Iron Chelation, Cell Cycle-Dependent Kinases and HIV-1 Transcription.

Abstract

Iron chelation leads to reduced cell cycle-dependent kinase 2 (CDK2) activity (reviewed in Biochim Biophys Acta 2002; 1603:31–46). Elongation of HIV-1 transcription is mediated by the interaction of HIV Tat with host cell cycle-dependent kinase 9 (CDK9)/cyclin T1, which phosphorylates the C-terminal domain of RNA polymerase II, and our recent studies indicate that CDK2 is also required for Tat-dependent transcription. We hypothesized that iron chelation may inhibit HIV transcription via reduced activity of cell cycle-dependent kinases. We utilized 2-hydroxy-1-naphthylaldehyde isonicotinoyl hydrazone (311; previously shown to inhibit CDK2 expression) and 4-[3,5-bis-(hydroxyphenyl) -1,2,4-triazol-1-yl]-benzoic acid (ICL670) to chelate intracellular iron. We analyzed the effect of these chelators on HIV-1 transcription using HeLa MAGI and CEM-GFP T-cells containing an integrated HIV-1 promoter and infected with adenovirus expressing HIV-1 Tat protein. Both chelators inhibited Tat-induced HIV-1 transcription, most profoundly in CEM-GFP T-cells. The chelators also inhibited one round of HIV-1 replication in CEM-T cells infected with pseudotyped HIV-1 virus. Treatment of HeLa MAGI and CEM-GFP T-cells with iron chelators decreased CDK9 protein levels and, to a lesser extent, CDK2 protein levels. Our findings provide evidence that iron chelators may inhibit HIV-1 transcription by altering expression of CDK9 and CDK2.