scholarly journals Induction of TAK (Cyclin T1/P-TEFb) in Purified Resting CD4+ T Lymphocytes by Combination of Cytokines

2001 ◽  
Vol 75 (23) ◽  
pp. 11336-11343 ◽  
Author(s):  
Romi Ghose ◽  
Li-Ying Liou ◽  
Christine H. Herrmann ◽  
Andrew P. Rice
Keyword(s):  
T Lymphocytes ◽  
Rna Polymerase Ii ◽  
Interleukin 2 ◽  
Cellular Protein ◽  
Peripheral Blood Lymphocytes ◽  
Tat Protein ◽  
Necrosis Factor Alpha ◽  
Cyclin T1 ◽  
Protein Levels ◽  
Hiv 1

ABSTRACT Combinations of cytokines are known to reactivate transcription and replication of latent human immunodeficiency virus type 1 (HIV-1) proviruses in resting CD4+ T lymphocytes isolated from infected individuals. Transcription of the HIV-1 provirus by RNA polymerase II is strongly stimulated by the viral Tat protein. Tat function is mediated by a cellular protein kinase known as TAK (cyclin T1/P-TEFb) that is composed of Cdk9 and cyclin T1. We have found that treatment of peripheral blood lymphocytes and purified resting CD4+ T lymphocytes with the combination of interleukin-2 (IL-2), IL-6, and tumor necrosis factor alpha resulted in an increase in Cdk9 and cyclin T1 protein levels and an increase in TAK enzymatic activity. The cytokine induction of TAK in resting CD4+ T lymphocytes did not appear to require proliferation of lymphocytes. These results suggest that induction of TAK by cytokines secreted in the microenvironment of lymphoid tissue may be involved in the reactivation of HIV-1 in CD4+ T lymphocytes harboring a latent provirus.

scholarly journals Tat-Associated Kinase, TAK, Activity Is Regulated by Distinct Mechanisms in Peripheral Blood Lymphocytes and Promonocytic Cell Lines

1998 ◽  
Vol 72 (12) ◽  
pp. 9881-9888 ◽  
Author(s):  
Christine H. Herrmann ◽  
Richard G. Carroll ◽  
Ping Wei ◽  
Katherine A. Jones ◽  
Andrew P. Rice
Keyword(s):  
Rna Polymerase Ii ◽  
Cell Lines ◽  
Peripheral Blood ◽  
Elongation Factor ◽  
Cellular Protein ◽  
Peripheral Blood Lymphocytes ◽  
Mrna Levels ◽  
Blood Lymphocytes ◽  
Cyclin T1 ◽  
Protein Levels

ABSTRACT TAK, a multisubunit cellular protein kinase that specifically associates with the human immunodeficiency virus Tat proteins and hyperphosphorylates the carboxyl-terminal domain of RNA polymerase II, is a cofactor for Tat and mediates its transactivation function. The catalytic subunit of TAK has been identified as cyclin-dependent kinase Cdk9, and its regulatory partner has been identified as cyclin T1; these proteins are also components of positive transcription elongation factor P-TEFb. TAK activity is up-regulated upon activation of peripheral blood lymphocytes and following macrophage differentiation of promonocytic cell lines. We have found that activation of peripheral blood lymphocytes results in increased mRNA and protein levels of both Cdk9 and cyclin T1. Cdk9 and cyclin T1 induction occurred in purified CD4+ primary T cells activated by a variety of stimuli. In contrast, phorbol ester-induced differentiation of promonocytic cell lines into macrophage-like cells produced a large induction of cyclin T1 protein expression from nearly undetectable levels, while Cdk9 protein levels remained at a constant high level. Measurements of cyclin T1 mRNA levels in a promonocytic cell line suggested that regulation of cyclin T1 occurs at a posttranscriptional level. These results suggest that cyclin T1 and TAK function may be required in differentiated monocytes and further show that TAK activity can be regulated by distinct mechanisms in different cell types.

scholarly journals The AFF4 scaffold binds human P-TEFb adjacent to HIV Tat

eLife ◽  
2013 ◽  
Vol 2 ◽  
Author(s):  
Ursula Schulze-Gahmen ◽  
Heather Upton ◽  
Andrew Birnberg ◽  
Katherine Bao ◽  
Seemay Chou ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Elongation Factor ◽  
Regulatory Proteins ◽  
Tat Protein ◽  
Elongation Complex ◽  
Cyclin T1 ◽  
Subunit Interface ◽  
Hiv Tat ◽  
Gene Transcripts ◽  
Hiv 1

Human positive transcription elongation factor b (P-TEFb) phosphorylates RNA polymerase II and regulatory proteins to trigger elongation of many gene transcripts. The HIV-1 Tat protein selectively recruits P-TEFb as part of a super elongation complex (SEC) organized on a flexible AFF1 or AFF4 scaffold. To understand this specificity and determine if scaffold binding alters P-TEFb conformation, we determined the structure of a tripartite complex containing the recognition regions of P-TEFb and AFF4. AFF4 meanders over the surface of the P-TEFb cyclin T1 (CycT1) subunit but makes no stable contacts with the CDK9 kinase subunit. Interface mutations reduced CycT1 binding and AFF4-dependent transcription. AFF4 is positioned to make unexpected direct contacts with HIV Tat, and Tat enhances P-TEFb affinity for AFF4. These studies define the mechanism of scaffold recognition by P-TEFb and reveal an unanticipated intersubunit pocket on the AFF4 SEC that potentially represents a target for therapeutic intervention against HIV/AIDS.

