HOST EPIGENETIC REGULATION IN ORDER TO EVADE HOST DEFENCES AND TO PROMOTE ITS OWN SURVIVAL AND PERSISTENCE. WE FOCUS ON THE EFFECT OF CCCDNA BOUND-HISTONE MODIFICATIONS AND THE METHYLATION STATUS OF HBV DNA IN REGULATING VIRAL REPLICATION. INVESTIGATION OF HBV EPIGENETIC CONTROL HAS IMPORTANT CLINICAL CORRELATES WITH REGARDS TO THE DEVELOPMENT OF POTENTIAL THERAPEUTIC REGIMENS THAT WILL SUCCESSFULLY ERADICATE HBV INFECTION AND DEAL WITH HBV REACTIVATION IN THOSE UNDERGOING TREATMENT WITH DEMETHYLATING AGENTS. 2015 11 1052 30 CLINICAL IMPLICATIONS OF HEPATITIS B VIRUS RNA AND COVALENTLY CLOSED CIRCULAR DNA IN MONITORING PATIENTS WITH CHRONIC HEPATITIS B TODAY WITH A GAZE INTO THE FUTURE: THE FIELD IS UNPREPARED FOR A STERILIZING CURE. . CHRONIC HEPATITIS B VIRUS (HBV) INFECTION HAS LONG REMAINED A CRITICAL GLOBAL HEALTH ISSUE. COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) IS A PERSISTENT FORM OF THE HBV GENOME THAT MAINTAINS HBV CHRONICITY. DECADES OF EXTENSIVE RESEARCH RESULTED IN THE TWO THERAPEUTIC OPTIONS CURRENTLY AVAILABLE: NUCLEOT(S)IDE ANALOGS AND INTERFERON (IFN) THERAPY. A PLETHORA OF RELIABLE MARKERS TO MONITOR HBV PATIENTS HAS BEEN ESTABLISHED, INCLUDING THE RECENTLY DISCOVERED ENCAPSIDATED PREGENOMIC RNA IN SERUM, WHICH CAN BE USED TO DETERMINE TREATMENT END-POINTS AND TO PREDICT THE SUSCEPTIBILITY OF PATIENTS TO IFN. ADDITIONALLY, HBV RNA SPLICE VARIANTS AND CCCDNA AND ITS EPIGENETIC MODIFICATIONS ARE ASSOCIATED WITH THE CLINICAL COURSE AND RISKS OF HEPATOCELLULAR CARCINOMA (HCC) AND LIVER FIBROSIS. HOWEVER, NEW ANTIVIRALS, INCLUDING CRISPR/CAS9, APOBEC-MEDIATED DEGRADATION OF CCCDNA, AND T-CELL THERAPIES AIM AT COMPLETELY ELIMINATING HBV, AND IT IS CLEAR THAT THE DIAGNOSTIC ARSENAL FOR DEFINING THE LONG-AWAITED STERILIZING CURE IS MISSING. IN THIS REVIEW, WE DISCUSS THE CURRENTLY AVAILABLE TOOLS FOR DETECTING AND MEASURING HBV RNAS AND CCCDNA, AS WELL AS THE STATE-OF-THE-ART IN CLINICAL IMPLICATIONS OF THESE MARKERS, AND DEBATE NEEDS AND GOALS WITHIN THE CONTEXT OF THE STERILIZING CURE THAT IS SOON TO COME. 2018 12 4239 31 METHYLATION PROFILE OF HEPATITIS B VIRUS IS NOT INFLUENCED BY INTERFERON ALPHA IN HUMAN LIVER CANCER CELLS. INTERFERON (IFN) ALPHA IS USED FOR THE TREATMENT OF CHRONIC HEPATITIS B VIRUS (HBV) INFECTION, BUT THE MOLECULAR MECHANISMS UNDERLYING ITS ANTIVIRAL EFFECT HAVE NOT BEEN FULLY ELUCIDATED. EPIGENETIC MODIFICATIONS REGULATE THE TRANSCRIPTIONAL ACTIVITY OF COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) IN CELLS