CELLULAR TOPOISOMERASE-I ACTIVITY ASSOCIATED WITH HIV-1

Topoisomerase I activity was detected in detergent-disrupted human imm unodeficiency virus type 1 (HIV-1) particles. The enzyme did not requi re ATP for its conversion of SC DNA to an RC form, had divalent cation requirements similar to those of eukaryotic topoisomerase 1, and was significantly inhibited by the specific topoisomerase I inhibitor camp tothecin. However, camptothecin failed to inhibit replication of HIV i n infected cells at nontoxic concentrations, and an active site motif for topoisomerase I could not be detected on the HIV genome. These res ults suggests that HIV does not encode a novel topoisomerase I, but ra ther packages the cellular enzyme.