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.

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.

RNA glycosidase and other agents target Tat to inhibit HIV-1 transcription

2018 ◽  
Vol 475 (6) ◽  
pp. 1059-1062
Author(s):  
David Harrich ◽  
Hongping Jin
Keyword(s):  
Rna Polymerase Ii ◽  
Cellular Protein ◽  
Mrna Transcription ◽  
Viral Mrnas ◽  
Cyclin T1 ◽  
Cell Functions ◽  
Acid Protein ◽  
Cellular Transcription ◽  
Hiv 1 ◽  
Amino Acid Protein

The HIV-1 tat gene encodes a small 86–104 amino acid protein depending on the HIV-1 strain. Tat is essential for HIV-1 replication through interactions with numerous cellular transcription factors. The interaction between Tat and P-TEFb, which is a cellular protein complex composed of cyclin T1 and CDK9, delivers P-TEFb to the newly transcribed viral mRNAs where phosphorylation of RNA polymerase II by CDK9 leads to highly efficient mRNA transcription. It has long been recognized that Tat is a potential anti-HIV-1 target and possibly a viral Achilles' heel. However, specifically targeting Tat without affecting normal host cell functions has been challenging. Means to inactivate Tat have been reported that includes small compounds, transdominant negative Tat proteins, and by plant-derived antivirals. Investigations of these agents have reported encouraging outcomes that inform and may hopefully affect strategies for a functional HIV-1 cure.

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 The Growth Factor Granulin Interacts with Cyclin T1 and Modulates P-TEFb-Dependent Transcription

2003 ◽  
Vol 23 (5) ◽  
pp. 1688-1702 ◽  
Author(s):  
Mainul Hoque ◽  
Tara M. Young ◽  
Chee-Gun Lee ◽  
Ginette Serrero ◽  
Michael B. Mathews ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Direct Action ◽  
Elongation Factor ◽  
Cellular Protein ◽  
Interacting Protein ◽  
Cyclin T1 ◽  
Rich Domain ◽  
Hiv 1

ABSTRACT Cyclin T1, together with the kinase CDK9, is a component of the transcription elongation factor P-TEFb which binds the human immunodeficiency virus type 1 (HIV-1) transactivator Tat. P-TEFb facilitates transcription by phosphorylating the carboxy-terminal domain (CTD) of RNA polymerase II. Cyclin T1 is an exceptionally large cyclin and is therefore a candidate for interactions with regulatory proteins. We identified granulin as a cyclin T1-interacting protein that represses expression from the HIV-1 promoter in transfected cells. The granulins, mitogenic growth factors containing repeats of a cysteine-rich motif, were reported previously to interact with Tat. We show that granulin formed stable complexes in vivo and in vitro with cyclin T1 and Tat. Granulin bound to the histidine-rich domain of cyclin T1, which was recently found to bind to the CTD, but not to cyclin T2. Binding of granulin to P-TEFb inhibited the phosphorylation of a CTD peptide. Granulin expression inhibited Tat transactivation, and tethering experiments showed that this effect was due, at least in part, to a direct action on cyclin T1 in the absence of Tat. In addition, granulin was a substrate for CDK9 but not for the other transcription-related kinases CDK7 and CDK8. Thus, granulin is a cellular protein that interacts with cyclin T1 to inhibit transcription.

scholarly journals Functional Differences between Human and Bovine Immunodeficiency Virus Tat Transcription Factors

2000 ◽  
Vol 74 (10) ◽  
pp. 4666-4671 ◽  
Author(s):  
Hal P. Bogerd ◽  
Heather L. Wiegand ◽  
Paul D. Bieniasz ◽  
Bryan R. Cullen
Keyword(s):  
Cooperative Interaction ◽  
Bovine Immunodeficiency Virus ◽  
Viral Gene ◽  
Tat Protein ◽  
Cyclin T1 ◽  
Immunodeficiency Virus ◽  
Cellular Cofactor ◽  
Ltr Promoter ◽  
Hiv 1