WITH CHRONIC HBV INFECTION. IFN?ALPHA HAS BEEN SHOWN TO MODIFY CCCDNA?BOUND HISTONES, BUT IT IS NOT KNOWN WHETHER THE ANTI?HBV EFFECT OF IFN?ALPHA INVOLVES METHYLATION OF CCCDNA. THE PRESENT STUDY AIMED TO DETERMINE WHETHER IFN?ALPHA INDUCED METHYLATION OF HBV CCCDNA IN A CELL?BASED MODEL IN WHICH HEPG2 CELLS WERE DIRECTLY INFECTED WITH WILD?TYPE HBV VIRIONS. METHYLATION STATUS OF HBV CCCDNA WAS ASSESSED USING GLOBAL DNA METHYLATION ELISA ASSAY, METHYLATION?SPECIFIC PCR AND BISULFITE SEQUENCING. IFN?ALPHA SUPPRESSED HBV DNA AND RNA TRANSCRIPTS, BUT METHYLATION PROFILES WERE SIMILAR BETWEEN THE CONTROL AND IFN?ALPHA TREATED GROUPS. CHROMATIN IMMUNOPRECIPITATION RESULTS REVEALED BINDING OF DNA METHYLTRANSFERASES (DNMT) 3A AND DNMT3B TO HBV CCCDNA AND TREATMENT WITH IFN?ALPHA SUPPRESSED THE RECRUITMENT OF DNMT3B TO CCCDNA. TAKEN TOGETHER, THESE RESULTS SUGGEST THAT IFN?ALPHA DOES NOT INDUCE METHYLATION OF HBV CCCDNA. THEREFORE, IT WAS CONCLUDED THAT METHYLATION IS UNLIKELY TO CONTRIBUTE TO THE ANTI?HBV EFFECT OF IFN?ALPHA IN HEPG2 CELLS, AND THAT ALTERNATIVE MECHANISMS NEED TO BE SOUGHT TO ENHANCE CCCDNA METHYLATION AS A NOVEL THERAPY AGAINST HBV. 2021 13 3901 23 LEAD (PB) AND NEURODEVELOPMENT: A REVIEW ON EXPOSURE AND BIOMARKERS OF EFFECT (BDNF, HDL) AND SUSCEPTIBILITY. LEAD (PB) IS A UBIQUITOUS ENVIRONMENTAL POLLUTANT AND A POTENT TOXIC COMPOUND. HUMANS ARE EXPOSED TO PB THROUGH INHALATION, INGESTION, AND SKIN CONTACT VIA FOOD, WATER, TOBACCO SMOKE, AIR, DUST, AND SOIL. PB ACCUMULATES IN BONES, BRAIN, LIVER AND KIDNEY. FETAL EXPOSURE OCCURS VIA TRANSPLACENTAL TRANSMISSION. THE MOST CRITICAL HEALTH EFFECTS ARE DEVELOPMENTAL NEUROTOXICITY IN INFANTS AND CARDIOVASCULAR EFFECTS AND NEPHROTOXICITY IN ADULTS. PB EXPOSURE HAS BEEN STEADILY DECREASING OVER THE PAST DECADES, BUT THERE ARE FEW RECENT EXPOSURE DATA FROM THE GENERAL EUROPEAN POPULATION; MOREOVER, NO SAFE PB LIMIT HAS BEEN SET. SENSITIVE BIOMARKERS OF EXPOSURE, EFFECT AND SUSCEPTIBILITY, THAT RELIABLY AND TIMELY INDICATE PB-ASSOCIATED TOXICITY ARE REQUIRED TO ASSESS HUMAN EXPOSURE-HEALTH RELATIONSHIPS IN A SITUATION OF LOW TO MODERATE EXPOSURE. THEREFORE, A SYSTEMATIC LITERATURE REVIEW BASED ON PUBMED ENTRIES PUBLISHED BEFORE JULY 2019 THAT ADDRESSED PB EXPOSURE AND BIOMARKERS OF EFFECT AND SUSCEPTIBILITY, NEURODEVELOPMENTAL TOXICITY, EPIGENETIC MODIFICATIONS, AND TRANSCRIPTOMICS WAS CONDUCTED. FINALLY INCLUDED WERE 58 ORIGINAL PAPERS ON PB EXPOSURE AND 17 STUDIES ON BIOMARKERS. THE BIOMARKERS THAT ARE LINKED