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

The Leu3 protein of Saccharomyces cerevisiae binds to specific DNA sequences present in the 5' noncoding region of at least five RNA polymerase II-transcribed genes. Leu3 functions as a transcriptional activator only when the metabolic intermediate alpha-isopropylmalate is also present. In the absence of alpha-isopropylmalate, Leu3 causes transcription to be repressed below basal levels. We show here that different portions of the Leu3 protein are responsible for activation and repression. Fusion of the 30 C-terminal residues of Leu3 to the DNA-binding domain of the Gal4 protein created a strong cross-species activator, demonstrating that the short C-terminal region is not only required but also sufficient for transcriptional activation. Using a recently developed Leu3-responsive in vitro transcription assay as a test system for repression (J. Sze, M. Woontner, J. Jaehning, and G. B. Kohlhaw, Science 258:1143-1145, 1992), we show that mutant forms of the Leu3 protein that lack the activation domain still function as repressors. The shortest repressor thus identified had only about 15% of the mass of the full-length Leu3 protein and was centered on the DNA-binding region of Leu3. Implications of this finding for the mechanism of repression are discussed.
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PMID:Transcriptional regulator Leu3 of Saccharomyces cerevisiae: separation of activator and repressor functions. 835 11

The human p53 tumor suppressor gene product can activate transcription by RNA polymerase II in the yeast, Saccharomyces cerevisiae, as well as in human cells. Several viral transcriptional activator proteins have been shown to directly contact TBP, the TATA box-binding subunit of the general initiation factor, TFIID. In this report, we use protein affinity chromatography to show that the cellular transcription factor, p53, interacts directly and specifically with yeast TBP. The TBP binding domain of p53 was localized to its N-terminal 73 amino acids. This highly acidic portion of p53 functions as a transcriptional activation domain and is deleted in some tumors induced by the Friend leukemia virus. A human tumor-derived oncogenic point mutation of p53, which lies outside the activation domain of p53, but reduces its ability to activate transcription, greatly reduced the ability of p53 to bind yeast TBP in vitro. This mutation probably affects the overall conformation of the protein and indirectly interferes with the ability of p53 to contact TBP and activate transcription. In contrast, a mutated oncogenic form of p53 that is unaffected in its ability to activate transcription bound yeast TBP as well as wild type p53. The human TBP activity in a HeLa extract also bound to the activation domain of p53. Our data support a general model in which DNA-bound activator proteins activate transcription by interacting with TBP.
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PMID:Direct interaction between the transcriptional activation domain of human p53 and the TATA box-binding protein. 842 1

A key component of the RNA polymerase II transcriptional apparatus, TFIID, is a multi-protein complex containing the TATA box-binding protein (TBP) and at least seven tightly associated factors (TAFs). Although the functions of most TFIID subunits are unknown, it is clear that TAFs are not necessary for basal activity but that one or more are required for regulated transcription, and so behave as coactivators. The presence of multiple subunits indicates that there is an intricate assembly process and that TAFs may be responsible for other activities. We have described the properties of the subunit dTAFII110, which can interact directly with the transcriptional activator Sp1 (ref. 5). In addition, the largest subunit, dTAFII250, binds directly to TBP and links other TAFs to the complex. Here we describe the cloning, expression and partial characterization of the Drosophila TAF of M(r) 80,000, dTAFII80. Sequence analysis reveals that dTAFII80 contains several copies of the WD40 (beta-transducin) repeat. Moreover, dTAFII80 shares extended sequence similarity with an Arabidopsis gene, COP1, which encodes a putative transcription factor that is though to regulate development. We have expressed recombinant dTAFII80 and begun to characterize its interaction with other members of the TFIID complex. Purified recombinant dTAFII80 is unable to bind TBP directly or to interact strongly with the C-terminal domain of dTAFII250 (delta N250). Instead, dTAFII80 is only able to recognize and interact with a higher-order complex containing TBP, delta N250, 110 and 60. These findings suggest the formation of TFIID may require an ordered assembly of the TAFs, some of which bind directly to TBP and others that are tethered to the complex as a result of specific TAF/TAF interactions.
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PMID:The dTAFII80 subunit of Drosophila TFIID contains beta-transducin repeats. 848 3

