scholarly journals Host Proteins Ku and HMGA1 As Participants of HIV-1 Transcription

Acta Naturae ◽  
2016 ◽  
Vol 8 (1) ◽  
pp. 34-47 ◽  
Author(s):  
O. A. Shadrina ◽  
E. S. Knyazhanskaya ◽  
S. P. Korolev ◽  
M. B. Gottikh
Keyword(s):  
Rna Polymerase Ii ◽  
Transcriptional Repression ◽  
Transcription Elongation ◽  
Acute Infection ◽  
Cellular Proteins ◽  
Viral Gene ◽  
Tat Protein ◽  
Host Proteins ◽  
Immunodeficiency Virus ◽  
Hiv 1

Human immunodeficiency virus type 1 is known to use the transcriptional machinery of the host cell for viral gene transcription, and the only viral protein that partakes in this process is Tat, the viral trans-activator of transcription. During acute infection, the binding of Tat to the hairpin at the beginning of the transcribed viral RNA recruits the PTEFb complex, which in turn hyperphosphorylates RNA-polymerase II and stimulates transcription elongation. Along with acute infection, HIV-1 can also lead to latent infection that is characterized by a low level of viral transcription. During the maintenance and reversal of latency, there are no detectable amounts of Tat protein in the cell and the mechanism of transcription activation in the absence of Tat protein remains unclear. The latency maintenance is also a problematic question. It seems evident that cellular proteins with a yet unknown nature or role regulate both transcriptional repression in the latent phase and its activation during transition into the lytic phase. The present review discusses the role of cellular proteins Ku and HMGA1 in the initiation of transcription elongation of the HIV-1 provirus. The review presents data regarding Ku-mediated HIV-1 transcription and its dependence on the promoter structure and the shape of viral DNA. We also describe the differential influence of the HMGA1 protein on the induced and basal transcription of HIV-1. Finally, we offer possible mechanisms for Ku and HMGA1 proteins in the proviral transcription regulation.

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.

scholarly journals Domains in the SPT5 Protein That Modulate Its Transcriptional Regulatory Properties

2000 ◽  
Vol 20 (9) ◽  
pp. 2970-2983 ◽  
Author(s):  
Dmitri Ivanov ◽  
Youn Tae Kwak ◽  
Jun Guo ◽  
Richard B. Gaynor
Keyword(s):  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Transcriptional Repression ◽  
Transcriptional Elongation ◽  
Tat Protein ◽  
C Terminus ◽  
Heptad Repeats ◽  
And Function ◽  
Hiv 1

ABSTRACT SPT5 and its binding partner SPT4 regulate transcriptional elongation by RNA polymerase II. SPT4 and SPT5 are involved in both 5,6-dichloro-1-β-d-ribofuranosylbenzimidazole (DRB)-mediated transcriptional inhibition and the activation of transcriptional elongation by the human immunodeficiency virus type 1 (HIV-1) Tat protein. Recent data suggest that P-TEFb, which is composed of CDK9 and cyclin T1, is also critical in regulating transcriptional elongation by SPT4 and SPT5. In this study, we analyze the domains of SPT5 that regulate transcriptional elongation in the presence of either DRB or the HIV-1 Tat protein. We demonstrate that SPT5 domains that bind SPT4 and RNA polymerase II, in addition to a region in the C terminus of SPT5 that contains multiple heptad repeats and is designated CTR1, are critical for in vitro transcriptional repression by DRB and activation by the Tat protein. Furthermore, the SPT5 CTR1 domain is a substrate for P-TEFb phosphorylation. These results suggest that C-terminal repeats in SPT5, like those in the RNA polymerase II C-terminal domain, are sites for P-TEFb phosphorylation and function in modulating its transcriptional elongation properties.

scholarly journals CDK13, a New Potential Human Immunodeficiency Virus Type 1 Inhibitory Factor Regulating Viral mRNA Splicing