TO PB EXPOSURE AND NEURODEVELOPMENT WERE GROUPED INTO EFFECT BIOMARKERS (SERUM BRAIN-DERIVED NEUROTROPHIC FACTOR (BDNF) AND SERUM/SALIVA CORTISOL), SUSCEPTIBILITY MARKERS (EPIGENETIC MARKERS AND GENE SEQUENCE VARIANTS) AND OTHER BIOMARKERS (SERUM HIGH-DENSITY LIPOPROTEIN (HDL), MATERNAL IRON (FE) AND CALCIUM (CA) STATUS). SERUM BDNF AND PLASMA HDL ARE POTENTIAL CANDIDATES TO BE FURTHER VALIDATED AS EFFECT MARKERS FOR ROUTINE USE IN HBM STUDIES OF PB, COMPLEMENTED BY MARKERS OF FE AND CA STATUS TO ALSO ADDRESS NUTRITIONAL INTERACTIONS RELATED TO NEURODEVELOPMENTAL DISORDERS. FOR SEVERAL MARKERS, A CAUSAL RELATIONSHIP WITH PB-INDUCED NEURODEVELOPMENTAL TOXICITY IS LIKELY. RESULTS ON BDNF ARE DISCUSSED IN RELATION TO ADVERSE OUTCOME PATHWAY (AOP) 13 ("CHRONIC BINDING OF ANTAGONIST TO N-METHYL-D-ASPARTATE RECEPTORS (NMDARS) DURING BRAIN DEVELOPMENT INDUCES IMPAIRMENT OF LEARNING AND MEMORY ABILITIES") OF THE AOP-WIKI. FURTHER STUDIES ARE NEEDED TO VALIDATE SENSITIVE, RELIABLE, AND TIMELY EFFECT BIOMARKERS, ESPECIALLY FOR LOW TO MODERATE PB EXPOSURE SCENARIOS. 2021 14 5226 41 PRMT5 RESTRICTS HEPATITIS B VIRUS REPLICATION THROUGH EPIGENETIC REPRESSION OF COVALENTLY CLOSED CIRCULAR DNA TRANSCRIPTION AND INTERFERENCE WITH PREGENOMIC RNA ENCAPSIDATION. CHRONIC HEPATITIS B VIRUS (HBV) INFECTION REMAINS A MAJOR HEALTH PROBLEM WORLDWIDE. THE COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) MINICHROMOSOME, WHICH SERVES AS THE TEMPLATE FOR THE TRANSCRIPTION OF VIRAL RNAS, PLAYS A KEY ROLE IN VIRAL PERSISTENCE. WHILE ACCUMULATING EVIDENCE SUGGESTS THAT CCCDNA TRANSCRIPTION IS REGULATED BY EPIGENETIC MACHINERY, PARTICULARLY THE ACETYLATION OF CCCDNA-BOUND HISTONE 3 (H3) AND H4, THE POTENTIAL CONTRIBUTIONS OF HISTONE METHYLATION AND RELATED HOST FACTORS REMAIN OBSCURE. HERE, BY SCREENING A SERIES OF METHYLTRANSFERASES AND DEMETHYLASES, WE IDENTIFIED PROTEIN ARGININE METHYLTRANSFERASE 5 (PRMT5) AS AN EFFECTIVE RESTRICTOR OF HBV TRANSCRIPTION AND REPLICATION. IN CELL CULTURE-BASED MODELS FOR HBV INFECTION AND IN LIVER TISSUES OF PATIENTS WITH CHRONIC HBV INFECTION, WE FOUND THAT SYMMETRIC DIMETHYLATION OF ARGININE 3 ON H4 ON CCCDNA WAS A REPRESSIVE MARKER OF CCCDNA TRANSCRIPTION AND WAS REGULATED BY PRMT5 DEPENDING ON ITS METHYLTRANSFERASE DOMAIN. MOREOVER, PRMT5-TRIGGERED SYMMETRIC DIMETHYLATION OF ARGININE 3 ON H4 ON THE CCCDNA MINICHROMOSOME INVOLVED AN INTERACTION WITH THE HBV CORE PROTEIN AND THE BRG1-BASED HUMAN SWI/SNF CHROMATIN REMODELER, WHICH RESULTED IN DOWN-REGULATION