Human transcription factor TFIIB, a protein of 316 amino acids, was subjected to limited proteolysis in order to define stable structural domains. We find that the C-terminal region of TFIIB, residues 106-316, is relatively stable, while the N-terminal region is very sensitive to proteases. Like full-length TFIIB, the stable domain, which we refer to as TFIIBc, interacts with the TATA-binding protein (TBP) on DNA. However, TFIIBc is unable to substitute for TFIIB in an in vitro transcription assay. We show by gel mobility-shift experiments that TFIIBc arrests formation of the transcription complex after binding to TBP, and we conclude that the N-terminal region of TFIIB, which is missing from TFIIBc, is responsible for the recruitment of RNA polymerase II to the promoter. We also show that TFIIBc inhibits transcription by competing with full-length TFIIB for the interaction with TBP, either in the presence or in the absence of the TBP-associated factors. The acidic transcriptional activator GAL4-VP16 does not favor the assembly of the functional transcription complex over the nonfunctional complex containing TFIIBc. Thus, if the function of GAL4-VP16 is enhancement of the interaction between TFIIB and the TFIID-DNA complex, then this function can also be exerted on the protease-resistant domain TFIIBc.
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PMID:Delineation of two functional regions of transcription factor TFIIB. 851 11

NF-kappa B is a potent inducible transcription factor that regulates many genes in activated T cells. In this report we examined the ability of different subunits of NF-kappa B to enhance HIV-1 transcription in vitro with chromatin templates. We find that the p65 subunit of NF-kappa B is a strong transcriptional activator of nucleosome-assembled HIV-1 DNA, whereas p50 does not activate transcription, and that p65 activates transcription synergistically with Sp1 and distal HIV-1 enhancer-binding factors (LEF-1, Ets-1, and TFE-3). These effects were observed with chromatin, but not with nonchromatin templates. Furthermore, binding of either p50 or p65 with Sp1 induces rearrangement of the chromatin to a structure that resembles the one reported previously for integrated HIV-1 proviral DNA in vivo. These results suggest that p50 and Sp1 contribute to the establishment of the nucleosomal arrangement of the uninduced provirus in resting T cells, and that p65 activates transcription by recruitment of the RNA polymerase II transcriptional machinery to the chromatin-repressed basal promoter.
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PMID:NF-kappa B-mediated chromatin reconfiguration and transcriptional activation of the HIV-1 enhancer in vitro. 855 93

A yeast protein has been identified that stimulates basal transcription by RNA polymerase II, binds both single- and double-stranded DNA, and interacts with both a general transcription factor and a transcriptional activator. Phosphorylation appears to regulate these interactions. The gene for the transcriptional stimulatory protein, termed TSP1, was cloned and found to be dispensable for yeast cell viability. The deduced amino acid sequence is similar to that of mammalian coactivator protein PC4.
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PMID:A yeast transcriptional stimulatory protein similar to human PC4. 870 84

Contact between a transcriptional activator and one or more components of the RNA polymerase II transcription initiation machinery is generally believed important for activators to function. Several different molecular targets have been suggested for direct contact by herpes simplex virus virion protein VP16, including the general initiation factor TFIIB. In this report we have used several strategies to critically assess this interaction between VP16 and TFIIB. Affinity columns of VP16 bound TFIIB activity from HeLa cell extracts and the binding was reduced by mutations in the activation domain of VP16. In assays of direct binding, VP16 bound recombinant human TFIIB but not Drosophila or yeast TFIIB. Unlike binding from an extract, however, we found that the interaction between VP16 and recombinant human TFIIB was not affected by mutations in VP16 that reduce transactivation. Point mutations within human TFIIB that reduce transactivation by VP16 have been shown to reduce VP16 binding, but we show here that these same mutations critically affect both the important TBP-TFIIB interaction and the ability of TFIIB to support activator-independent basal transcription in vitro. Taken together our results suggest more evidence is needed to support the notion that TFIIB is a functionally important target for the activator VP16.
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PMID:Characterization of the interaction between the acidic activation domain of VP16 and the RNA polymerase II initiation factor TFIIB. 871 May 3