ABSTRACT Transcriptional transactivation of the human immunodeficiency virus type 1 (HIV-1) long terminal repeat (LTR) promoter element by the essential viral Tat protein requires recruitment of positive transcription elongation factor b (P-TEFb) to the viral TAR RNA target. The recruitment of P-TEFb, which has been proposed to be necessary and sufficient for activation of viral gene expression, is mediated by the highly cooperative interaction of Tat and cyclin T1, an essential component of P-TEFb, with the HIV-1 TAR element. Species, such as rodents, that encode cyclin T1 variants that are unable to support TAR binding by the Tat-cyclin T1 heterodimer are also unable to support HIV-1 Tat function. In contrast, we here demonstrate that the bovine immunodeficiency virus (BIV) Tat protein is fully able to bind to BIV TAR both in vivo and in vitro in the absence of any cellular cofactor. Nevertheless, BIV Tat can specifically recruit cyclin T1 to the BIV TAR element, and this recruitment is as essential for BIV Tat function as it is for HIV-1 Tat activity. However, because the cyclin T1 protein does not contribute to TAR binding, BIV Tat is able to function effectively in cells from several species that do not support HIV-1 Tat function. Thus, BIV Tat, while apparently dependent on the same cellular cofactor as the Tat proteins encoded by other lentiviruses, is nevertheless unique in terms of the mechanism used to recruit the BIV Tat-cyclin T1 complex to the viral LTR promoter.

Expression and coreceptor activity of STRL33/Bonzo on primary peripheral blood lymphocytes

Blood ◽  
2000 ◽  
Vol 96 (1) ◽  
pp. 41-49 ◽  
Author(s):  
Matthew Sharron ◽  
Stefan Pöhlmann ◽  
Ken Price ◽  
Elias Lolis ◽  
Monica Tsang ◽  
...  
Keyword(s):  
Rhesus Macaque ◽  
Expression Pattern ◽  
Peripheral Blood ◽  
Mononuclear Cells ◽  
Interleukin 2 ◽  
Peripheral Blood Lymphocytes ◽  
Blood Lymphocytes ◽  
Immunodeficiency Virus ◽  
Hiv 1

Abstract CCR5 and CXCR4 are the major coreceptors that mediate human immunodeficiency virus 1 (HIV-1) infection, while most simian immunodeficiency virus (SIV) isolates use CCR5. A number of alternative coreceptors can also mediate infection of some virus strains in vitro, although little is known about their in vivo relevance. Therefore, we characterized the expression pattern and coreceptor activity of one of these alternative coreceptors, STRL33/Bonzo, using a newly developed monoclonal antibody. In addition to being highly expressed (approximately 1000-7000 STRL33 ABS [antibody binding sites]) on specific subsets of natural killer cells (CD3−/CD16−/low/CD56+ and CD3−/CD16low/CD56−) and CD19+ B lymphocytes (approximately 300-5000 STRL33 ABS), STRL33 was expressed at levels sufficient to support virus infection on freshly isolated, truly naive CD4+/CD45RA+/CD62L+cells (6000-11 000 ABS). STRL33 expression on peripheral blood mononuclear cells (PBMCs) was increased by mitogenic stimulation (OKT3/IL-2 [interleukin-2] had a greater effect than phytohemaglutinin (PHA)/IL-2), but it was dramatically decreased upon Ficoll purification. Infection of CCR5− human peripheral blood lymphocytes (PBLs) showed that 2 different SIV envelope (Env) proteins mediated entry into STRL33+cells. More importantly, the preferential infection of STRL33+ cells in CCR5− PBLs by an R5/X4/STRL33 HIV-1 maternal isolate in the presence of a potent CXCR4 antagonist (AMD3100) suggests that STRL33 can be used as a coreceptor by HIV-1 on primary cells. Rhesus macaque (rh) STRL33 was used less efficiently than human STRL33 by the majority of SIV Env proteins tested despite similar levels of expression, thereby making it less likely that STRL33 is a relevant coreceptor in the rhesus macaque system. In summary, the expression pattern and coreceptor activity of STRL33 suggest its involvement in trafficking of tumor-infiltrating lymphocytes and indicate that STRL33 may be a relevant coreceptor in vivo.

scholarly journals A functional genetic approach suggests a novel interaction between the human immunodeficiency virus type 1 (HIV-1) Tat protein and HIV-1 TAR RNA in vivo

2003 ◽  
Vol 84 (3) ◽  
pp. 603-606 ◽  
Author(s):  
Lars H. Lund ◽  
Britta Wahren ◽  
Mariano A. Garcia-Blanco
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Tat Protein ◽  
Cyclin T1 ◽  
Immunodeficiency Virus ◽  
Tar Rna ◽  
Hiv 1

Human immunodeficiency virus type 1 (HIV-1) Tat and human Cyclin T1 form a complex and together recognize the viral TAR RNA element with specificity. Using HIV-1/equine infectious anaemia virus TAR chimeras, we show that in addition to the well-characterized interaction with the bulge, Tat recognizes the distal stem and the loop of TAR. These data support previously proposed, but unproven, molecular models.

Sign in / Sign up

Export Citation Format

Share Document