The ribonuclease H activity of HIV-1 reverse transcriptase: Further biochemical characterization and search of inhibitors

Abstract

A recombinant homodimer p66/p66 of the HIV-1 reverse transcriptase (RT) was expressed in and purified from a protease-deficient strain of the yeast Saccharomyces cerevisiae. The RNase H activity associated with the homodimer was biochemically characterized. The effect of cations and the hybrid substrate specificity were studied. Some compounds which have been found to inhibit retroviral replication were tested as potential inhibitors of the retroviral DNA polymerase and RNase H activities. Most of these compounds inhibited preferentially the DNA polymerase activity. On the other hand, only suramin was found to inhibit RNase H more efficiently than DNA polymerase. As in the case of the DNA polymerase activity, the thiol-reacting agent N-ethylmaleimide (NEM) did not affect the RNAse H activity of HIV RT. When the effect of NEM was tested against E coli RNase H, a weak inhibitory effect was detected. Surprisingly, NEM strongly inhibits the same bacterial RNase H in the presence of a recombinant form of HIV RT devoid of nuclease activity. These results strongly suggest an interaction between E coli RNase H and HIV-1 RT.