Expression of a protein phosphatase 1 inhibitor, cdNIPP1, increases CDK9 threonine 186 phosphorylation and inhibits HIV-1 transcription
CDK9/cyclin T1, a key enzyme in HIV-1 transcription, is negatively regulated by 7SK RNA and the HEXIM1 protein. Dephosphorylation of CDK9 on Thr186 by protein phosphatase 1 (PP1) in stress-induced cells or by protein phosphatase M1A in normally growing cells activates CDK9. Our previous studies showed that HIV-1 Tat protein binds to PP1 through the Tat Q 35VCF38 sequence, which is similar to the PP1-binding RVXF motif and that this interaction facilitates HIV-1 transcription. In the present study, we analyzed the effect of expression of the central domain of nuclear inhibitor of PP1 (cdNIPP1) in an engineered cell line and also when cdNIPP1 was expressed as part of HIV-1 pNL4-3 in place of nef. Stable expression of cdNIPP1 increased CDK9 phosphorylation on Thr186 and the association of CDK9 with 7SK RNA. The stable expression of cdNIPP1 disrupted the interaction of Tat and PP1 and inhibited HIV-1 transcription. Expression of cdNIPP1 as a part of the HIV-1 genome inhibited HIV-1 replication. Our study provides a proof-of-concept for the future development of PP1-targeting compounds as inhibitors of HIV-1 replication.
Ammosova, Tatiana; Yedavalli, Venkat R.K.; Niu, Xiaomei; Jerebtsova, Marina; Van Eynde, Aleyde; Beullens, Monique; Bollen, Mathieu; Jeang, Kuan Teh; and Nekhai, Sergei, "Expression of a protein phosphatase 1 inhibitor, cdNIPP1, increases CDK9 threonine 186 phosphorylation and inhibits HIV-1 transcription" (2011). The Center For Sickle Cell Disease Faculty Publications. 107.