title: Inhibition of hepatitis B virus replication by cIAP2 involves accelerating the ubiquitin-proteasome-mediated destruction of polymerase.
abstract: Cellular inhibitor of apoptosis protein 2 (cIAP2) is a potent suppressor of apoptotic cell death. We have shown previously that cIAP2 is involved in the tumor necrosis factor alpha (TNF-α)-induced anti-hepatitis B virus (HBV) response; however, the mechanism for this antiviral effect remains unclear. In the present study, we demonstrate that cIAP2 can significantly reduce the levels of HBV DNA replication intermediates but not the total viral RNA or core protein levels. Domain-mapping analysis revealed that the carboxy-terminal domains of cIAP2 were indispensable for this anti-HBV ability and that an E3 ligase-deficient mutant of cIAP2 (termed cIAP2*) completely lost its antiviral activity. We further identified HBV polymerase as the target of cIAP2. Overexpression of cIAP2 but not cIAP2* reduced polymerase protein levels, while cIAP2 knockdown increased polymerase expression. In addition, we observed that cIAP2 promoted the degradation of the viral polymerase through a proteasome-dependent pathway. Further experiments demonstrated that cIAP2 can bind to polymerase and promote its polyubiquitylation. Finally, we found that cIAP2 downregulated the encapsidation of HBV pregenomic RNA. Taken together, these data reveal a novel mechanism for the inhibition of HBV replication by cIAP2 via acceleration of the ubiquitin-proteasome-mediated decay of polymerase and reduction of the encapsidation of HBV pregenomic RNA, making this mechanism a novel strategy for HBV therapy.
authors.affiliation: Key Laboratory of Medical Molecular Virology, Shanghai Medical College, Fudan University, 138 Yixueyuan Road, Shanghai 200032, China.
authors.forename: Zekun
authors.initials: Z
authors.lastname: Wang
authors.forename: Jinjing
authors.initials: J
authors.lastname: Ni
authors.forename: Jianhua
authors.initials: J
authors.lastname: Li
authors.forename: Bisheng
authors.initials: B
authors.lastname: Shi
authors.forename: Yang
authors.initials: Y
authors.lastname: Xu
authors.forename: Zhenghong
authors.initials: Z
authors.lastname: Yuan
mesh_terms: D000075747:Baculoviral IAP Repeat-Containing 3 Protein; D002460:Cell Line; D004279:DNA, Viral / Q000378:metabolism; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism*; D015870:Gene Expression; D055785:Gene Knockdown Techniques; D006515:Hepatitis B virus / Q000276:immunology / Q000502:physiology*; D022781:Hepatocytes / Q000821:virology; D006801:Humans; D051034:Inhibitor of Apoptosis Proteins / Q000235:genetics / Q000378:metabolism*; D019384:Nucleic Acid Synthesis Inhibitors; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D025941:Protein Interaction Mapping; D012367:RNA, Viral / Q000378:metabolism; D025801:Ubiquitin / Q000378:metabolism*; D044767:Ubiquitin-Protein Ligases; D014764:Viral Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D019065:Virus Assembly; D014779:Virus Replication
chemical_list: D004279:DNA, Viral; D051034:Inhibitor of Apoptosis Proteins; D019384:Nucleic Acid Synthesis Inhibitors; D012367:RNA, Viral; D025801:Ubiquitin; D014764:Viral Proteins; C494832:BIRC3 protein, human; D000075747:Baculoviral IAP Repeat-Containing 3 Protein; D044767:Ubiquitin-Protein Ligases; D004259:DNA-Directed DNA Polymerase; D046988:Proteasome Endopeptidase Complex