OF THE BINDING OF RNA POLYMERASE II TO CCCDNA. IN ADDITION TO THE INHIBITORY EFFECT ON CCCDNA TRANSCRIPTION, PRMT5 INHIBITED HBV CORE PARTICLE DNA PRODUCTION INDEPENDENTLY OF ITS METHYLTRANSFERASE ACTIVITY. FURTHER STUDY REVEALED THAT PRMT5 INTERFERED WITH PREGENOMIC RNA ENCAPSIDATION BY PREVENTING ITS INTERACTION WITH VIRAL POLYMERASE PROTEIN THROUGH BINDING TO THE REVERSE TRANSCRIPTASE-RIBONUCLEASE H REGION OF POLYMERASE, WHICH IS CRUCIAL FOR THE POLYMERASE-PREGENOMIC RNA INTERACTION. CONCLUSION: PRMT5 RESTRICTS HBV REPLICATION THROUGH A TWO-PART MECHANISM INCLUDING EPIGENETIC SUPPRESSION OF CCCDNA TRANSCRIPTION AND INTERFERENCE WITH PREGENOMIC RNA ENCAPSIDATION; THESE FINDINGS IMPROVE THE UNDERSTANDING OF EPIGENETIC REGULATION OF HBV TRANSCRIPTION AND HOST-HBV INTERACTION, THUS PROVIDING NEW INSIGHTS INTO TARGETED THERAPEUTIC INTERVENTION. (HEPATOLOGY 2017;66:398-415). 2017 15 4055 33 MAPPING OF HISTONE MODIFICATIONS IN EPISOMAL HBV CCCDNA UNCOVERS AN UNUSUAL CHROMATIN ORGANIZATION AMENABLE TO EPIGENETIC MANIPULATION. CHRONIC HEPATITIS B VIRUS (HBV) INFECTION AFFECTS 240 MILLION PEOPLE WORLDWIDE AND IS A MAJOR RISK FACTOR FOR LIVER FAILURE AND HEPATOCELLULAR CARCINOMA. CURRENT ANTIVIRAL THERAPY INHIBITS CYTOPLASMIC HBV GENOMIC REPLICATION, BUT IS NOT CURATIVE BECAUSE IT DOES NOT DIRECTLY AFFECT NUCLEAR HBV CLOSED CIRCULAR DNA (CCCDNA), THE GENOMIC FORM THAT TEMPLATES VIRAL TRANSCRIPTION AND SUSTAINS VIRAL PERSISTENCE. NOVEL APPROACHES THAT DIRECTLY TARGET CCCDNA REGULATION WOULD THEREFORE BE HIGHLY DESIRABLE. CCCDNA IS ASSEMBLED WITH CELLULAR HISTONE PROTEINS INTO CHROMATIN, BUT LITTLE IS KNOWN ABOUT THE REGULATION OF HBV CHROMATIN BY HISTONE POSTTRANSLATIONAL MODIFICATIONS (PTMS). HERE, USING A NEW CCCDNA CHIP-SEQ APPROACH, WE REPORT, TO OUR KNOWLEDGE, THE FIRST GENOME-WIDE MAPS OF PTMS IN CCCDNA-CONTAINING CHROMATIN FROM DE NOVO INFECTED HEPG2 CELLS, PRIMARY HUMAN HEPATOCYTES, AND FROM HBV-INFECTED LIVER TISSUE. WE FIND HIGH LEVELS OF PTMS ASSOCIATED WITH ACTIVE TRANSCRIPTION ENRICHED AT SPECIFIC SITES WITHIN THE HBV GENOME AND, SURPRISINGLY, VERY LOW LEVELS OF PTMS LINKED TO TRANSCRIPTIONAL REPRESSION EVEN AT SILENT HBV PROMOTERS. WE SHOW THAT TRANSCRIPTION AND ACTIVE PTMS IN HBV CHROMATIN ARE REDUCED BY THE ACTIVATION OF AN INNATE IMMUNITY PATHWAY, AND THAT THIS EFFECT CAN BE RECAPITULATED WITH A SMALL MOLECULE EPIGENETIC MODIFYING AGENT, OPENING THE POSSIBILITY THAT CHROMATIN-BASED REGULATION OF CCCDNA TRANSCRIPTION COULD BE A NEW THERAPEUTIC APPROACH TO CHRONIC HBV INFECTION. 