INTERACTION OF THE UV-DAMAGED DNA-BINDING PROTEIN WITH HEPATITIS-B VIRUS X-PROTEIN IS CONSERVED AMONG MAMMALIAN HEPADNAVIRUSES AND RESTRICTED TO TRANSACTIVATION-PROFICIENT X-INSERTION MUTANTS

We carried out a comparative analysis of several proposed host protein partners of the human hepatitis B virus X protein (HBx) using both th e GAL-4- and the LexA-based yeast two-hybrid system. We showed that th e interaction of HBx with the UV-damaged DNA-binding protein (UVDDB) i s positive in both yeast systems, detectable in cotransfected human ce lls, conserved by rodent hepadnavirus X proteins (known to transactiva te in human cells), and tightly correlated with the transactivation pr oficiency of X-insertion mutants. Taken together, our results strongly suggest that UVDDB is involved in X-mediated transactivation.