Cell Cycle-Dependent Stimulation of the HIV-1 Promoter by Tat-Associated CAK Activator

Nekhai, Sergeï; Shukla, Ram R.; Fernandez, Anne; Kumar, Ajit; Lamb, Ned

doi:10.1006/viro.1999.0035

Cited by 25 publications

(39 citation statements)

References 55 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Overexpression of specific CDK inhibitors, p16 and p27, blocked Tat transactivation (10). Overexpression of dominant negative mutants of CDK2 and CDK4 but not CDK1 blocked Tat transactivation (10). These data indicate that Tat-dependent transcription may in part be regulated by CDK2, which activity is highest at the G 1 phase.…”

Section: Discussionmentioning

confidence: 80%

“…We have observed that Tat-mediated transcription is regulated during the cell cycle (10,26). We have demonstrated that transcription from HIV-1 LTR is Tat-dependent at the G 1 and less so at G 2 /M phase of the cell cycle (26).…”

Section: Discussionmentioning

confidence: 94%

“…Microinjections of TTK into human primary fibroblasts stimulated Tat-dependent expression of a reporter LacZ gene placed under the control of HIV-1 LTR (10). It was tempting to suggest that TTK contained CDK9, but we did not find CDK9 by immunoblotting assays (10). Moreover, biochemically TTK was distinct from CDK9, because TTK phosphorylated CDK7 and promoted association of CDK7 and cyclin H (10).…”

Section: Discussionmentioning

confidence: 95%

“…We observed highest Tat response of HIV-1 LTR transcription in the cells progressing from G 0 to G 1 phase (10). Overexpression of specific CDK inhibitors, p16 and p27, blocked Tat transactivation (10). Overexpression of dominant negative mutants of CDK2 and CDK4 but not CDK1 blocked Tat transactivation (10).…”

Section: Discussionmentioning

confidence: 97%

“…We have purified a Tat-associated T-cell-derived kinase (TTK) that phosphorylates CTD (9 -11). TTK stimulates Tat transactivation in vitro (11) and in vivo (10,11). TTK containes CDK2, which phosphorylates CDK7 (11).…”

mentioning

confidence: 99%

See 4 more Smart Citations

HIV-1 Tat Interaction with RNA Polymerase II C-terminal Domain (CTD) and a Dynamic Association with CDK2 Induce CTD Phosphorylation and Transcription from HIV-1 Promoter

Deng

Ammosova

Pumfery

et al. 2002

Journal of Biological Chemistry

Self Cite

107

View full text Add to dashboard Cite

Human immunodeficiency virus, type 1 (HIV-1), Tat protein activates viral gene expression through promoting transcriptional elongation by RNA polymerase II (RNAPII). In this process Tat enhances phosphorylation of the C-terminal domain (CTD) of RNAPII by activating cell cycle-dependent kinases (CDKs) associated with general transcription factors of the promoter complex, specifically CDK7 and CDK9. We reported a Tat-associated T-cell-derived kinase, which contained CDK2. Here, we provide further evidence that CDK2 is involved in Tat HIV-11 Tat is a viral protein that interacts with transactivation response (TAR) RNA, a hairpin-loop structure at the 5Ј-end of all nascent viral transcripts (reviewed in Refs. 1 and 2). Tat stimulates transcriptional elongation (3), which is regulated by phosphorylation of the largest subunit of RNA polymerase II (RNAPII). The C-terminal domain (CTD) of RNA-PII consists of heptapeptide YSPTSPS repeats, which are phosphorylated on Ser-2 and Ser-5 residues during transcription (reviewed in Ref. 4). CTD is phosphorylated by host cell cycle-dependent protein kinases CDK7 and CDK9 (reviewed in Ref. 5). General transcription factor TFIIH-associated CDK7 phosphorylates Ser-5 during initiation of transcription, whereas positive transcription elongation factor b-associated CDK9 phosphorylates Ser-2 during elongation of transcription (5). Tat associates with the bulge of TAR RNA and also binds to cyclin T1, a cyclin partner of CDK9, which in turn interacts with the loop of TAR RNA (6). This allows CDK9/cyclin T1 to be recruited by Tat to the HIV-1 promoter (7). Tat also modifies the substrate specificity of CDK9 to achieve additional Ser-5 phosphorylation (8).Although the evidence for the role of CDK9/cyclin T1 in Tat-mediated HIV-1 transcription is overwhelming, our recent data suggest that there may be an additional CTD kinase involved in the Tat response. We have purified a Tat-associated T-cell-derived kinase (TTK) that phosphorylates CTD (9 -11). TTK stimulates Tat transactivation in vitro (11) and in vivo (10, 11). TTK containes CDK2, which phosphorylates CDK7 (11).In the work presented here, we analyze the effect of Tat on CTD phosphorylaton by CDK2/cyclin E and the function of CDK2 in transcription assays of HIV-1 promoter in vitro. Our finding demonstrated that interaction of Tat with CTD and a dynamic interaction with CDK2/cyclin E stimulated CTD phosphorylation by CDK2. Also we showed that CDK2 was part of transcription complex and was required for Tat-dependent transcription in vitro.