2008 ◽  
Vol 82 (14) ◽  
pp. 7155-7166 ◽  
Author(s):  
Reem Berro ◽  
Caitlin Pedati ◽  
Kylene Kehn-Hall ◽  
Weilin Wu ◽  
Zachary Klase ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Rna Polymerase Ii ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Virus Production ◽  
Mrna Splicing ◽  
Viral Gene ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT The human immunodeficiency virus type 1 (HIV-1) Tat is a 14-kDa viral protein that acts as a potent transactivator by binding to the transactivation-responsive region, a structured RNA element located at the 5′ end of all HIV-1 transcripts. Tat transactivates viral gene expression by inducing the phosphorylation of the C-terminal domain of RNA polymerase II through several Tat-activated kinases and by recruiting chromatin-remodeling complexes and histone-modifying enzymes to the HIV-1 long terminal repeat. Histone acetyltransferases, including p300 and hGCN5, not only acetylate histones but also acetylate Tat at lysine positions 50 and 51 in the arginine-rich motif. Acetylated Tat at positions 50 and 51 interacts with a specialized protein module, the bromodomain, and recruits novel factors having this particular domain, such as P/CAF and SWI/SNF. In addition to having its effect on transcription, Tat has been shown to be involved in splicing. In this study, we demonstrate that Tat interacts with cyclin-dependent kinase 13 (CDK13) both in vivo and in vitro. We also found that CDK13 increases HIV-1 mRNA splicing and favors the production of the doubly spliced protein Nef. In addition, we demonstrate that CDK13 acts as a possible restriction factor, in that its overexpression decreases the production of the viral proteins Gag and Env and subsequently suppresses virus production. Using small interfering RNA against CDK13, we show that silencing of CDK13 leads to a significant increase in virus production. Finally, we demonstrate that CDK13 mediates its effect on splicing through the phosphorylation of ASF/SF2.

scholarly journals Arginine Methylation Increases the Stability of Human Immunodeficiency Virus Type 1 Tat

2009 ◽  
Vol 83 (22) ◽  
pp. 11694-11703 ◽  
Author(s):  
Haran Sivakumaran ◽  
Armando van der Horst ◽  
Alex J. Fulcher ◽  
Ann Apolloni ◽  
Min-Hsuan Lin ◽  
...  
Keyword(s):  
Human Immunodeficiency Virus ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Half Life ◽  
Arginine Methylation ◽  
Viral Gene ◽  
Tat Protein ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Arginine methylation of human immunodeficiency virus type 1 (HIV-1) Tat protein downregulates its key function in viral-gene transactivation. The fate of methylated Tat is unknown, so it is unclear whether methylated Tat is degraded or persists in the cell for additional functions. Here we show that the arginine methyltransferase PRMT6 increases Tat protein half-life by 4.7-fold. Tat stabilization depends on the catalytic activity of PRMT6 and requires arginine methylation within the Tat basic domain. In contrast, HIV-1 Rev, which is also methylated by PRMT6, is completely refractory to the stabilizing effect. Proteasome inhibition and silencing experiments demonstrated that Tat can be degraded by a REGγ-independent proteasome, against which PRMT6 appears to act to increase Tat half-life. Our data reveal a proteasome-dependent Tat degradation pathway that is inhibited by arginine methylation. The stabilizing action of PRMT6 could allow Tat to persist within the cell and the extracellular environment and thereby enable functions implicated in AIDS-related cancer, neurodegeneration, and T-cell death.

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 Phosphorylation of the RNA Polymerase II Carboxyl-Terminal Domain by CDK9 Is Directly Responsible for Human Immunodeficiency Virus Type 1 Tat-Activated Transcriptional Elongation

2002 ◽  
Vol 22 (13) ◽  
pp. 4622-4637 ◽  
Author(s):  
Young Kyeung Kim ◽  
Cyril F. Bourgeois ◽  
Catherine Isel ◽  
Mark J. Churcher ◽  
Jonathan Karn
Keyword(s):  
Human Immunodeficiency Virus ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Transcription Elongation ◽  
Transcriptional Elongation ◽  
Tat Protein ◽  
Immunodeficiency Virus ◽  
Carboxyl Terminal ◽  
Transcription Complexes

ABSTRACT Stimulation of transcriptional elongation by the human immunodeficiency virus type 1 Tat protein is mediated by CDK9, a kinase that phosphorylates the RNA polymerase II carboxyl-terminal domain (CTD). In order to obtain direct evidence that this phosphorylation event can alter RNA polymerase processivity, we prepared transcription elongation complexes that were arrested by the lac repressor. The CTD was then dephosphorylated by treatment with protein phosphatase 1. The dephosphorylated transcription complexes were able to resume the transcription elongation when IPTG (isopropyl-β-d-thiogalactopyranoside) and nucleotides were added to the reaction. Under these chase conditions, efficient rephosphorylation of the CTD was observed in complexes containing the Tat protein but not in transcription complexes prepared in the absence of Tat protein. Immunoblots and kinase assays with synthetic peptides showed that Tat activated CDK9 directly since the enzyme and its cyclin partner, cyclin T1, were present at equivalent levels in transcription complexes prepared in the presence or absence of Tat. Chase experiments with the dephosphorylated elongation transcription complexes were performed in the presence of the CDK9 kinase inhibitor DRB (5,6-dichloro-1-β-d-ribofuranosyl-benzimidazole). Under these conditions there was no rephosphorylation of the CTD during elongation, and transcription through either a stem-loop terminator or bent DNA arrest sequence was strongly inhibited. In experiments in which the CTD was phosphorylated prior to elongation, the amount of readthrough of the terminator sequences was proportional to the extent of the CTD modification. The change in processivity is due to CTD phosphorylation alone, since even after the removal of Spt5, the second substrate for CDK9, RNA polymerase elongation is enhanced by Tat-activated CDK9 activity. We conclude that phosphorylation of the RNA polymerase II CTD by CDK9 enhances transcription elongation directly.

