scholarly journals Peroxisome Proliferator-Activated Receptor γ Recruits the Positive Transcription Elongation Factor b Complex to Activate Transcription and Promote Adipogenesis

2006 ◽  
Vol 20 (7) ◽  
pp. 1494-1505 ◽  
Author(s):  
Irena Iankova ◽  
Rasmus K. Petersen ◽  
Jean-Sébastien Annicotte ◽  
Carine Chavey ◽  
Jacob B. Hansen ◽  
...  
Keyword(s):  
Transcription Elongation ◽  
Elongation Factor ◽  
Dominant Negative ◽  
Peroxisome Proliferator ◽  
Peroxisome Proliferator Activated Receptor ◽  
Factor B ◽  
Cyclin T1 ◽  
Positive Effects ◽  
Positive Transcription Elongation Factor ◽  
Transcription Elongation Factor

Abstract Positive transcription elongation factor b (P-TEFb) phosphorylates the C-terminal domain of RNA polymerase II, facilitating transcriptional elongation. In addition to its participation in general transcription, P-TEFb is recruited to specific promoters by some transcription factors such as c-Myc or MyoD. The P-TEFb complex is composed of a cyclin-dependent kinase (cdk9) subunit and a regulatory partner (cyclin T1, cyclin T2, or cyclin K). Because cdk9 has been shown to participate in differentiation processes, such as muscle cell differentiation, we studied a possible role of cdk9 in adipogenesis. In this study we show that the expression of the cdk9 p55 isoform is highly regulated during 3T3-L1 adipocyte differentiation at RNA and protein levels. Furthermore, cdk9, as well as cyclin T1 and cyclin T2, shows differences in nuclear localization at distinct stages of adipogenesis. Overexpression of cdk9 increases the adipogenic potential of 3T3-L1 cells, whereas inhibition of cdk9 by specific cdk inhibitors, and dominant-negative cdk9 mutant impairs adipogenesis. We show that the positive effects of cdk9 on the differentiation of 3T3-L1 cells are mediated by a direct interaction with and phosphorylation of peroxisome proliferator-activated receptor γ (PPARγ), which is the master regulator of this process, on the promoter of PPARγ target genes. PPARγ-cdk9 interaction results in increased transcriptional activity of PPARγ and therefore increased adipogenesis.

Abstract 535: Proteomics Analysis Identifies Positive Transcription Elongation Factor b as a Novel GATA-4-binding Partner Involved in Hypertrophic Responses in Cardiomyocytes

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Yoichi Sunagawa ◽  
Tatsuya Morimoto ◽  
Teruhisa Kawamura ◽  
Tomohide Takaya ◽  
Hiromichi Wada ◽  
...  
Keyword(s):  
Elongation Factor ◽  
Myocardial Cell ◽  
Dominant Negative ◽  
Proteomics Analysis ◽  
Factor B ◽  
Cyclin T1 ◽  
Positive Transcription Elongation Factor ◽  
Transcription Elongation Factor ◽  
Dominant Negative Form ◽  
Negative Form

Introduction: A zinc finger protein GATA-4 is one of the factors involved in transcriptional regulation during myocardial cell hypertrophy. In response to hypertrophic stimuli, GATA-4 forms a large complex with ERK, NFATc and an intrinsic histone acetyltransferase, p300. Disruption of this complex results in the inhibition of hypertrophic responses in cardiomyocytes. Hypothesis: We assessed the hypothesis that proteomics analysis may identify novel GATA-4-binding partners required for myocardial cell hypertrophy. Methods: GATA-4 was stably expressed as FLAG-HA-epitope fusion in HeLa cells by retroviral transduction. GATA-4 complex was purified from nuclear extracts of these cells by sequential immunoprecipitation with an anti-FLAG antibody followed by an anti-HA antibody (Tandem Affinity Purification). Results: By mass spectrometric analyses, we identified 73 GATA-4 binding proteins, including histone modifying factors, methyltransferase, HDAC and unknown proteins. One was cyclin-dependent kinases-9 (cdk9), a component of Positive Transcription Elongation Factor b (P-TEFb). Immunoblotting analyses demonstrated that GATA-4 formed a complex with p300, cdk9 and cyclin T1, another component of P-TEFb. A dominant-negative form of p300 disrupted the interaction of GATA-4 with cdk9 or cyclin T1. Conversely, a dominant-negative form of cdk9 and a cdk9 kinase inhibitor, 5,6-dichloro-1-h-ribofuranosyl-benzimidazole (DRB) inhibited p300-induced activation of GATA-4-dependent transcription as well as the acetylation of GATA-4. Stimulation of cardiomyocytes with phenylephrine (PE) increased the binding of GATA-4/p300 with cdk9 or cyclin T1. DN-cdk9 and DRB not only disrupted the complex of GATA-4/p300 with cdk9 or cyclin T1, but also repressed PE-induced hypertrophic responses such as myofibrillar organization, increase in cell size and promoter activation of the endothelin-1 and atrial natriuretic factors in cardiomyocytes. Conclusion: These findings demonstrate that cdk9 and cyclin T1 form a functional protein complex with GATA-4/p300 and that this large complex is a prerequisite for hypertrophic responses in cardiac myocytes.

scholarly journals Binding of Tat to TAR and Recruitment of Positive Transcription Elongation Factor b Occur Independently in Bovine Immunodeficiency Virus

2000 ◽  
Vol 74 (13) ◽  
pp. 6039-6044 ◽  
Author(s):  
Matjaz Barboric ◽  
Ran Taube ◽  
Nada Nekrep ◽  
Koh Fujinaga ◽  
B. Matija Peterlin
Keyword(s):  
Transcription Elongation ◽  
Elongation Factor ◽  
Bovine Immunodeficiency Virus ◽  
Rna Structures ◽  
Factor B ◽  
Cyclin T1 ◽  
Positive Transcription Elongation Factor ◽  
Transcription Elongation Factor ◽  
Immunodeficiency Virus ◽  
Species Specific

ABSTRACT Transcriptional transactivators (Tat) from many lentiviruses interact with their cognate transactivation response RNA structures (TAR) to increase rates of elongation rather than initiation of transcription. For several of them, the complex of Tat and a species-specific cyclin T1 must be formed before the binding to TAR can occur with high affinity and specificity. In sharp contrast, Tat from the bovine immunodeficiency virus (BIV) binds to its TAR without the help of the cyclin T1. This binding depends on the upper stem and 5′ bulge, but not the central loop in TAR. Moreover, cyclins T1 from different species can mediate effects of this Tat in cells. Unlike the situation with other lentiviruses, Tat transactivation can be rescued simply by linking a heterologous promoter to TAR in permissive cells. Thus, lentiviruses have evolved different strategies to recruit Tat and the positive transcription elongation factor b to their promoters, and interactions between Tat and TAR are independent from those between Tat and the cyclin T1 in BIV.

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