scholarly journals Human immunodeficiency virus type 1 and 2 Tat proteins specifically interact with RNA polymerase II.

1996 ◽  
Vol 93 (5) ◽  
pp. 2089-2094 ◽  
Author(s):  
G. Mavankal ◽  
S. H. Ignatius Ou ◽  
H. Oliver ◽  
D. Sigman ◽  
R. B. Gaynor
Keyword(s):  
Human Immunodeficiency Virus ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Immunodeficiency Virus

scholarly journals Spt5 Cooperates with Human Immunodeficiency Virus Type 1 Tat by Preventing Premature RNA Release at Terminator Sequences

2002 ◽  
Vol 22 (4) ◽  
pp. 1079-1093 ◽  
Author(s):  
Cyril F. Bourgeois ◽  
Young Kyeung Kim ◽  
Mark J. Churcher ◽  
Michelle J. West ◽  
Jonathan Karn
Keyword(s):  
Human Immunodeficiency Virus ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Dna Sequences ◽  
Transcription Elongation ◽  
Elongation Factor ◽  
Immunodeficiency Virus

ABSTRACT The human immunodeficiency virus type 1 (HIV-1) Tat protein activates transcription elongation by stimulating the Tat-activated kinase (TAK/p-TEFb), a protein kinase composed of CDK9 and its cyclin partner, cyclin T1. CDK9 is able to hyperphosphorylate the carboxyl-terminal domain (CTD) of the large subunit of RNA polymerase during elongation. In addition to TAK, the transcription elongation factor Spt5 is required for the efficient activation of transcriptional elongation by Tat. To study the role of Spt5 in HIV transcription in more detail, we have developed a three-stage Tat-dependent transcription assay that permits the isolation of active preinitiation complexes, early-stage elongation complexes, and Tat-activated elongation complexes. Spt5 is recruited in the transcription complex shortly after initiation. After recruitment of Tat during elongation through the transactivation response element RNA, CDK9 is activated and induces hyperphosphorylation of Spt5 in parallel to the hyperphosphorylation of the CTD of RNA polymerase II. However, immunodepletion experiments demonstrate that Spt5 is not required for Tat-dependent activation of the kinase. Chase experiments using the Spt5-depleted extracts demonstrate that Spt5 is not required for early elongation. However, Spt5 plays an important role in late elongation by preventing the premature dissociation of RNA from the transcription complex at terminator sequences and reducing the amount of polymerase pausing at arrest sites, including bent DNA sequences. This novel biochemical function of Spt5 is analogous to the function of NusG, an elongation factor found in Escherichia coli that enhances RNA polymerase stability on templates and shows sequence similarity to Spt5.

scholarly journals A Human Immunodeficiency Virus Type 1 Tat-Like Arginine-Rich RNA-Binding Domain Is Essential for HEXIM1 To Inhibit RNA Polymerase II Transcription through 7SK snRNA-Mediated Inactivation of P-TEFb

2004 ◽  
Vol 24 (12) ◽  
pp. 5094-5105 ◽  
Author(s):  
Jasper H. N. Yik ◽  
Ruichuan Chen ◽  
Andrea C. Pezda ◽  
Craig S. Samford ◽  
Qiang Zhou
Keyword(s):  
Human Immunodeficiency Virus ◽  
Rna Polymerase ◽  
Rna Polymerase Ii ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Rna Binding ◽  
Binding Motif ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT The HEXIM1 protein inhibits the kinase activity of P-TEFb (CDK9/cyclin T) to suppress RNA polymerase II transcriptional elongation in a process that specifically requires the 7SK snRNA, which mediates the interaction of HEXIM1 with P-TEFb. In an attempt to define the sequence requirements for HEXIM1 to interact with 7SK and inactivate P-TEFb, we have identified the first 18 amino acids within the previously described nuclear localization signal (NLS) of HEXIM1 as both necessary and sufficient for binding to 7SK in vivo and in vitro. This 7SK-binding motif was essential for HEXIM1's inhibitory action, as the HEXIM1 mutants with this motif replaced with a foreign NLS failed to interact with 7SK and P-TEFb and hence were unable to inactivate P-TEFb. The 7SK-binding motif alone, however, was not sufficient to inhibit P-TEFb. A region C-terminal to this motif was also required for HEXIM1 to associate with P-TEFb and suppress P-TEFb's kinase and transcriptional activities. The 7SK-binding motif in HEXIM1 contains clusters of positively charged residues reminiscent of the arginine-rich RNA-binding motif found in a wide variety of proteins. Part of it is highly homologous to the TAR RNA-binding motif in the human immunodeficiency virus type 1 (HIV-1) Tat protein, which was able to restore the 7SK-binding ability of a HEXIM1 NLS substitution mutant. We propose that a similar RNA-protein recognition mechanism may exist to regulate the formation of both the Tat-TAR-P-TEFb and the HEXIM1-7SK-P-TEFb ternary complexes, which may help convert the inactive HEXIM1/7SK-bound P-TEFb into an active one for Tat-activated and TAR-dependent HIV-1 transcription.

scholarly journals c-Myc and Sp1 Contribute to Proviral Latency by Recruiting Histone Deacetylase 1 to the Human Immunodeficiency Virus Type 1 Promoter