Previously, we showed that the viral transactivator proteins E1A and VP16 specifically interact with a cellular CTD kinase activity in vitro. We now report that E1A and VP16 complexes contain human CDK8, a newly identified member of the cyclin-dependent kinase family that has been shown to be a component of the RNA polymerase II (RNAP II) holoenzyme complex. The presence of CDK8 in the E1A- and VP16-containing complexes is specific for a functional activation domain of these viral transactivators, strongly suggesting that this association is relevant for the transactivation function of E1A and VP16. We show that CDK8 is associated with CTD kinase activity and that CDK8 co-fractionates with E1A- and VP16-associated CTD kinase activity over several chromatography columns. Therefore, CDK8 is likely responsible for the E1A- and VP16-associated CTD kinase activity. Gel filtration chromatography indicates that the E1A- and VP16-associated CTD kinase activity has a molecular size of approximately 1.5 MDa and contains cyclin C and the human homolog of SRB7 in addition to CDK8. This implies that E1A and VP16 associate with the RNAP II holoenyzme. We also looked at the transcriptional activity of CDK8 and found that CDK8 can function as a transcriptional activator when fused to the DNA binding domain of GAL4. Surprisingly, the ability of GAL4-CDK8 to activate transcription in this assay was not dependent on the kinase activity of CDK8, since a kinase-deficient mutant of CDK8 stimulated transcription nearly as well as wild-type GAL4-CDK8. This suggests that CDK8 may play a role in transcription that is distinct from its ability to function as a CTD kinase.
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PMID:Viral transactivators E1A and VP16 interact with a large complex that is associated with CTD kinase activity and contains CDK8. 887 57

Staf is a zinc finger protein that we recently identified as the transcriptional activator of the RNA polymerase III-transcribed selenocysteine tRNA gene. In this work we demonstrate that enhanced transcription of the majority of vertebrate snRNA and snRNA-type genes, transcribed by RNA polymerases II and III, also requires Staf. DNA binding assays and microinjection of mutant genes into Xenopus oocytes showed the presence of Staf-responsive elements in the genes for human U4C, U6, Y4 and 7SK, Xenopus U1b1, U2, U5 and MRP and mouse U6 RNAs. Using recombinant Staf, we established that it mediates the activating properties of Staf-responsive elements on RNA polymerase II and III snRNA promoters in vivo. Lastly a 19 bp consensus sequence for the Staf binding site, YY(A/T)CCC(A/G)N(A/C)AT(G/C)C(A/C)YY-RCR, was derived by binding site selection. It enabled us to identify 23 other snRNA and snRNA-type genes carrying potential Staf binding sites. Altogether, our results emphasize the prime importance of Staf as a novel activator for enhanced transcription of snRNA and snRNA-type genes.
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PMID:Staf, a promiscuous activator for enhanced transcription by RNA polymerases II and III. 900 78

The yeast repressor Rme1p acts from distant binding sites to block transcription of the chromosomal IME1 gene. Rme1p can also repress the heterologous CYC1 promoter when Rme1p binding sites are placed 250-300 bp upstream of CYC1 transcriptional activator binding sites (UAS1 and UAS2). Here, in vivo footprinting studies indicate that Rme1p acts over this distance by preventing the binding of the CYC1 transcriptional activators to UAS1 and UAS2. Inhibition of activator binding by Rme1p has the same genetic requirements as repression: both depend upon sequences flanking the Rme1p binding sites and upon Rgr1p and Sin4p, two subunits of the RNA polymerase II-associated Mediator complex that are required for normal nucleosome density. Thus Rme1p may alter chromatin to prevent binding of transcriptional activators to distant DNA sequences.
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PMID:Transcriptional repression at a distance through exclusion of activator binding in vivo. 902 35


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