Human hepatitis B virus polymerase interacts with the molecular chaperoninHsp60

Previous studies showed that hepatitis B virus polymerase (HBV Pol) interac ts with host factors such as the Hsp90 complex, which is a critical step in viral genome replication. In this report, we propose that another chaperon e, Hsp60, interacts with human HBV Pol and that this is a very important st ep for maturation of human HBV Pol into the active state. In the immunoprec ipitation of recombinant human HBV Pol expressed in insect cells with the r ecombinant baculovirus expression system, the 60-kDa protein was coimmunopr ecipitated with Pol and the protein was identified as Hsp60 through peptide sequencing and immunogenic analysis with an anti-Hsp60 antibody. In vitro experiments showed that Hsp60 strongly affected human HBV Pol activity in t hat (i) blocking of Hsp60 by the protein-specific antibody reduced human HB V Pol activity, (ii) the activity was increased by addition of Hsp60 in the presence of ATP, and (iii) ATP synergistically activated human HBV Pol wit h Hsp60. In vivo experiments showed that inhibition of Hsp60 in cells by a mutant Hsp60, C Delta 540, resulted in the reduction of human HBV Pol activ ity. In summary, our results indicate that the interaction is significant f or conversion of human HBV Pol into the active state.