Genomes and Genes
Hepatitis B virus replication and DDB1
Principal Investigator: Betty L Slagle
Abstract: DESCRIPTION (provided by applicant): Chronic hepatitis B virus (HBV) infection affects approximately 350 million people worldwide and is a significant risk factor for severe liver disease, including hepatocellular carcinoma (HCC). The role of HBV in mediating carcinogenesis is complex and includes integration of viral DNA into host chromosomes, the host immune system, and expression of the viral regulatory HBx protein. Our laboratory studies HBx, a small protein required for virus replication in vivo that is also involved in carcinogenesis We and others have shown that the interaction of HBx with cellular damaged DNA binding protein (DDB1) is critical for HBV replication. However, the functional implications of this interaction to viral replication and pathogenesis remain elusive. DDB1 is an adaptor protein for the Cul4-DDB1 E3 ligase complex, and acts in part by recruiting cellular DDB1- Cullin Accessory Factors (DCAFs) that act as substrate receptors to recruit additional cellular targets for ubiquitination and proteasome degradation. In this manner, DDB1 regulates diverse cellular functions such as DNA replication, cell cycle, innate immunity, and damaged DNA repair. We hypothesize that HBx acts as a viral DCAF, and displaces one or more cellular DCAFs from the Cul4-DDB1 complex, thereby modifying the cellular environment to favor virus replication. Human liver chimeric mice, in which human hepatocytes are engrafted into immunodeficient mice, provide the best, most biologically relevant model system to investigate the impact of HBV replication on Cul4-DDB1-DCAF complexes. In Specific Aim 1, an immunoprecipitation/mass spectrometry (MS) approach will be used to identify the Cul4-DDB1-DCAF profile of uninfected human liver, providing new insights into DDB1 pathways important to normal liver physiology. This will be compared to the Cul4-DDB1-DCAF profile from HBV-infected hepatocytes originating from the same donor liver, using quantitative MS analyses to compare relative binding levels of DCAFs to DDB1. In Specific Aim 2, the importance of HBx-DDB1 binding to DDB1 pathways will be investigated. To determine whether HBV activates the DNA damage response (DDR) as part of its acute replication strategy, uninfected and HBV- infected human liver tissue from chimeric mice will be examined by western blot for evidence of the DDR marker, phosphorylated histone H2AX. To determine whether HBx-inactivation of interferon signaling occurs through HBx-DDB1 binding, the ability of HBx mutants that cannot bind DDB1 to inhibit interferon signaling will be evaluated in vitro. Additionally, MS data will be mined for evidence that HBV replication induces recruitment of immune regulatory proteins to the Cul4-DDB1 complex. In summary, viruses are adept at targeting cellular pathways that benefit viral replication. The proposed studies will elucidate the impact of HBV replication on the cellular ubiquitination and degradation machinery using the innovative human liver chimeric animal model. This important new knowledge will reveal virus-induced changes at the post-translational level, and is predicted to provide mechanistic insight into new strategies through which to treat chronic HBV infection and prevent liver disease.
Funding Period: 2013-07-01 - 2015-06-30
more information: NIH RePORT
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- University of Maryland Greenebaum Cancer Center Support GrantKevin J Cullen; Fiscal Year: 2013..Reflecting our remarkable and continued growth, UMGCC seeks to renew its CCSG to enhance and expand its efforts in high-quality and clinically relevant cancer research. ..
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- USC Research Center for Liver DiseaseNeil Kaplowitz; Fiscal Year: 2013....
- Middle Atlantic Regional Center for Excellence for Biodefense and Emerging InfectMYRON MAX LEVINE; Fiscal Year: 2013..abstract_text> ..
- Center for the Study of Innate Immunity to HCV InfectionMichael J Gale; Fiscal Year: 2013..Our studies are linked with the U19 Clinical Core, and Projects 2 and 3 to feature translational approaches aimed at defining the virus-host interface that controls hepatic innate immunity and HCV infection. ..
- Regulation of Nucleotide Excision Repair by ProteolysisPengbo Zhou; Fiscal Year: 2013..abstract_text> ..
- Characterization of novel regulators of amino acid-sensitive mTORC1 signalingLAWRENCE SCHWEITZER; Fiscal Year: 2013..3. Interrogate the role of the amino acid-sensitive mTORC1 pathway in Hepatitis B virus infection. ..
- Blocking toll-like receptor 4 signaling as therapy in hepatic fibrosisBERND G SCHNABL; Fiscal Year: 2013..During the time of the award I will continue basic research to study liver fibrosis with an emphasis on "translational medicine" - taking the latest research and translating it into clinical therapies. ..
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- Immune Control and Evasion during Acute HCV InfectionGEORG MICHAEL LAUER; Fiscal Year: 2013..abstract_text> ..
- Mechanism(s) of Hepatocyte Transformation by the Hepatitis B Virus X ProteinOurania M Andrisani; Fiscal Year: 2013..Plk1 inhibitors are in clinical trials for other types of cancer and could serve as therapy for HBV-HCC. Our studies hold promise to reveal novel therapy targets and biomarkers for HBV-HCC. ..
- The role of innate immune evasion in hepatitis C virus infectionYPE PETER DE JONG; Fiscal Year: 2013..Results obtained by these experiments can help prioritize which immunomodulatory therapies should best be pursued into clinical development. ..