scholarly journals Regulation of CDK9 Activity by Phosphorylation and Dephosphorylation

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Sergei Nekhai ◽  
Michael Petukhov ◽  
Denitra Breuer
Keyword(s):  
Cell Cycle ◽  
Protein Phosphatase ◽  
Protein Phosphatase 1 ◽  
Comprehensive Review ◽  
Cyclin T1 ◽  
Typical Cell ◽  
Cdk9 Phosphorylation ◽  
Protein Components ◽  
Cycle Dependent ◽  
Hiv 1

HIV-1 transcription is regulated by CDK9/cyclin T1, which, unlike a typical cell cycle-dependent kinase, is regulated by associating with 7SK small nuclear ribonuclear protein complex (snRNP). While the protein components of this complex are well studied, the mechanism of the complex formation is still not fully understood. The association of CDK9/cyclin T1 with 7SK snRNP is, in part, regulated by a reversible CDK9 phosphorylation. Here, we present a comprehensive review of the kinases and phosphatases involved in CDK9 phosphorylation and discuss their role in regulation of HIV-1 replication and potential for being targeted for drug development. We propose a novel pathway of HIV-1 transcription regulation via CDK9 Ser-90 phosphorylation by CDK2 and CDK9 Ser-175 dephosphorylation by protein phosphatase-1.

Iron Chelation, Cell Cycle-Dependent Kinases and HIV-1 Transcription.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1550-1550
Author(s):  
Tatyana Ammosova ◽  
Zufan Debebe ◽  
Xiaomei Niu ◽  
Des R. Richardson ◽  
Marina Jerebtsova ◽  
...  
Keyword(s):  
Cell Cycle ◽  
T Cells ◽  
Rna Polymerase Ii ◽  
Iron Chelation ◽  
Iron Chelators ◽  
Intracellular Iron ◽  
Cyclin T1 ◽  
Protein Levels ◽  
Cycle Dependent ◽  
Hiv 1

Abstract Iron chelation leads to reduced cell cycle-dependent kinase 2 (CDK2) activity (reviewed in Biochim Biophys Acta2002;1603:31–46). Elongation of HIV-1 transcription is mediated by the interaction of HIV Tat with host cell cycle-dependent kinase 9 (CDK9)/cyclin T1, which phosphorylates the C-terminal domain of RNA polymerase II, and our recent studies indicate that CDK2 is also required for Tat-dependent transcription. We hypothesized that iron chelation may inhibit HIV transcription via reduced activity of cell cycle-dependent kinases. We utilized 2-hydroxy-1-naphthylaldehyde isonicotinoyl hydrazone (311; previously shown to inhibit CDK2 expression) and 4-[3,5-bis-(hydroxyphenyl) -1,2,4-triazol-1-yl]-benzoic acid (ICL670) to chelate intracellular iron. We analyzed the effect of these chelators on HIV-1 transcription using HeLa MAGI and CEM-GFP T-cells containing an integrated HIV-1 promoter and infected with adenovirus expressing HIV-1 Tat protein. Both chelators inhibited Tat-induced HIV-1 transcription, most profoundly in CEM-GFP T-cells. The chelators also inhibited one round of HIV-1 replication in CEM-T cells infected with pseudotyped HIV-1 virus. Treatment of HeLa MAGI and CEM-GFP T-cells with iron chelators decreased CDK9 protein levels and, to a lesser extent, CDK2 protein levels. Our findings provide evidence that iron chelators may inhibit HIV-1 transcription by altering expression of CDK9 and CDK2.

