title: Interaction of hepatitis B viral oncoprotein with cellular target HBXIP dysregulates centrosome dynamics and mitotic spindle formation.
abstract: Hepatitis B virus infection is associated with hepatocellular carcinoma, claiming 1 million lives annually worldwide. To understand the carcinogenic mechanism of hepatitis B virus-encoded oncoprotein HBx, we explored the function of HBx interaction with its cellular target HBXIP. Previously, we demonstrated that viral HBx and cellular HBXIP control mitotic spindle formation, regulating centrosome splitting. By using various fragments of HBx, we determined that residues (137)CRHK(140) within HBx are necessary for binding HBXIP. Mutation of the (137)CRHK(140) motif in HBx abolished its ability to bind HBXIP and to dysregulate centrosome dynamics in HeLa and immortal diploid RPE-1 cells. Unlike wild-type HBx, which targets to centrosomes as determined by subcellular fractionation and immunofluorescence microscopy, HBx mutants failed to localize to centrosomes. Overexpression of viral HBx wild-type protein and knockdown of endogenous HBXIP altered centrosome assembly and induced modifications of pericentrin and centrin-2, two essential proteins required for centrosome formation and function, whereas HBXIP nonbinding mutants of HBx did not. Overexpression of HBXIP or fragments of HBXIP that bind HBx neutralized the effects of viral HBx on centrosome dynamics and spindle formation. These results suggest that HBXIP is a critical target of viral HBx for promoting genetic instability through formation of defective spindles and subsequent aberrant chromosome segregation.
authors.affiliation: Program on Apoptosis and Cell Death Research, Burnham Institute for Medical Research, 10901 N. Torrey Pines Road, La Jolla, CA 92037, USA.
authors.forename: Yunfei
authors.initials: Y
authors.lastname: Wen
authors.forename: Vladislav S
authors.initials: VS
authors.lastname: Golubkov
authors.forename: Alex Y
authors.initials: AY
authors.lastname: Strongin
authors.forename: Wei
authors.initials: W
authors.lastname: Jiang
authors.forename: John C
authors.initials: JC
authors.lastname: Reed
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics / Q000502:physiology*; D001483:Base Sequence; D002460:Cell Line; D018385:Centrosome / Q000502:physiology; D017931:DNA Primers / Q000235:genetics; D042822:Genomic Instability; D006367:HeLa Cells; D006511:Hepatitis B Antigens / Q000235:genetics / Q000502:physiology*; D006515:Hepatitis B virus / Q000235:genetics / Q000472:pathogenicity / Q000502:physiology*; D006801:Humans; D008969:Molecular Sequence Data; D009154:Mutation; D009856:Oncogene Proteins, Viral / Q000235:genetics / Q000502:physiology*; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D008941:Spindle Apparatus / Q000235:genetics / Q000502:physiology; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D017931:DNA Primers; D006511:Hepatitis B Antigens; C110719:LAMTOR5 protein, human; D009856:Oncogene Proteins, Viral; D011994:Recombinant Proteins; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein