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, synthesized by reverse transcriptase, into a chromosome of the host cell. Integration is catalyzed by the viral integrase protein. We have previously reported that phenolic moieties in compounds such as napthoquinones, flavones, caffeic acid phenethyl ester (CAPE), and curcumin confer inhibitory activity against HIV-1 integrase. We have extended these findings by examining the effects of tyrphostins, tyrosine kinase inhibitors. The catalytic activities of HIV-1 integrase and the formation of enzyme-DNA complexes using photocross-linking were examined. Both steps of the integration reaction, 3'-processing and strand transfer, were inhibited by tyrphostins at micromolar concentrations. The DNA binding activity of integrase was inhibited at higher concentrations of tyrphostins. 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 tyrphostins, 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 experiments showing a global inhibition of the choice of attacking nucleophile in the 3'-processing reaction. None of the tyrphostins tested inhibited eukaryotic topoisomerase I, even at 100 juM, suggesting selectivity 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 families of inhibitors is discussed. Tyrphostins may provide lead compounds for development of novel antiviral agents for the treatment of acquired immunodeficiency syndrome based upon inhibition of HIV-1 integrase.