HBV X protein targets HIV tat-binding protein 1

The HBV X protein (HBx) is implicated in infection and development of hepat ocellular carcinoma. HBx has a pleiotropic effect on cells, suggesting mult iple targets in the virus-host cell interaction. We employed the cytoplasmi c-based two-hybrid screen and identified the HIV Tat-binding protein 1 (Tbp 1) as a novel HBx interacting protein. Tbp1 interacts in vivo with HBx both in yeast and in animal cells. This interaction maps to the functionally im portant ATP-binding motif of Tbp1. Furthermore, HBx and Tbp1 interaction is functionally significant and regulates HBV transcription. Tbpl homologues, such as Sug1, are known members of the proteasome 19S regulatory cap parti cle and have also been implicated in transcription coactivation. Remarkably , Tbp1 and Sug1 interact with multiple viral effector proteins including HI V Tat, SV40 large T antigen, and adenovirus E1A, establishing these protein s as important targets of the viral oncogenes. (C) 2001 Academic Press.