2007 ◽  
Vol 81 (20) ◽  
pp. 10914-10923 ◽  
Author(s):  
Guochun Jiang ◽  
Amy Espeseth ◽  
Daria J. Hazuda ◽  
David M. Margolis
Keyword(s):  
Human Immunodeficiency Virus ◽  
Rna Polymerase Ii ◽  
Histone Deacetylase ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Molecular Mechanisms ◽  
Histone Deacetylase 1 ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Histone deacetylase (HDAC) inhibitors such as valproic acid (VPA) induce the expression of quiescent proviral human immunodeficiency virus type 1 (HIV-1) and may deplete proviral infection in vivo. To uncover novel molecular mechanisms that maintain HIV latency, we sought cellular mRNAs whose expression was diminished in resting CD4+ T cells of HIV-1-infected patients exposed to VPA. c-Myc was prominent among genes markedly downregulated upon exposure to VPA. c-Myc expression repressed HIV-1 expression in chronically infected cell lines. Chromatin immunoprecipitation (ChIP) assays revealed that c-Myc and HDAC1 are coordinately resident at the HIV-1 long terminal repeat (LTR) promoter and absent from the promoter after VPA treatment in concert with histone acetylation, RNA polymerase II recruitment, and LTR expression. Sequential ChIP assays demonstrated that c-Myc, Sp1, and HDAC1 coexist in the same DNA-protein complex at the HIV promoter. Short hairpin RNA inhibition of c-Myc reduces both c-Myc and HDAC1 occupancy, blocks c-Myc repression of Tat activation, and increases LTR expression. These results expand the understanding of mechanisms that recruit HDAC and maintain the latency of HIV-1, suggesting novel therapeutic approaches against latent proviral HIV infection.

scholarly journals Transient Induction of Cyclin T1 during Human Macrophage Differentiation Regulates Human Immunodeficiency Virus Type 1 Tat Transactivation Function

2002 ◽  
Vol 76 (21) ◽  
pp. 10579-10587 ◽  
Author(s):  
Li-Ying Liou ◽  
Christine H. Herrmann ◽  
Andrew P. Rice
Keyword(s):  
Human Immunodeficiency Virus ◽  
Protein Expression ◽  
Rna Polymerase Ii ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Human Macrophage ◽  
Macrophage Differentiation ◽  
Cyclin T1 ◽  
Immunodeficiency Virus

ABSTRACT The human immunodeficiency virus type 1 (HIV-1) Tat protein is essential for viral replication and stimulates transcription of the integrated provirus by recruiting the kinase complex TAK/P-TEFb, composed of cyclin T1 (CycT1) and Cdk9, to the viral TAR RNA element. TAK/P-TEFb phosphorylates the RNA polymerase II complex and stimulates transcriptional elongation. In this report, we investigated the regulation of TAK/P-TEFb in primary human macrophages, a major target cell of HIV infection. While Cdk9 levels remained constant, CycT1 protein expression in freshly isolated monocytes was very low, increased early during macrophage differentiation, and, unexpectedly, decreased to very low levels after about 1 week in culture. The kinase activity of TAK/P-TEFb paralleled the changes in CycT1 protein expression. RNA analysis indicated that the transient induction of CycT1 protein expression involves a posttranscriptional mechanism. In transient transfection assays, the ability of Tat to transactivate the HIV long terminal repeat (LTR) in the late differentiated macrophages was greatly diminished relative to its ability to transactivate the HIV LTR in early differentiated cells, strongly suggesting that CycT1 is limiting for Tat function in late differentiated macrophages. Interestingly, lipopolysaccharide, a component of the cell wall of gram-negative bacteria, reinduced CycT1 expression late in macrophage differentiation. These results raise the possibility that regulation of CycT1 expression may be involved in establishing latent infection in macrophages and that opportunistic infection may reactivate the virus by inducing CycT1 expression.

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 Tat Activates Human Immunodeficiency Virus Type 1 Transcriptional Elongation Independent of TFIIH Kinase

1999 ◽  
Vol 19 (4) ◽  
pp. 2863-2871 ◽  
Author(s):  
Dan Chen ◽  
Qiang Zhou
Keyword(s):  
Human Immunodeficiency Virus ◽  
Rna Polymerase Ii ◽  
Human Immunodeficiency Virus Type ◽  
Virus Type ◽  
Kinase Activity ◽  
Transcriptional Elongation ◽  
Transactivation Domain ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT Tat stimulates human immunodeficiency virus type 1 (HIV-1) transcriptional elongation by recruitment of the human transcription elongation factor P-TEFb, consisting of Cdk9 and cyclin T1, to the HIV-1 promoter via cooperative binding to the nascent HIV-1 transactivation response RNA element. The Cdk9 kinase activity has been shown to be essential for P-TEFb to hyperphosphorylate the carboxy-terminal domain (CTD) of RNA polymerase II and mediate Tat transactivation. Recent reports have shown that Tat can also interact with the multisubunit transcription factor TFIIH complex and increase the phosphorylation of CTD by the Cdk-activating kinase (CAK) complex associated with the core TFIIH. These observations have led to the proposal that TFIIH and P-TEFb may act sequentially and in a concerted manner to promote phosphorylation of CTD and increase polymerase processivity. Here, we show that under conditions in which a specific and efficient interaction between Tat and P-TEFb is observed, only a weak interaction between Tat and TFIIH that is independent of critical amino acid residues in the Tat transactivation domain can be detected. Furthermore, immunodepletion of CAK under high-salt conditions, which allow CAK to be dissociated from core-TFIIH, has no effect on either basal HIV-1 transcription or Tat activation of polymerase elongation in vitro. Therefore, unlike the P-TEFb kinase activity that is essential for Tat activation of HIV-1 transcriptional elongation, the CAK kinase associated with TFIIH appears to be dispensable for Tat function.

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