title: XAP2, a novel hepatitis B virus X-associated protein that inhibits X transactivation.
abstract: The hepatitis B virus X protein is a promiscuous transcriptional transactivator. Transactivation by the X protein is most likely mediated through binding to different cellular factors. Using the yeast two-hybrid method, we have isolated a clone that encodes a novel X-associated cellular protein: XAP2. X and XAP2 interactions also occur in vitro. Antiserum raised against XAP2 recognizes a cytoplasmic protein with an apparent molecular mass of 36 kDa. The interaction between X and XAP2 requires a small region on X containing amino acids 13-26. From Northern blot analyses, XAP2 is ubiquitously expressed in both liver-derived and non-liver-derived cell lines as well as in normal non-liver tissues. In contrast, XAP2 is expressed in very low level in the normal human liver. In transfection assays, overexpression of XAP2 abolishes transactivation by the X protein. Based on these results, we suggest that XAP2 is an important cellular negative regulator of the X protein, and that X-XAP2 interaction may play a role in HBV pathology.
authors.affiliation: Moffitt Cancer Center and Research Institute, Department of Medical Microbiology and Immunology, University of South Florida, Tampa 33612, USA.
authors.forename: N
authors.initials: N
authors.lastname: Kuzhandaivelu
authors.forename: Y S
authors.initials: YS
authors.lastname: Cong
authors.forename: C
authors.initials: C
authors.lastname: Inouye
authors.forename: W M
authors.initials: WM
authors.lastname: Yang
authors.forename: E
authors.initials: E
authors.lastname: Seto
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D015152:Blotting, Northern; D002467:Cell Nucleus / Q000737:chemistry; D003001:Cloning, Molecular; D003593:Cytoplasm / Q000737:chemistry; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D004926:Escherichia coli / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008113:Liver Neoplasms / Q000737:chemistry; D008969:Molecular Sequence Data; D011506:Proteins / Q000737:chemistry / Q000235:genetics / Q000494:pharmacology*; D012333:RNA, Messenger; D012441:Saccharomyces cerevisiae / Q000235:genetics; D014018:Tissue Distribution; D015534:Trans-Activators / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000235:genetics; D015533:Transcriptional Activation / Q000187:drug effects*; D014407:Tumor Cells, Cultured; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D018076:DNA, Complementary; D047908:Intracellular Signaling Peptides and Proteins; D011506:Proteins; D012333:RNA, Messenger; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C103265:aryl hydrocarbon receptor-interacting protein; C057628:hepatitis B virus X protein