EFFECTS OF TYRPHOSTINS, PROTEIN-KINASE INHIBITORS, ON HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 INTEGRASE

Efficient replication of HIV-1 requires establishment of the proviral state, i.e., the integration of a DNA copy of the viral genome, synthe sized by reverse transcriptase, into a chromosome of the host cell. In tegration is catalyzed by the viral integrase protein. We have previou sly reported that phenolic moieties in compounds such as napthoquinone s, flavones, caffeic acid phenethyl ester (CAPE), and curcumin confer inhibitory activity against HIV-1 integrase. We have extended these fi ndings by examining the effects of tyrphostins, tyrosine kinase inhibi tors. The catalytic activities of HIV-1 integrase and the formation of enzyme-DNA complexes using photocross-linking were examined. Both ste ps of the integration reaction, 3'-processing and strand transfer, wer e inhibited by tyrphostins at micromolar concentrations. The DNA bindi ng activity of integrase was inhibited at higher concentrations of tyr phostins. Disintegration, an apparent reversal of the strand transfer reaction, catalyzed by an integrase mutant lacking the N-terminal zinc finger and C-terminal DNA binding domains is also inhibited by tyrpho stins, indicating that the binding site for these compounds resides in the central catalytic core of HIV-1 integrase. Binding of tyrphostins at or near the integrase catalytic site was also suggested by experim ents showing a global inhibition of the choice of attacking nucleophil e in the 3'-processing reaction. None of the tyrphostins tested inhibi ted eukaryotic topoisomerase I, even at 100 mu M, suggesting selectivi ty for integrase inhibition. Molecular-modeling studies have revealed that, after energy minimization, several tyrphostins may adopt folded conformations. The similarity of the tyrphostin family to other famili es of inhibitors is discussed. Tyrphostins may provide lead compounds for development of novel antiviral agents for the treatment of acquire d immunodeficiency syndrome based upon inhibition of HIV-1 integrase.