2015 16 3189 36 HBX RELIEVES CHROMATIN-MEDIATED TRANSCRIPTIONAL REPRESSION OF HEPATITIS B VIRAL CCCDNA INVOLVING SETDB1 HISTONE METHYLTRANSFERASE. BACKGROUND & AIMS: MAINTENANCE OF THE COVALENTLY CLOSED CIRCULAR HBV DNA (CCCDNA) THAT SERVES AS A TEMPLATE FOR HBV TRANSCRIPTION IS RESPONSIBLE FOR THE FAILURE OF ANTIVIRAL THERAPIES. WHILE STUDIES IN CHRONIC HEPATITIS PATIENTS HAVE SHOWN THAT HIGH VIREMIA CORRELATES WITH HYPERACETYLATION OF CCCDNA-ASSOCIATED HISTONES, THE MOLECULAR MECHANISMS CONTROLLING CCCDNA STABILITY AND TRANSCRIPTIONAL REGULATION ARE STILL POORLY UNDERSTOOD. THIS STUDY AIMED TO DECIPHER THE ROLE OF CHROMATIN AND CHROMATIN MODIFIER PROTEINS ON HBV TRANSCRIPTION. METHODS: WE ANALYZED THE CHROMATIN STRUCTURE OF ACTIVELY TRANSCRIBED OR SILENCED CCCDNA BY INFECTING PRIMARY HUMAN HEPATOCYTES AND DIFFERENTIATED HEPARG CELLS WITH WILD-TYPE VIRUS OR VIRUS DEFICIENT (HBVX-) FOR THE EXPRESSION OF HEPATITIS B VIRUS X PROTEIN (HBX), THAT IS REQUIRED FOR HBV EXPRESSION. RESULTS: IN THE ABSENCE OF HBX, HBV CCCDNA WAS TRANSCRIPTIONALLY SILENCED WITH THE CONCOMITANT DECREASE OF HISTONE 3 (H3) ACETYLATION AND H3K4ME3, INCREASE OF H3 DI- AND TRI-METHYLATION (H3K9ME) AND THE RECRUITMENT OF HETEROCHROMATIN PROTEIN 1 FACTORS (HP1) THAT CORRELATE WITH CONDENSED CHROMATIN. SETDB1 WAS FOUND TO BE THE MAIN HISTONE METHYLTRANSFERASE RESPONSIBLE FOR THE DEPOSITION OF H3K9ME3 AND HBV REPRESSION. FINALLY, FULL TRANSCRIPTIONAL REACTIVATION OF HBVX- UPON HBX RE-EXPRESSION CORRELATED WITH AN INCREASE OF HISTONE ACETYLATION AND H3K4ME3, AND A CONCOMITANT DECREASE OF HP1 BINDING AND OF H3K9ME3 ON THE CCCDNA. CONCLUSION: UPON HBV INFECTION, CELLULAR MECHANISMS INVOLVING SETDB1-MEDIATED H3K9ME3 AND HP1 INDUCE SILENCING OF HBV CCCDNA TRANSCRIPTION THROUGH MODULATION OF CHROMATIN STRUCTURE. HBX IS ABLE TO RELIEVE THIS REPRESSION AND ALLOW THE ESTABLISHMENT OF ACTIVE CHROMATIN. 2015 17 442 23 ANTIVIRAL THERAPIES FOR HEPATITIS B VIRUS-RELATED HEPATOCELLULAR CARCINOMA. CHRONIC HEPATITIS B VIRUS (HBV) INFECTION IS A CRITICAL RISK FACTOR FOR THE CARCINOGENESIS AND PROGRESSION OF HEPATOCELLULAR CARCINOMA (HCC). IT PROMOTES HCC DEVELOPMENT BY INDUCING LIVER FIBROGENESIS, GENETIC AND EPIGENETIC ALTERATIONS, AND THE EXPRESSION OF ACTIVE VIRAL-CODED PROTEINS. EFFECTIVE ANTIVIRAL TREATMENTS INHIBIT THE REPLICATION OF HBV, REDUCE SERUM VIRAL LOAD AND ACCELERATE HEPATITIS B E ANTIGEN SERUM CONVERSION. TIMELY INITIATION OF ANTIVIRAL TREATMENT IS NOT ONLY ESSENTIAL FOR PREVENTING