Isoquinolinesulphonamide Derivatives Inhibit Transcriptional Elongation of Human Immunodeficiency Virus Type 1 RNA in a Promyelocytic Model of Latency

Using the OM-10.1 promyelocytic model of inducible human immunodeficiency virus type 1 (HIV-1) infection, we tested a panel of known protein kinase inhibitors for an ability to block tumour necrosis factor-α-induced HIV-1 expression. Among the compounds tested, the broad-spectrum protein kinase inhibitor H-7 uniquely blocked HIV-1 expression at the level of viral transcription, but did not inhibit nuclear factor κB activation or function. In structure—activity analysis this inhibitory activity of H-7 on HIV-1 expression corresponded with the known structural requirements for the interaction of H-7 with the ATP-binding region of protein kinase C, suggesting that it was indeed related to the kinase inhibitory properties of H-7. The mechanism of H-7 transcriptional inhibition did not involve chromatin remodelling at the HIV-1 long terminal repeat promoter, as shown by nuc-1 disruption, and appeared to involve HIV-1 RNA elongation but not initiation. Therefore, H-7 and related isoquinoline-sulphonamide analogues are most likely inhibiting a kinase target essential for HIV-1 transcriptional elongation whose identity may provide new therapeutic targets for intervention.