Chronic Hepatitis B Virus (HBV) infection is a major risk factor in development of hepatocellular carcinoma (HCC). Despite the HBV vaccine, the World Health Organization (WHO) reports 250 million people are chronically infected with HBV. Current therapies for HBV infection or treatment of liver cancer are ineffective. To reduce the risk for liver cancer, new and effective therapies are needed, targeting essential mechanisms of viral replication and liver cancer pathogenesis. In this proposal we are investigating a novel epigenetic mechanism that contributes both to HBV biosynthesis and HBV-associated liver cancer. This mechanism involves the chromatin modifying Polycomb Repressive Complex 2 (PRC2) that silences genes by H3K27 trimethylation, the DEAD box helicase DDX5 that remodels RNA protein (RNP) complexes, and the long noncoding RNA (lncRNA) HOTAIR. PRC2 silences transcription of >1000 genes and binds >9,000 lncRNAs, including HOTAIR. However, how PRC2 targets repression of specific genes is not yet understood. Our studies have identified the RNA helicase DDX5 as a regulator of PRC2-mediated gene repression, acting by stabilizing the essential PRC2 subunit SUZ12, via regulation of RNP complexes formed with HOTAIR. Significantly, knockdown of either DDX5 and/or HOTAIR enabled re-expression of specific PRC2-repressed genes, namely, EpCAM and pluripotency genes (NANOG, OCT4, and SOX2.) Concerning the role of this epigenetic mechanism in HBV infection and HCC pathogenesis, we have shown the HBV encoded X protein, a cofactor in hepatocarcinogenesis, signals the proteasomal degradation of SUZ12 protein. The downregulation of SUZ12 results in loss of PRC2 function and re-expression of EpCAM and pluripotency genes during HBV replication and in HBV-associated liver tumors. In addition to SUZ12, we have also found that DDX5 is downregulated during HBV replication and in poor prognosis HBV-induced HCCs by an unknown mechanism. Importantly, downregulation of SUZ12 and DDX5 is advantageous to virus biosynthesis. In this competitive renewal application, our working hypothesis is that DDX5 functions to stabilize SUZ12 and the PRC2/HOTAIR complex, thus promoting PRC2-mediated transcriptional repression of both cellular and viral genes. How viral infection deregulates this mechanism is not understood. Accordingly we will investigate:
in Aim1, the role of DDX5 in SUZ12/PRC2 function, and how HBV infection deregulates this complex;
in Aim2 the role of DDX5 in HBV replication, and in Aim3 the mechanism of DDX5 down-regulation during HBV infection, and its role in HBV-mediated tumorigenesis. Impact: The proposed studies will elucidate a novel epigenetic mechanism that regulates both HBV biosynthesis and HBV-mediated oncogenic transformation. Our studies have the potential to identify novel therapy targets for HBV infection and liver cancer, e.g., the RNA helicase DDX5 and molecules that regulate DDX5.

Public Health Relevance

Public Statement. Liver cancer has the fastest growing death rate in the US, relative to other cancers; chronic Hepatitis B Virus infection is a major factor for liver cancer development. New and effective therapies and biomarkers are needed. Our studies aim to identify new therapies and biomarkers for HBV-mediated liver cancer.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Cancer Etiology Study Section (CE)
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Sherker, Averell H
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Purdue University
Other Basic Sciences
Schools of Veterinary Medicine
West Lafayette
United States
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Mani, Saravana Kumar Kailasam; Andrisani, Ourania (2018) Interferon signaling during Hepatitis B Virus (HBV) infection and HBV-associated hepatocellular carcinoma. Cytokine :
Zhang, Hao; Zhang, Yanqiu; Zhu, Xiaoyun et al. (2018) DEAD Box Protein 5 Inhibits Liver Tumorigenesis by Stimulating Autophagy via Interaction with p62/SQSTM1. Hepatology :
Diab, Ahmed; Foca, Adrien; Zoulim, Fabien et al. (2018) The diverse functions of the hepatitis B core/capsid protein (HBc) in the viral life cycle: Implications for the development of HBc-targeting antivirals. Antiviral Res 149:211-220
Mani, Saravana Kumar Kailasam; Andrisani, Ourania (2018) Hepatitis B Virus-Associated Hepatocellular Carcinoma and Hepatic Cancer Stem Cells. Genes (Basel) 9:
Diab, Ahmed; Foca, Adrien; Fusil, Floriane et al. (2017) Polo-like-kinase 1 is a proviral host factor for hepatitis B virus replication. Hepatology 66:1750-1765
Fan, H; Cui, Z; Zhang, H et al. (2017) DNA demethylation induces SALL4 gene re-expression in subgroups of hepatocellular carcinoma associated with Hepatitis B or C virus infection. Oncogene 36:2435-2445
Mani, Saravana Kumar Kailasam; Zhang, Hao; Diab, Ahmed et al. (2016) EpCAM-regulated intramembrane proteolysis induces a cancer stem cell-like gene signature in hepatitis B virus-infected hepatocytes. J Hepatol 65:888-898
Fan, H; Zhang, H; Pascuzzi, P E et al. (2016) Hepatitis B virus X protein induces EpCAM expression via active DNA demethylation directed by RelA in complex with EZH2 and TET2. Oncogene 35:715-26
Zhang, Hao; Xing, Zheng; Mani, Saravana Kumar Kailasam et al. (2016) RNA helicase DEAD box protein 5 regulates Polycomb repressive complex 2/Hox transcript antisense intergenic RNA function in hepatitis B virus infection and hepatocarcinogenesis. Hepatology 64:1033-48
Zhang, Hao; Diab, Ahmed; Fan, Huitao et al. (2015) PLK1 and HOTAIR Accelerate Proteasomal Degradation of SUZ12 and ZNF198 during Hepatitis B Virus-Induced Liver Carcinogenesis. Cancer Res 75:2363-74

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