title: Expression of a protein phosphatase 1 inhibitor, cdNIPP1, increases CDK9 threonine 186 phosphorylation and inhibits HIV-1 transcription.
abstract: CDK9/cyclin T1, a key enzyme in HIV-1 transcription, is negatively regulated by 7SK RNA and the HEXIM1 protein. Dephosphorylation of CDK9 on Thr(186) 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(35)VCF(38) 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 Thr(186) 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.
authors.affiliation: Center for Sickle Cell Disease, Howard University, Washington, DC 20001, USA.
authors.forename: Tatiana
authors.initials: T
authors.lastname: Ammosova
authors.forename: Venkat R K
authors.initials: VR
authors.lastname: Yedavalli
authors.forename: Xiaomei
authors.initials: X
authors.lastname: Niu
authors.forename: Marina
authors.initials: M
authors.lastname: Jerebtsova
authors.forename: Aleyde
authors.initials: A
authors.lastname: Van Eynde
authors.forename: Monique
authors.initials: M
authors.lastname: Beullens
authors.forename: Mathieu
authors.initials: M
authors.lastname: Bollen
authors.forename: Kuan-Teh
authors.initials: KT
authors.lastname: Jeang
authors.forename: Sergei
authors.initials: S
authors.lastname: Nekhai
mesh_terms: D000818:Animals; D019380:Anti-HIV Agents; D002460:Cell Line; D042863:Cyclin-Dependent Kinase 9 / Q000378:metabolism*; D004722:Endoribonucleases / Q000235:genetics / Q000502:physiology*; D015696:Gene Products, tat / Q000378:metabolism; D015497:HIV-1 / Q000235:genetics*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D010749:Phosphoprotein Phosphatases / Q000235:genetics / Q000502:physiology*; D010766:Phosphorylation; D054645:Protein Phosphatase 1 / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D011817:Rabbits; D013912:Threonine / Q000378:metabolism; D014158:Transcription, Genetic; D014779:Virus Replication
chemical_list: D019380:Anti-HIV Agents; D015696:Gene Products, tat; D047908:Intracellular Signaling Peptides and Proteins; D016601:RNA-Binding Proteins; C021042:protein phosphatase inhibitor-1; D013912:Threonine; D042863:Cyclin-Dependent Kinase 9; D004722:Endoribonucleases; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1; C097081:PPP1R8 protein, human