Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P51532 (transcriptional activator)
 6,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In addition to serving a role as a DNA binding-dependent transcriptional activator, p53 has been reported to repress a variety of promoters that lack p53 binding sites. Data from recent studies have suggested that this activity is mediated via an interaction between p53 and the TATA box binding protein (TBP). To investigate the functional relevance of this interaction in vivo, we have performed transient transfection assays in Drosophila Schneider cells. Wild-type p53 was found to repress expression from TATA box- but not initiator (Inr)-containing promoters activated by GAL4-VP16, GAL4-ftzQ or Sp1. A mutant p53(His175), defective in DNA binding and transcriptional activation, also inhibited TATA-dependent transcription activated by Sp1. However, p53 was unable to repress a basal TATA promoter stimulated by overexpression of TBP. Furthermore, overexpression of TBP failed to rescue the p53-mediated repression of activated transcription and a p53 mutant with its N-terminal TBP interaction domain intact, but defective in transcriptional activation and binding to TBP-associated factors (TAFs), was similarly defective in transcriptional repression. These data suggest that a p53-TBP interaction is not sufficient for transcriptional repression by p53 and that repression involves an interaction between p53 and other factors, such as TAFs, that are required for activated but not basal transcription. We suggest that p53-mediated repression results from squelching of a factor limiting for activated transcription from TATA- but not Inr-containing promoters.
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PMID:Transcriptional repression by p53 involves molecular interactions distinct from those with the TATA box binding protein. 893 84

Activation of protein-encoding genes involves recruitment of an RNA polymerase II holoenzyme to promoters. Since the Srb4 subunit of the holoenzyme is essential for expression of most class II genes and is a target of at least one transcriptional activator, we reasoned that suppressors of a temperature-sensitive mutation in Srb4 would identify other factors generally involved in regulation of gene expression. We report here that MED6 and SRB6, both of which encode essential components of the holoenzyme, are among the dominant suppressors and that the products of these genes interact physically with Srb4. The recessive suppressors include NCB1 (BUR6), NCB2, NOT1, NOT3, NOT5, and CAF1, which encode subunits of NC2 and the Not complex. NC2 and Not proteins are general negative regulators which interact with TATA box binding protein (TBP). Taken together, these results suggest that transcription initiation involves a dynamic balance between activation mediated by specific components of the holoenzyme and repression by multiple TBP-associated regulators.
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PMID:Interplay of positive and negative regulators in transcription initiation by RNA polymerase II holoenzyme. 967 55

TFIID is a multiprotein complex consisting of the TATA box binding protein and multiple tightly associated proteins (TAFIIs) that are required for transcription by selected activators. We previously reported cloning and partial characterization of human TAFII130 (hTAFII130). The central domain of hTAFII130 contains four glutamine-rich regions, designated Q1 to Q4, that are involved in interactions with the transcriptional activator Sp1. Mutational analysis has revealed specific regions within the glutamine-rich (Q1 to Q4) central region of hTAFII130 that are required for interaction with distinct activation domains. We tested amino- and carboxyl-terminal deletions of hTAFII130 for interaction with Sp1 activation domains A and B (Sp1A and Sp1B) and the N-terminal activation domain of CREB (CREB-N) by using the yeast two-hybrid system. Our results indicate that Sp1B interacts almost exclusively with the Q1 region of hTAFII130. In contrast, Sp1A makes multiple contacts with Q1 to Q4 of hTAFII130, while CREB-N interacts primarily with the Q1-Q2 hTAFII130 subdomain. Consistent with these interaction studies, overexpression of the Q1-to-Q4 region in HeLa cells inhibits Sp1- but not VP16-mediated transcriptional activation. These findings indicate that the Q1-to-Q4 region of hTAFII130 is required for Sp1-mediated transcriptional enhancement in mammalian cells and that different activation domains target distinct subdomains of hTAFII130.
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PMID:Distinct subdomains of human TAFII130 are required for interactions with glutamine-rich transcriptional activators. 974 90

The 14-3-3 family of multifunctional proteins is highly conserved among animals, plants, and yeast. Several studies have shown that these proteins are associated with a G-box DNA binding complex and are present in the nucleus in several plant and animal species. In this study, 14-3-3 proteins are shown to bind the TATA box binding protein (TBP), transcription factor IIB (TFIIB), and the human TBP-associated factor hTAF(II)32 in vitro but not hTAF(II)55. The interactions with TBP and TFIIB were highly specific, requiring amino acid residues in the box 1 domain of the 14-3-3 protein. These interactions do not require formation of the 14-3-3 dimer and are not dependent on known 14-3-3 recognition motifs containing phosphoserine. The 14-3-3-TFIIB interaction appears to occur within the same domain of TFIIB that binds the human herpes simplex virus transcriptional activator VP16, because VP16 and 14-3-3 were able to compete for interaction with TFIIB in vitro. In a plant transient expression system, 14-3-3 was able to activate GAL4-dependent beta-glucuronidase reporter gene expression at low levels when translationally fused with the GAL4 DNA binding domain. The in vitro binding with general transcription factors TBP and TFIIB together with its nuclear location provide evidence supporting a role for 14-3-3 proteins as transcriptional activators or coactivators when part of a DNA binding complex.
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PMID:Specific interactions with TBP and TFIIB in vitro suggest that 14-3-3 proteins may participate in the regulation of transcription when part of a DNA binding complex. 1044 90

