Indirubin-3'-monoxime, a derivative of a Chinese antileukemia medicine, inhibits P-TEFb function and HIV-1 replication.
OBJECTIVE
To evaluate the effects of the cyclin dependent kinase (CDK) inhibitor Indirubin-3'-monoxime (IM) on Tat-mediated transactivation function, a step of the HIV-1 cycle that is not currently targeted in antiviral therapy.


METHODS
The effects of IM on CDK implicated in HIV-1 Tat transactivation function were evaluated by kinase assays, transfection experiments, RNase protection assay and RT-PCR analysis of viral transcripts. The antiviral effect of IM was investigated in cells from HIV-1 infected individuals as well as in cell lines, primary lymphocytes and monocyte-derived macrophages. The antiviral activity of IM was also tested against drug-resistant HIV-1.


RESULTS
IM inhibits the kinase activity of CDK9 [50% inhibitory concentration (IC50) of 0.05 microM], the catalytic subunit of Positive transcription elongation factor b (P-TEFb). Inhibition of CDK9 activity by IM results in abrogation of Tat-induced expression of HIV-1 RNA in cell lines. In addition, IM inhibits the replication of HIV-1 in both peripheral blood mononuclear cells (IC50 of 1 microM) and macrophages (IC50 of 0.5 microM). IM is effective against primary and drug-resistant strains of HIV-1. Importantly, the antiviral effects of the drug were seen at concentrations that did not affect cell proliferation.


CONCLUSIONS
Non-toxic concentrations of IM inhibit HIV-1 by blocking viral gene expression mediated by the cellular factor P-TEFb. The drug is effective against wild-type and drug-resistant strains of HIV-1. IM may help control replication of HIV-1 in patients by disrupting a step of the HIV-1 cycle that is not being targeted in current antiretroviral treatments.
Heredia
Alonso
A
Institute of Human Virology, University of Maryland Biotechnology Institute, Baltimore, Maryland 21201, USA.
Davis
Charles
C
Bamba
Douty
D
Le
Nhut
N
Gwarzo
Muhammad Y
MY
Sadowska
Mariola
M
Gallo
Robert C
RC
Redfield
Robert R
RR
D018844:Cyclin-Dependent Kinases / Q000037:antagonists & inhibitors*; D004341:Drug Evaluation; D005419:Flavonoids / Q000494:pharmacology; D015497:HIV-1 / Q000502:physiology*; D006801:Humans; D007211:Indoles / Q000494:pharmacology*; D020128:Inhibitory Concentration 50; D007963:Leukocytes, Mononuclear / Q000821:virology; D008264:Macrophages / Q000821:virology; D010091:Oximes / Q000494:pharmacology*; D010880:Piperidines / Q000494:pharmacology; D042925:Positive Transcriptional Elongation Factor B / Q000037:antagonists & inhibitors*; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011687:Purines / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D000077546:Roscovitine; D020298:U937 Cells; D014779:Virus Replication / Q000187:drug effects*
D005419:Flavonoids; D007211:Indoles; D010091:Oximes; D010880:Piperidines; D047428:Protein Kinase Inhibitors; D011687:Purines; C474021:indirubin-3'-monoxime; D000077546:Roscovitine; C077990:alvocidib; D042925:Positive Transcriptional Elongation Factor B; D018844:Cyclin-Dependent Kinases