title: Direct inhibition of CDK9 blocks HIV-1 replication without preventing T-cell activation in primary human peripheral blood lymphocytes.
abstract: HIV-1 transcription is essential for the virus replication cycle. HIV-1 Tat is a viral transactivator that strongly stimulates the processivity of RNA polymerase II (RNAPII) via recruitment of the cyclin T1/CDK9 positive transcription elongation factor, which phosphorylates the C-terminal domain (CTD) of RNAPII. Consistently, HIV-1 replication in transformed cells is very sensitive to direct CDK9 inhibition. Thus, CDK9 could be a potential target for anti-HIV-1 therapy. A clearer understanding of the requirements for CDK9 activity in primary human T cells is needed to assess whether the CDK9-dependent step in HIV-1 transcription can be targeted clinically. We have investigated the effects of limiting CDK9 activity with recombinant lentiviruses expressing a dominant-negative form of CDK9 (HA-dnCDK9) in peripheral blood lymphocytes (PBLs) and other cells. Our results show that direct inhibition of CDK9 potently inhibits HIV-1 replication in single-round infection assays with little to undetectable effects on RNAPII transcription, RNA synthesis, proliferation and viability. In PBLs purified from multiple donors, direct inhibition of CDK9 activity blocks HIV-1 replication/transcription but does not prevent T-cell activation, as determined via measurement of cell surface and cell cycle entry and progression markers, and DNA synthesis. We have also compared the effects of HA-dnCDK9 to flavopiridol (FVP), a general CDK inhibitor that potently inhibits CDK9. In contrast to HA-dnCDK9, FVP interferes with key cellular processes at concentrations that inhibit HIV-1 replication with potency similar to HA-dnCDK9. In particular, FVP inhibits several T-cell activation markers and DNA synthesis in primary PBLs at the minimal concentrations required to inhibit HIV-1 replication. Our results imply that small pharmacological compounds targeting CDK9 with enhanced selectivity could be developed into effective anti-HIV-1 therapeutic drugs.
authors.affiliation: Fels Institute for Cancer Research and Molecular Biology, Temple University School of Medicine, 3307 North Broad Street, Philadelphia, PA 19140, USA.
authors.forename: Dominic
authors.initials: D
authors.lastname: Salerno
authors.forename: Muneer G
authors.initials: MG
authors.lastname: Hasham
authors.forename: Renée
authors.initials: R
authors.lastname: Marshall
authors.forename: Judit
authors.initials: J
authors.lastname: Garriga
authors.forename: Alexander Y
authors.initials: AY
authors.lastname: Tsygankov
authors.forename: Xavier
authors.initials: X
authors.lastname: Graña
mesh_terms: D002460:Cell Line; D042863:Cyclin-Dependent Kinase 9 / Q000037:antagonists & inhibitors*; D005434:Flow Cytometry; D015497:HIV-1 / Q000235:genetics / Q000502:physiology*; D006801:Humans; D008213:Lymphocyte Activation / Q000187:drug effects*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D013601:T-Lymphocytes / Q000187:drug effects* / Q000201:enzymology; D014158:Transcription, Genetic; D014779:Virus Replication / Q000187:drug effects*
chemical_list: D047428:Protein Kinase Inhibitors; C467969:CDK9 protein, human; D042863:Cyclin-Dependent Kinase 9