Hsp90 makes the human HBV Pol competent for in vitro priming rather than maintaining the human HBV Pol/pregenomic RNA complex

Previous studies show that the Hsp90 complex facilitates binding of duck hepatitis B virus polymerase on the epsilon stem-loop region in pregenomic RNA for the priming of Pol. In this report, we found that Hsp90 also binds to human HBV Pol and its binding seems to be involved in in vitro priming of human HBV Pol. (i) Inhibition of Hsp90 by anti-Hsp90 antibody (3G3) and (ii) the stripping of the Hsp90 by 1 M NaCl buffer containing 1% NP-40 almost completely reduced in vitro priming activity of human HBV Pol expressed in insect cells. However, binding of human HBV Pol to pregenomic RNA is different from that of duck HBV Pol. It seems that Hsp90 makes the human HBV Pol competent for in vitro priming rather than maintaining the human HBV Pol/pregenomic RNA complex as duck HBV Pol. In addition, although Hsp70 is a component of the Hsp90 complex, Hsp70 can directly bind to human HBV Pol without Hsp90.