Iron Chelator ICL670 Inhibits HIV-1 Transcription.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 3863-3863
Author(s):  
Zufan Debebe ◽  
Tatyana Ammosova ◽  
Hanspeter Nick ◽  
Xiaomei Niu ◽  
Marina Jerebtsova ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Protein Level ◽  
Iron Chelator ◽  
Iron Chelators ◽  
Cyclin T1 ◽  
Terminal Domain ◽  
Cycle Dependent ◽  
Hiv 1

Abstract HIV-1 replication is induced by the excess of iron and iron chelation by desferrioxamine (DFO) inhibits viral replication in HIV-1 infected CEM T cells [1]. Treatment of cells with DFO or 2-hydroxy-1-naphthylaldehyde isonicotinoyl hydrazone inhibits expression of proteins that regulate cell-cycle progression, including cycle-dependent kinase 2 (CDK2) [2]. HIV-1 transcription is activated by Tat protein, which recruits transcriptional co-activators to the HIV-1 promoter. Elongation of HIV-1 transcription is mediated by the interaction of HIV Tat with host cell cycle-dependent kinase 9 (CDK9)/cyclin T1, which phosphorylates the C-terminal domain of RNA polymerase II. Our recent studies showed that CDK2 participates in HIV-1 transcription by phosphorylating Tat [3]. Thus inhibition of CDK2 by iron chelators might present a new approach to inhibit HIV-1 transcription. We evaluated the effect of a clinically approved orally effective iron chelator, 4-[3,5-bis-(hydroxyphenyl) -1,2,4-triazol-1-yl]-benzoic acid (ICL670 or deferasirox) on HIV-1 transcription. ICL670 inhibited Tat-induced HIV-1 transcription in CEM, 293T and HeLa cells at concentrations that did not induce cytotoxicity. The chelator decreased cellular activity of CDK2 but not its protein level and reduced HIV-1 Tat phosphorylation by CDK2. ICL670 did not decrease CDK9 protein level but significantly reduced association of CDK9 with cyclin T1 and reduced phosphorylation of Ser-2 residues of RNA polymerase II C-terminal domain. In conclusion, our findings add to the evidence that iron chelators may inhibit HIV-1 transcription by deregulating CDK2 and Cdk9. Further consideration should be given to the evaluation of ICL670 for future anti-retroviral therapeutics and to the development of iron chelators specifically as anti-retroviral agents.

scholarly journals Aurora B kinase and protein phosphatase 1 have opposing roles in modulating kinetochore assembly

2008 ◽  
Vol 181 (2) ◽  
pp. 241-254 ◽  
Author(s):  
Michael J. Emanuele ◽  
Weijie Lan ◽  
Miri Jwa ◽  
Stephanie A. Miller ◽  
Clarence S.M. Chan ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Protein Phosphatase ◽  
Protein Phosphatase 1 ◽  
Aurora B ◽  
Aurora B Kinase ◽  
Culture Cells ◽  
Kinetochore Assembly ◽  
M Phase ◽  
Egg Extracts ◽  
Cycle Dependent

The outer kinetochore binds microtubules to control chromosome movement. Outer kinetochore assembly is restricted to mitosis, whereas the inner kinetochore remains tethered to centromeres throughout the cell cycle. The cues that regulate this transient assembly are unknown. We find that inhibition of Aurora B kinase significantly reduces outer kinetochore assembly in Xenopus laevis and human tissue culture cells, frog egg extracts, and budding yeast. In X. leavis M phase extracts, preassembled kinetochores disassemble after inhibiting Aurora B activity with either drugs or antibodies. Kinetochore disassembly, induced by Aurora B inhibition, is rescued by restraining protein phosphatase 1 (PP1) activity. PP1 is necessary for kinetochores to disassemble at the exit from M phase, and purified enzyme is sufficient to cause disassembly on isolated mitotic nuclei. These data demonstrate that Aurora B activity is required for kinetochore maintenance and that PP1 is necessary and sufficient to disassemble kinetochores. We suggest that Aurora B and PP1 coordinate cell cycle–dependent changes in kinetochore assembly though phosphorylation of kinetochore substrates.