Previous work has shown that binding of the TATA box binding protein (TBP) to the TATA box is a rate-limiting step during pre-initiation complex (PIC) formation. Although the transcription of eukaryotic genes normally proceeds in one direction, studies in solution have shown that TBP lacks the information necessary to orient itself on the TATA box. Instead, yeast TBP binds TATA-containing promoters in two orientations that are related by a 180 rotation about TBP's pseudo-2-fold symmetry axis. Recruitment of PIC components by gene-specific activators is considered a primary mechanism of transcriptional enhancement. Here we ask whether activators might function, at least in part, by increasing the fraction of PICs assembled with TBP bound in the orientation necessary for transcription. We use DNA affinity cleavage and a TBP-phenanthroline-copper conjugate to monitor the orientation of TBP in the presence of the well-studied activators Gal4-VP16 and Gal4-AH. In the absence of a transcriptional activator, only 51% of the TBP x TATA box complexes were bound in the orientation necessary for the initiation of transcription. However, in the presence of saturating Gal4-VP16, 87% of the TBP bound to the TATA box was oriented correctly at equilibrium. This increase in orientational specificity corresponds to a free energy difference (Delta Delta G(obs)) of 1.1 kcal x mol(-1) and was accompanied by a dramatic increase in axial specificity, reminiscent of the effects of transcription factors TFIIB and TFIIA reported previously. Gal4-AH also enhanced the orientational and axial specificity of the TBP x TATA complex, although to a lesser extent. We suggest that these effects on specificity represent a variation of recruitment, since they require direct interactions between the activator and a PIC component but only increase the effective concentration of the correctly oriented PIC component. These findings add to increasing evidence that recruitment may encompass a broad range of mechanisms.
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PMID:Gal4-VP16 and Gal4-AH increase the orientational and axial specificity of TATA box recognition by TATA box binding protein. 1186 54

The TATA box binding protein (TBP) is the platform for assembly of archaeal and eukaryotic transcription preinitiation complexes. Ancestral gene duplication and fusion events have produced the saddle-shaped TBP molecule, with its two direct-repeat subdomains and pseudo-two-fold symmetry. Collectively, eukaryotic TBPs have diverged from their present-day archaeal counterparts, which remain highly symmetrical. The similarity of the N- and C-halves of archaeal TBPs is especially pronounced in the Methanococcales and Thermoplasmatales, including complete conservation of their N- and C-terminal stirrups; along with helix H'1, the C-terminal stirrup of TBP forms the main interface with TFB/TFIIB. Here, we show that, in stark contrast to its eukaryotic counterparts, multiple substitutions in the C-terminal stirrup of Methanocaldococcus jannaschii (Mja) TBP do not completely abrogate basal transcription. Using DNA affinity cleavage, we show that, by assembling TFB through its conserved N-terminal stirrup, Mja TBP is in effect ambidextrous with regard to basal transcription. In contrast, substitutions in either its N- or the C-terminal stirrup abrogate activated transcription in response to the Lrp-family transcriptional activator Ptr2.
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PMID:TBP domain symmetry in basal and activated archaeal transcription. 1900 15

Nucleosomes are believed to inhibit DNA binding by transcription factors. Theoretical attempts to understand the significance of nucleosomes in gene expression and regulation are based upon this assumption. However, nucleosomal inhibition of transcription factor binding to DNA is not complete. Rather, access to nucleosomal DNA depends on a number of factors, including the stereochemistry of transcription factor-DNA interaction, the in vivo kinetics of thermal fluctuations in nucleosome structure, and the intracellular concentration of the transcription factor. In vitro binding studies must therefore be complemented with in vivo measurements. The inducible PHO5 promoter of yeast has played a prominent role in this discussion. It bears two binding sites for the transcriptional activator Pho4, which at the repressed promoter are positioned within a nucleosome and in the linker region between two nucleosomes, respectively. Earlier studies suggested that the nucleosomal binding site is inaccessible to Pho4 binding in the absence of chromatin remodeling. However, this notion has been challenged by several recent reports. We therefore have reanalyzed transcription factor binding to the PHO5 promoter in vivo, using 'chromatin endogenous cleavage' (ChEC). Our results unambiguously demonstrate that nucleosomes effectively interfere with the binding of Pho4 and other critical transcription factors to regulatory sequences of the PHO5 promoter. Our data furthermore suggest that Pho4 recruits the TATA box binding protein to the PHO5 promoter.
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PMID:Occlusion of regulatory sequences by promoter nucleosomes in vivo. 2140 17