THE INCIDENCE OF HCC IN CHRONIC HEPATITIS B PATIENTS, BUT ALSO IMPORTANT FOR REDUCING HBV REACTIVATION, IMPROVING LIVER FUNCTION, REDUCING OR DELAYING HCC RECURRENCE, AND PROLONGING OVERALL SURVIVAL OF HBV-RELATED HCC PATIENTS AFTER CURATIVE AND PALLIATIVE THERAPIES. THE SELECTION OF ANTIVIRAL DRUGS, MONITORING OF INDICATORS SUCH AS HBV DNA AND HEPATITIS B SURFACE ANTIGEN, AND TIMELY RESCUE TREATMENT WHEN NECESSARY, ARE ESSENTIAL IN ANTIVIRAL THERAPIES FOR HBV-RELATED HCC. 2015 18 5715 33 SIRT3 RESTRICTS HEPATITIS B VIRUS TRANSCRIPTION AND REPLICATION THROUGH EPIGENETIC REGULATION OF COVALENTLY CLOSED CIRCULAR DNA INVOLVING SUPPRESSOR OF VARIEGATION 3-9 HOMOLOG 1 AND SET DOMAIN CONTAINING 1A HISTONE METHYLTRANSFERASES. HEPATITIS B VIRUS (HBV) INFECTION REMAINS A MAJOR HEALTH PROBLEM WORLDWIDE. MAINTENANCE OF THE COVALENTLY CLOSED CIRCULAR DNA (CCCDNA), WHICH SERVES AS A TEMPLATE FOR HBV RNA TRANSCRIPTION, IS RESPONSIBLE FOR THE FAILURE OF ERADICATING CHRONIC HBV DURING CURRENT ANTIVIRAL THERAPY. CCCDNA IS ASSEMBLED WITH CELLULAR HISTONE PROTEINS INTO CHROMATIN, BUT LITTLE IS KNOWN ABOUT THE REGULATION OF HBV CHROMATIN BY HISTONE POSTTRANSLATIONAL MODIFICATIONS. IN THIS STUDY, WE IDENTIFIED SILENT MATING TYPE INFORMATION REGULATION 2 HOMOLOG 3 (SIRT3) AS A HOST FACTOR RESTRICTING HBV TRANSCRIPTION AND REPLICATION BY SCREENING SEVEN MEMBERS OF THE SIRTUIN FAMILY, WHICH IS THE CLASS III HISTONE DEACETYLASE. ECTOPIC SIRT3 EXPRESSION SIGNIFICANTLY REDUCED TOTAL HBV RNAS, 3.5-KB RNA, AS WELL AS REPLICATIVE INTERMEDIATE DNA IN HBV-INFECTED HEPG2-NA(+) /TAUROCHOLATE COTRANSPORTING POLYPEPTIDE CELLS AND PRIMARY HUMAN HEPATOCYTES. IN CONTRAST, GENE SILENCING OF SIRT3 PROMOTED HBV TRANSCRIPTION AND REPLICATION. A MECHANISTIC STUDY FOUND THAT NUCLEAR SIRT3 WAS RECRUITED TO THE HBV CCCDNA, WHERE IT DEACETYLATED HISTONE 3 LYSINE 9. IMPORTANTLY, OCCUPANCY OF SIRT3 ON CCCDNA COULD INCREASE THE RECRUITMENT OF HISTONE METHYLTRANSFERASE SUPPRESSOR OF VARIEGATION 3-9 HOMOLOG 1 TO CCCDNA AND DECREASE RECRUITMENT OF SET DOMAIN CONTAINING 1A, LEADING TO A MARKED INCREASE OF TRIMETHYL-HISTONE H3 (LYS9) AND A DECREASE OF TRIMETHYL-HISTONE H3 (LYS4) ON CCCDNA. MOREOVER, SIRT3-MEDIATED HBV CCCDNA TRANSCRIPTIONAL REPRESSION INVOLVED DECREASED BINDING OF HOST RNA POLYMERASE II AND TRANSCRIPTION FACTOR YIN YANG 1 TO CCCDNA. FINALLY, HEPATITIS B VIRAL X PROTEIN COULD RELIEVE SIRT3-MEDIATED CCCDNA TRANSCRIPTIONAL REPRESSION BY INHIBITING BOTH SIRT3 EXPRESSION AND ITS RECRUITMENT TO CCCDNA. CONCLUSION: SIRT3 IS A HOST FACTOR EPIGENETICALLY RESTRICTING HBV CCCDNA TRANSCRIPTION BY ACTING COOPERATIVELY WITH HISTONE METHYLTRANSFERASE; THESE DATA PROVIDE A RATIONALE FOR THE USE OF SIRT3 ACTIVATORS IN THE PREVENTION OR TREATMENT OF HBV INFECTION. (HEPATOLOGY 2018). 