Hypoxia Inhibits HIV-1 Transcription.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 1305-1305
Author(s):  
Sergei Nekhai ◽  
Charles Sharroya ◽  
Tatyana Ammosova ◽  
Xiaomei Nui ◽  
Marina Jerebtsova ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Oxygen Tension ◽  
Protein Phosphatase ◽  
Tissue Oxygenation ◽  
Protein Phosphatase 1 ◽  
Tat Protein ◽  
Cyclin T1 ◽  
Hiv Transcription ◽  
Hiv 1

Abstract The hypoxic response is an important component of the body’s reaction to impaired tissue oxygenation associated with the anemia and vasoocclusive episodes of sickle cell disease (SCD). It has been reported that HIV infection progresses relatively slowly in patients with SCD (Am J Hematol1998;59:199–207). HIV-1 Tat protein promotes transcription of HIV-1 genes by inducing CDK9/cyclin T1 to phosphorylate the C-terminal domain of RNA polymerase-II. Our previous studies indicate that protein phosphatase-1 (PP1) promotes Tat-induced HIV-1 transcription (J Biol Chem2003;278:32189–941), apparently by interacting with HIV-1 Tat, for disruption of this interaction prevents induction of transcription (J Biol Chem2005;280:36364–71). Recently PP1 activity was shown to be decreased in hypoxia in part through increased association of PP1 with NIPP1 (J Cell Physiol 2006 Jul 6; Epub ahead of print). We hypothesized that decreased PP1 activity during hypoxia would reduce HIV-1 transcription and viral replication, and we have obtained experimental results consistent with this hypothesis.Increased expression of nuclear inhibitor of PP1 (NIPP1) was associated with inhibition of HIV-1 transcription and viral replication.Low oxygen tension (3%–6% O2) was associated with transient inhibition of HIV-1 transcription in transfected 293T and HeLa cells.Low oxygen tension was associated with inhibition of HIV-1 transcription in CEM T cells infected with pseudotyped HIV-1 virus. We are now planning to examine the possible role of altered PP1 activity in the observed inhibition of HIV-1 transcription during hypoxia. Thus, a clinical insight from patients with SCD has pointed the way to investigating the influence of hypoxia on HIV transcription. An improved understanding of how oxygen status influences viral activation versus inactivation might open new possibilities for treatment of hidden HIV-1 reservoirs that harbor non-replicating HIV-1 virus.

Inhibition of HIV-1 by DpT-Based Iron Chelators

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 79-79 ◽  
Author(s):  
Zufan Debebe ◽  
Krishna Kumar ◽  
Tatiana Ammosova ◽  
Xiaomei Niu ◽  
Des R Richardson ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Host Cell ◽  
Rna Polymerase Ii ◽  
Therapeutic Index ◽  
Iron Chelators ◽  
Iodide Uptake ◽  
Cyclin T1 ◽  
Cycle Dependent ◽  
Hiv 1

Abstract HIV-1 transcription is activated by HIV-1 Tat protein, which recruits transcriptional co-activators to the HIV-1 promoter. Elongation of HIV-1 transcription is mediated by the interaction of Tat with host cell cycle-dependent kinase 9 (CDK9)/cyclin T1, which phosphorylates the C-terminal domain of RNA polymerase II. Tat itself is phosphorylated by host cell cycle-dependent kinase 2 (CDK2) [1] and inhibition of CDK2 by tridentate iron chelators such as 2-hydroxy-1-naphthylaldehyde isonicotinoyl hydrazone, (311) or ICL670 (deferasirox) inhibits HIV-1 transcription [2]. In addition to the inhibition of CDK2, 311 and ICL670 also prevent association of CDK9 with cyclin T1 [2], which could lead to inhibition of CDK9 activity and also to inhibition of HIV-1 transcription. Recently, a group of novel di-2-pyridylketone thiosemicarbazone (DpT) based tridentate iron chelators were shown to exhibit marked antiproliferative activity in vivo [3]. Here we screened DpT-based and also 2-benzoylpyridine thiosemicarbazone (BpT)-based tridentate iron chelators and identified three chelators, Dp44mT, Bp4eT and Bp4aT, that inhibited HIV-1 transcription but were not cytotoxic as determined by propidium iodide uptake, LDH release and calcein-AM uptake. The inhibition of HIV-1 transcription was observed in CEM HIV-1 LTR-GFP cells infected with Adeno-Tat and in 293T cells transiently transfected with HIV-1-LTR LacZ and Tat-expressing vectors with IC50s in the mid-nanomolar range. These new iron chelators also inhibited HIV-1 replication in CEM and THP-1 cells at 10 mM concentration. Analysis of the molecular mechanism of HIV-1 inhibition revealed that the DpT- and BpT-based iron chelators inhibited the activities of both CDK9/cyclin T1 and CDK2. The CDK9/cyclin T1 complex was disrupted in the cells treated with iron chelators, suggesting a possible mechanism for the inhibition of CDK9. In conclusion, our findings provide further evidence that iron chelators may inhibit HIV-1 transcription by deregulating CDK2 and CDK9. The projected therapeutic index of the selected DpT-based iron chelators was over 103 suggesting their potential usefulness as future anti-retroviral therapeutics.

