title: The hepatitis B virus X-associated protein, XAP3, is a protein kinase C-binding protein.
abstract: The hepatitis B virus X protein induces transcriptional activation of a wide variety of viral and cellular genes. In addition to its ability to interact directly with many nuclear transcription factors, several reports indicate that the X protein stimulates different cytoplasmic kinase signal cascades. Using the yeast two-hybrid screen, we have isolated a clone designated X-associated protein 3 (XAP3) that encodes a human homolog of the rat protein kinase C-binding protein. One of the activation domains of X (amino acids 90-122) is required for binding to XAP3, while the NH2-terminal part of XAP3 is necessary for binding to X. Both X and XAP3 bound specifically to the eta PKC isoenzyme synthesized in rabbit reticulocyte lysates. Overexpression of XAP3 enhanced X transactivation activity. These results support earlier findings that one of the mechanisms of transactivation by X is through involvement with the cellular protein kinase C pathway.
authors.affiliation: Moffitt Cancer Center & Research Institute, Department of Medical Microbiology/Immunology, College of Medicine, University of South Florida, Tampa, Florida 33612, USA.
authors.forename: Y S
authors.initials: YS
authors.lastname: Cong
authors.forename: Y L
authors.initials: YL
authors.lastname: Yao
authors.forename: W M
authors.initials: WM
authors.lastname: Yang
authors.forename: N
authors.initials: N
authors.lastname: Kuzhandaivelu
authors.forename: E
authors.initials: E
authors.lastname: Seto
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000378:metabolism*; D018076:DNA, Complementary / Q000737:chemistry; D006801:Humans; D007527:Isoenzymes / Q000378:metabolism; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism*; D011817:Rabbits; D051381:Rats; D015534:Trans-Activators / Q000378:metabolism*; D015533:Transcriptional Activation; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D002352:Carrier Proteins; D018076:DNA, Complementary; D007527:Isoenzymes; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein; D011493:Protein Kinase C