title: HBxAPα/Rsf-1-mediated HBx-hBubR1 interactions regulate the mitotic spindle checkpoint and chromosome instability.
abstract: Hepatitis B virus (HBV) X protein (HBx), encoded by the HBV genome, is involved in the development of HBV-mediated liver cancer, whose frequency is highly correlated with chromosomal instability (CIN). We reported previously that HBx induces mitotic checkpoint dysfunction by targeting the human serine/threonine kinase BubR1 (hBubR1). However, the underlying mechanism remained unresolved. Here, we show that HBx protein-associated protein α (HBxAPα)/Rsf-1 associates with hBubR1 and HBx in the chromatin fraction during mitosis. Depletion of HBxAPα/Rsf-1 abolished the interaction between HBx and hBubR1, indicating that HBxAPα/Rsf-1 mediates these interactions. Knockdown of HBxAPα/Rsf-1 with small interfering RNA did not affect the recruitment of hBubR1 to kinetochores; however, it did significantly impair HBx targeting to kinetochores. A deletion mutant analysis revealed that two Kunitz domains of HBx, the Cdc20-binding domain of hBubR1 and full-length of HBxAPα/Rsf-1 were essential for these interactions. Thus, binding of HBx to hBubR1, stabilized by HBxAPα/Rsf-1, significantly attenuated hBubR1 binding to Cdc20 and consequently increased the rate of mitotic aberrations. Collectively, our data show that the HBx impairs hBubR1 function and induces CIN through HBxAPα/Rsf-1, providing a novel mechanism for induction of genomic instability by a viral pathogen in hepatocarcinogenesis.
authors.affiliation: Department of Biochemistry and Molecular Biology, Ajou University School of Medicine and the Graduate School of Molecular Science and Technology, Ajou University, Suwon, South Korea.
authors.forename: Sunyoung
authors.initials: S
authors.lastname: Chae
authors.forename: Jae-Hoon
authors.initials: JH
authors.lastname: Ji
authors.forename: Soon-Hwan
authors.initials: SH
authors.lastname: Kwon
authors.forename: Ho-Soo
authors.initials: HS
authors.lastname: Lee
authors.forename: Jung Mi
authors.initials: JM
authors.lastname: Lim
authors.forename: Dongmin
authors.initials: D
authors.lastname: Kang
authors.forename: Chang-Woo
authors.initials: CW
authors.lastname: Lee
authors.forename: Hyeseong
authors.initials: H
authors.lastname: Cho
mesh_terms: D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D043171:Chromosomal Instability; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D018386:Kinetochores / Q000378:metabolism; D008113:Liver Neoplasms / Q000378:metabolism / Q000473:pathology*; D059566:M Phase Cell Cycle Checkpoints; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D025941:Protein Interaction Mapping; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; D034741:RNA, Small Interfering; C452851:RSF1 protein, human; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein; C577488:CDC20 protein, human; C584277:BUB1 protein, human; C090464:Bub1 spindle checkpoint protein; D017346:Protein Serine-Threonine Kinases