Binding site analysis of human HBV pol for molecular chaperonin, hsp60

A previous study shows that Hsp60 not only interacts with, but also activates human hepatitis B virus polymerase, HBV Pol (S. G. Park and G. Jung, 2001, J. Virol. 75, 6962-6968). To provide a more detailed analysis of the relationship between the two proteins, (i) the binding sites on human HBV Pol for Hsp60 and (ii) the effect of pregenomic RNA on human HBV Pol-Hsp60 binding were analyzed. The binding sites on human HBV Pol were mapped with several deletion mutant proteins of the Pol expressed in insect cells by using recombinant baculovirus. Immunoprecipitation of each deletion mutant protein by M2 beads showed that binding of Hsp60 to human HBV Pol requires two minimal sites on human HBV Pol: amino acids 1 to 199 (TP) and amino acids 680 to 842 (RH). Human HBV Pol was also shown to bind to Hsp60 in HepG2 cells, the host cell line for human HBV. In addition, Hsp60 binding to the Pol was found to be dispensable to pregenomic RNA binding to human HBV Pol. Overall, this article infers that Hsp60 activates human HBV Pol through binding at the TP and RH domains of the Pol and the Pol binding to Hsp60 does not require pregenomic RNA.