title: The hepatitis B virus-encoded transcriptional trans-activator hbx appears to be a novel protein serine/threonine kinase.
abstract: To study the functional mechanism of the hepatitis B virus (HBV) X (hbx) gene product, we have expressed the hbx protein in E. coli and purified it by HPLC. The purified hbx protein was shown to be active in transactivating transcription directed by the LTR sequence of HIV-1. The hbx protein was found to have an intrinsic serine/threonine protein kinase activity. The hbx protein was detected in hepatitis B virions, and tryptic phosphopeptide maps of the hbx protein phosphorylated in the virion and of the in vitro phosphorylated bacterially expressed hbx protein were similar. Inactivation of the hbx protein by heat, protein-denaturing agents, or an ATP affinity analog, p-fluorosulfonylbenzoyl 5'-adenosine, resulted in loss of both protein kinase activity and trans-activation activity. These results suggest that the HBV-encoded trans-activator hbx is a novel protein kinase.
authors.affiliation: Department of Medicine, Stanford University School of Medicine, California 94305.
authors.forename: J Y
authors.initials: JY
authors.lastname: Wu
authors.forename: Z Y
authors.initials: ZY
authors.lastname: Zhou
authors.forename: A
authors.initials: A
authors.lastname: Judd
authors.forename: C A
authors.initials: CA
authors.lastname: Cartwright
authors.forename: W S
authors.initials: WS
authors.lastname: Robinson
mesh_terms: D001483:Base Sequence; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D015870:Gene Expression; D006515:Hepatitis B virus / Q000201:enzymology / Q000235:genetics* / Q000302:isolation & purification; D006801:Humans; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes; D010449:Peptide Mapping; D010957:Plasmids; D014176:Protein Biosynthesis; D015183:Restriction Mapping; D015534:Trans-Activators / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D054334:Viral Regulatory and Accessory Proteins; D014771:Virion / Q000201:enzymology / Q000235:genetics / Q000302:isolation & purification
chemical_list: D015345:Oligonucleotide Probes; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein