The Effect Of High Mobility Group Protein B1on Virus Lifecycle

Hepatitis C virus (HCV) is a single positive-strand RNA virus, which has infectedapproximately170million people worldwide, and causes serious liver diseases suchas chronic hepatitis, cirrhosis, and hepatocellular carcinoma. PEG-interferoncombined with ribavirin is the classical therapy, but at least50%of patients infectedby genotype1do not response to this treatment. Therefore, new therapies for HCVinfection are badly demanded, and the elucidation of HCV lifecycle will provide newtherapeutic targets for antiviral research. High mobility group protein B1(HMGB1) isa non-histone protein mainly located in the nuclear, where it modulates the structureand function of chromatin. As to the role in virus infection, HMGB1is able to inhibitthe replication of dengue virus and vesicular stomatitis virus in host cells, as well asenhancing the replication of influenza virus. The main purpose of our project is tostudy the role of HMGB1in HCV infection.To study the function of HMGB1, we blocked its functional mRNA inhepatocellular carcinoma cell line Huh7, Huh7.5, and HLCZ01by RNAi, includingsiRNA and shRNA. Then we infected Huh7.5and HLCZ01with HCV, and Huh7withNDV. HMGB1RNAi decreases the virus replication in these cells. HMGB1over-expression increases HCV level in HLCZ01, and the IFNβ mRNA levelpositively correlates to the virus levels. These results indicate that HMGB1enhancesvirus replication by some ways other than interfering host cell innate immuneresponse. Immuno-fluorescence localization revealed HMGB1translocation fromnuclear to cytoplasm after HCV infection. Co-immunoprecipitation and RNA bindingprotein co-immunoprecipitation showed that HMGB1bound to HCV negative-strandRNA, not certain viral proteins like core/NS2/NS5A. These data suggests thathepatocellular HMGB1translocates from nuclear to cytoplasm, then binds to HCVnegative-strand RNA to enhance HCV replication. Our study will shed new light onthe function of HMGB1during virus infection and the lifecycle of HCV, as well asproviding a new therapeutic target and research system for antiviral investigation.