scholarly journals NF-κB-Repressing Factor Inhibits Elongation of Human Immunodeficiency Virus Type 1 Transcription by DRB Sensitivity-Inducing Factor

2005 ◽  
Vol 25 (17) ◽  
pp. 7473-7483 ◽  
Author(s):  
Ursula Dreikhausen ◽  
Kirsten Hiebenthal-Millow ◽  
Myriam Bartels ◽  
Klaus Resch ◽  
Mahtab Nourbakhsh
Keyword(s):  
Human Immunodeficiency Virus ◽  
Rna Polymerase Ii ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Transcriptional Activation ◽  
Specific Binding ◽  
Transcription Elongation ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Human immunodeficiency virus type 1 (HIV-1) is able to establish a latent infection during which the integrated provirus remains transcriptionally silent. In response to specific stimuli, the HIV-1 long terminal repeat (LTR) is highly activated, enhancing both transcriptional initiation and elongation. Here, we have identified a specific binding sequence of the nuclear NF-κB-repressing factor (NRF) within the HIV-1 LTR. The aim of this work was to define the role of NRF in regulating the LTR. Our data show that the endogenous NRF is required for transcriptional activation of the HIV-1 LTR in stimulated cells. In unstimulated cells, however, NRF inhibits HIV-1 LTR activity at the level of transcription elongation. Binding of NRF to the LTR in unstimulated cells prevents recruitment of elongation factor DRB sensitivity-inducing factor and formation of processive elongation complexes by hyperphosphorylated RNA polymerase II. Our data suggest that NRF interrupts the regulatory coupling of LTR binding factors and transcription elongation events. This inhibitory mechanism might contribute to transcriptional quiescence of integrated HIV-1 provirus.

scholarly journals The Human Immunodeficiency Virus Type 1 Tat Protein Up-Regulates the Promoter Activity of the Beta-Chemokine Monocyte Chemoattractant Protein 1 in the Human Astrocytoma Cell Line U-87 MG: Role of SP-1, AP-1, and NF-κB Consensus Sites

2000 ◽  
Vol 74 (4) ◽  
pp. 1632-1640 ◽  
Author(s):  
Siew Pheng Lim ◽  
Alfredo Garzino-Demo
Keyword(s):  
Human Immunodeficiency Virus ◽  
Promoter Activity ◽  
Tat Protein ◽  
Monocyte Chemoattractant Protein 1 ◽  
Monocyte Chemoattractant ◽  
Monocyte Chemoattractant Protein ◽  
Astrocytoma Cell ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT It has been shown that the human immunodeficiency virus type 1 (HIV-1) Tat protein can specifically enhance expression and release of monocyte chemoattractant protein 1 (MCP-1) from human astrocytes. In this study, we show evidence that Tat-induced MCP-1 expression is mediated at the transcriptional level. Transient transfection of an expression construct encoding the full-length Tat into the human glioblastoma-astrocytoma cell line U-87 MG enhances reporter gene activity from cotransfected deletion constructs of the MCP-1 promoter. HIV-1 Tat exerts its effect through a minimal construct containing 213 nucleotides upstream of the translational start site. Site-directed mutagenesis studies indicate that an SP1 site (located between nucleotides −123 and −115) is critical for both constitutive and Tat-enhanced expression of the human MCP-1 promoter, as mutation of this SP1 site significantly diminished reporter gene expression in both instances. Gel retardation experiments further demonstrate that Tat strongly enhances the binding of SP1 protein to its DNA element on the MCP-1 promoter. Moreover, we also observe an increase in the binding activities of transcriptional factors AP1 and NF-κB to the MCP-1 promoter following Tat treatment. Mutagenesis studies show that an upstream AP1 site and an adjacent NF-κB site (located at −128 to −122 and −150 to −137, respectively) play a role in Tat-mediated transactivation. In contrast, a further upstream AP1 site (−156 to −150) does not appear to be crucial for promoter activity. We postulate that a Tat-mediated increase in SP1 binding activities augments the binding of AP1 and NF-κB, leading to synergistic activation of the MCP-1 promoter.

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.

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