2018 19 2240 33 EPIGENETIC MODULATION IN CHRONIC HEPATITIS B VIRUS INFECTION. THE HUMAN HEPATITIS B VIRUS (HBV) IS A SMALL-ENVELOPED DNA VIRUS CAUSING ACUTE AND CHRONIC HEPATITIS. DESPITE THE EXISTENCE OF AN EFFECTIVE PROPHYLACTIC VACCINE AND THE STRONG CAPACITY OF APPROVED ANTIVIRAL DRUGS TO SUPPRESS VIRAL REPLICATION, CHRONIC HBV INFECTION (CHB) CONTINUES TO BE A MAJOR HEALTH BURDEN WORLDWIDE. BOTH THE INABILITY OF THE IMMUNE SYSTEM TO RESOLVE CHB AND THE UNIQUE REPLICATION STRATEGY EMPLOYED BY HBV, WHICH FORMS A STABLE VIRAL COVALENTLY CLOSED CIRCULAR DNA (CCCDNA) MINICHROMOSOME IN THE HEPATOCYTE NUCLEUS, ENABLE INFECTION PERSISTENCE. KNOWLEDGE OF THE COMPLEX NETWORK OF INTERACTIONS THAT HBV ENGAGES WITH ITS HOST IS STILL LIMITED BUT ACCUMULATING EVIDENCE INDICATES THAT EPIGENETIC MODIFICATIONS OCCURRING BOTH ON THE CCCDNA AND ON THE HOST GENOME IN THE COURSE OF INFECTION ARE ESSENTIAL TO MODULATE VIRAL ACTIVITY AND LIKELY CONTRIBUTE TO PATHOGENESIS AND CANCER DEVELOPMENT. THUS, A DEEPER UNDERSTANDING OF EPIGENETIC REGULATORY PROCESSES MAY OPEN NEW VENUES TO CONTROL AND EVENTUALLY CURE CHB. THIS REVIEW SUMMARIZES MAJOR FINDINGS IN HBV EPIGENETIC RESEARCH, FOCUSING ON THE EPIGENETIC MECHANISMS REGULATING CCCDNA ACTIVITY AND THE MODIFICATIONS DETERMINED IN INFECTED HOST CELLS AND TUMOR LIVER TISSUES. 2020 20 6868 20 [PATHOGENESIS OF HEPATITIS B VIRUS-RELATED HEPATOCELLULAR CARCINOMA]. HEPATOCELLULAR CARCINOMA (HCC) IS ONE OF THE MOST COMMON CANCER WORLDWIDE. MOST OF THE HCC OCCUR IN DEVELOPING COUNTRIES. CHRONIC HEPATITIS B VIRUS (HBV) INFECTION IS AN IMPORTANT RISK FACTOR FOR HCC DEVELOPMENT. HBV INDUCES IMMUNE-MEDIATED CHRONIC HEPATITIS, LIVER INJURY, REGENERATION AND SCAR FORMING RESPONSES, LEADING TO AN INFLAMMATORY, FIBROTIC AND IMMUNE DEFICIENT MICROENVIRONMENT. HBV MAY INTEGRATE INTO HOST GENOME, INDUCING GENETIC ABNORMALITY AND ALTERING THE EXPRESSION OF HCC-RELATED GENES. HBV ALSO EXPRESSES ACTIVE PROTEINS SUCH AS X (HBX) AND S PROTEINS, WHICH MAY TRANS-ACTIVATE HCC-RELATED PROTEINS EXPRESSION, INTERACT WITH INTRACELLULAR SPECIFIC PROTEINS, ACTIVATE A VARIETY OF SIGNALING PATHWAYS, AND INDUCE ABERRANT EPIGENETIC MODIFICATIONS. HBV MUTATION ALSO HAS IMPACT ON HBV RELATED HCC DEVELOPMENT. 2016