scholarly journals Cell-cycle-dependent association of protein phosphatase 1 and focal adhesion kinase

2001 ◽  
Vol 358 (2) ◽  
pp. 407 ◽  
Author(s):  
Marco FRESU ◽  
Mariarita BIANCHI ◽  
J. Thomas PARSONS ◽  
Emma VILLA-MORUZZI
Keyword(s):  
Cell Cycle ◽  
Focal Adhesion Kinase ◽  
Focal Adhesion ◽  
Protein Phosphatase ◽  
Protein Phosphatase 1 ◽  
Cycle Dependent

scholarly journals Nuclear Targeting of Protein Phosphatase-1 by HIV-1 Tat Protein

2005 ◽  
Vol 280 (43) ◽  
pp. 36364-36371 ◽  
Author(s):  
Tatyana Ammosova ◽  
Marina Jerebtsova ◽  
Monique Beullens ◽  
Bart Lesage ◽  
Angela Jackson ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Protein Phosphatase ◽  
Protein Phosphatase 1 ◽  
Tat Protein ◽  
Nuclear Targeting ◽  
Cyclin T1 ◽  
Immunodeficiency Virus ◽  
Hiv 1

Transcription of human immunodeficiency virus (HIV)-1 genes is activated by HIV-1 Tat protein, which induces phosphorylation of the C-terminal domain of RNA polymerase-II by CDK9/cyclin T1. We previously showed that Tat-induced HIV-1 transcription is regulated by protein phosphatase-1 (PP1). In the present study we demonstrate that Tat interacts with PP1 and that disruption of this interaction prevents induction of HIV-1 transcription. We show that PP1 interacts with Tat in part through the binding of Val36 and Phe38 of Tat to PP1 and that Tat is involved in the nuclear and subnuclear targeting of PP1. The PP1 binding mutant Tat-V36A/F38A displayed a decreased affinity for PP1 and was a poor activator of HIV-1 transcription. Surprisingly, Tat-Q35R mutant that had a higher affinity for PP1 was also a poor activator of HIV-1 transcription, because strong PP1 binding competed out binding of Tat to CDK9/cyclin T1. Our results suggest that Tat might function as a nuclear regulator of PP1 and that interaction of Tat with PP1 is critical for activation of HIV-1 transcription by Tat.

scholarly journals Cell cycle-dependent phosphorylation of mammalian protein phosphatase 1 by cdc2 kinase

1997 ◽  
Vol 94 (6) ◽  
pp. 2168-2173 ◽  
Author(s):  
Y.-G. Kwon ◽  
S. Y. Lee ◽  
Y. Choi ◽  
P. Greengard ◽  
A. C. Nairn
Keyword(s):  
Cell Cycle ◽  
Protein Phosphatase ◽  
Protein Phosphatase 1 ◽  
Cdc2 Kinase ◽  
Cycle Dependent ◽  
Mammalian Protein

scholarly journals Cell cycle-dependent regulation of Greatwall kinase by protein phosphatase 1 and regulatory subunit 3B

2017 ◽  
Vol 292 (24) ◽  
pp. 10026-10034 ◽  
Author(s):  
Dapeng Ren ◽  
Laura A. Fisher ◽  
Jing Zhao ◽  
Ling Wang ◽  
Byron C. Williams ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Protein Phosphatase ◽  
Protein Phosphatase 1 ◽  
Regulatory Subunit ◽  
Greatwall Kinase ◽  
Cycle Dependent
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