show abstract

Section: Discussionmentioning

confidence: 80%

Section: Discussionmentioning

confidence: 94%

Section: Discussionmentioning

confidence: 95%

Section: Discussionmentioning

confidence: 97%

mentioning

confidence: 99%

See 3 more Smart Citations

HIV-1 Tat Interaction with RNA Polymerase II C-terminal Domain (CTD) and a Dynamic Association with CDK2 Induce CTD Phosphorylation and Transcription from HIV-1 Promoter

Deng

Ammosova

Pumfery

et al. 2002

Journal of Biological Chemistry

Self Cite

107

View full text Add to dashboard Cite

show abstract

A Protein Phosphatase from Human T Cells Augments Tat Transactivation of the Human Immunodeficiency Virus Type 1 Long-Terminal Repeat

et al. 2002

View full text Add to dashboard Cite

HIV-1 Tat protein regulates viral gene expression by modulating the activity and association of cellular transcription factors with RNA polymerase II (RNAPII). Possible mechanisms include Tat-associated protein kinase(s) and phosphatase(s) that regulate phosphorylation of the C-terminal domain (CTD) of the large subunit of RNAPII. Hypophosphorylated RNAPII (RNAPIIa) is recruited to promoters during formation of a preinitiation complex, whereas hyperphosphorylated RNAPII (RNAPIIo) is associated with the elongation complex. The role of phosphatases in maintaining the equilibrium between the two phosphorylated states of RNAPII, which is required for sustained transcriptional activation from the HIV-1 LTR, is not clear. In this study, we discuss the properties of a Tat-associated CTD phosphatase fractionated from Jurkat T cells. The Tat-associated protein phosphatase (TAPP) is related to the serine/threonine, type 1, protein phosphatase (PP1) family. TAPP dephosphorylates the hyperphosphorylated form of recombinant CTD specifically on serine 2, and augments Tat-mediated transcriptional transactivation of HIV-1 LTR in an in vitro transcription reaction. TAPP is associated with the transcription complex during the early initiation steps, and its release from the HIV-1 promoter coincides with the Tat-specific activation of CDK9. The results suggest a unique role of the Tat-associated phosphatase which regulates viral transcription by target-specific dephosphorylation of RNAPII during the early stages of elongation.

show abstract

Iron Metabolism in Cancer and Infection

Nekhai

2011

Iron Physiology and Pathophysiology in Humans

Self Cite

View full text Add to dashboard Cite

Progression through the G1, S, G2, and M phases of the cell cycle is regulated by sets of Cdks bound to corresponding cyclins (reviewed in [ 1 ] ). Transition through the G1 phase is regulated by Cdk4/ cyclin D1 and by Cdk6/cyclin D3. Cdk2/cyclin E is active at the late G1 phase and is responsible for the G1/S transition. Progression through the S phase is regulated by Cdk2/cyclin A. DNA synthesis during the S phase critically relies on the enzymatic activity of ribonucleotide reductase [ 2 ] . The S/ G2 transition is regulated by Cdk1/cyclin A. Cdk1/cyclin B is responsible for the G2/M transition and for the completion of mitosis. Ribonucleotide ReductaseRibonucleotide reductase, the rate limiting enzyme for DNA synthesis and therefore critical for the S phase of the cell cycle, is composed of two subunits [ 2 ] . The R1 subunit of ribonucleotide reductase binds substrate and the R2 subunit contains nonheme iron which is important for enzymatic activity [ 2 ] . Inhibition of the enzymatic activity of R2 by iron chelators 311 and desferrioxamine inhibited growth of a number of cancer cell lines [ 3 ] . Recent studies have suggested that iron depletion infl uences the control of the cell cycle and angiogenesis and may suppress metastasis [ 4 ] .

show abstract

Cell Cycle-Dependent Stimulation of the HIV-1 Promoter by Tat-Associated CAK Activator

Cited by 25 publications

References 55 publications

HIV-1 Tat Interaction with RNA Polymerase II C-terminal Domain (CTD) and a Dynamic Association with CDK2 Induce CTD Phosphorylation and Transcription from HIV-1 Promoter

HIV-1 Tat Interaction with RNA Polymerase II C-terminal Domain (CTD) and a Dynamic Association with CDK2 Induce CTD Phosphorylation and Transcription from HIV-1 Promoter

A Protein Phosphatase from Human T Cells Augments Tat Transactivation of the Human Immunodeficiency Virus Type 1 Long-Terminal Repeat

Iron Metabolism in Cancer and Infection

Contact Info

Product

Resources

About