Cell cycle-dependent stimulation of the HIV-1 promoter by Tat-associated CAK activator.
Activation of the HIV-1 promoter by the virally encoded Tat protein is characterized by efficient processive transcription, mediated by host cell factors that are tethered to the promoter with the Tat-TAR RNA complex. Importantly, viral gene activation has been shown to be stimulated in mitogenically induced cells, although the link between cell cycle regulation and viral gene activation is unclear. We reported a Tat-associated CAK/CTD kinase from mitogenically induced primary human T-cells (TTK) (S. Nekhai et al., 1997, J. Virol. 71, 7436-7441). Here, biological activity of the kinase has been studied by direct microinjection at the individual-cell level. The TTK-dependent Tat response is maximal during G1 phase as shown by co-injection with Tat protein in cells synchronized at the various stages of the cell cycle. The cell cycle dependence of the Tat response was confirmed by inhibiting G0 --> G1 progression with the expression of dominant negative mutant Ras(Asn17) or the cyclin-dependent kinase CDK4. The results support a mechanism whereby transactivation of the HIV promoter is regulated by cell growth signal transduction pathways that target the Tat cofactor.
Nekhai
S
S
Department of Biochemistry, George Washington University School of Medicine, Washington, DC, 20037, USA.
Shukla
R R
RR
Fernandez
A
A
Kumar
A
A
Lamb
N J
NJ
D002453:Cell Cycle; D018797:Cell Cycle Proteins; D002460:Cell Line; D000070819:Discoidin Domain Receptor 1; D016193:G1 Phase; D015696:Gene Products, tat / Q000378:metabolism*; D015497:HIV-1 / Q000235:genetics* / Q000378:metabolism*; D006801:Humans; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic; D011494:Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D012091:Repetitive Sequences, Nucleic Acid; D015398:Signal Transduction; D015533:Transcriptional Activation; D054322:tat Gene Products, Human Immunodeficiency Virus
D018797:Cell Cycle Proteins; D015696:Gene Products, tat; D054322:tat Gene Products, Human Immunodeficiency Virus; D011494:Protein Kinases; C092030:DDR1 protein, human; D000070819:Discoidin Domain Receptor 1; D011505:Protein-Tyrosine Kinases; D020794:Receptor Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; C075840:TTK protein, human