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Query: UNIPROT:P51532 (transcriptional activator)
 6,546 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The polyomavirus replication origin contains transcriptional regulatory sequences. To determine how these elements function in DNA replication, and to learn whether a common mechanism underlies the activation of transcription and DNA replication, we tested whether a well-characterized transcriptional activator, yeast GAL4, was capable of stimulating DNA replication and transcription in the same mammalian cell line. We observed that GAL4 activated polyomavirus DNA replication in mouse cells when its binding site was juxtaposed to the late border of the polyomavirus origin core. Synergistic activation of DNA replication was achieved by multimerization of the GAL4 binding site. Analysis of GAL4 mutant proteins, GAL4 hybrid proteins and mutants of the latter revealed that the activation domains of these transcriptional activators were required to stimulate DNA replication. In agreement with previously published data, the activation domains of GAL4 were also required to enhance transcription in the same mouse cell line. These observations implicate transcriptional activators in Py DNA replication and suggest that similar mechanisms govern the activation of transcription and DNA replication.
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PMID:Activation of polyomavirus DNA replication by yeast GAL4 is dependent on its transcriptional activation domains. 184 79

Ets1, the translation product of the c-ets1 proto-oncogene and the related Ets2 protein, act as sequence-specific transcriptional factors in transient transfection experiments in animal cells. We report here that in S. cerevisiae, expression of a lacZ test gene placed under the control of the GAL1 promoter is stimulated efficiently by a fusion protein in which the chicken Ets1 sequence starting from amino acid 37, is linked to the DNA binding domain of the yeast GAL4 transcriptional activator. This suggests that Ets1 contains one or more intrinsic transcription activation domain(s). However, the GAL4 integral of Ets1 fusion protein was unable to restore growth of a gal4 deletion mutant on galactose, implying that the fusion product cannot substitute for GAL4 enhancement on all GAL genes.
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PMID:Ets1, when fused to the GAL4 DNA binding domain, efficiently enhances galactose promotor dependent gene expression in yeast. 190 1

The nucleotide sequence of nirA, mediating nitrate induction in Aspergillus nidulans, has been determined. Alignment of the cDNA and the genomic DNA sequence indicates that the gene contains four introns and encodes a protein of 892 amino acids. The deduced NIRA protein displays all characteristics of a transcriptional activator. A putative double-stranded DNA-binding domain in the amino-terminal part comprises six cysteine residues, characteristic for the GAL4 family of zinc finger proteins. An amino-terminal highly acidic region and two proline-rich regions are also present. The nucleotide sequences of two mutations were determined after they were mapped by transformation with overlapping DNA fragments, amplified by the polymerase chain reaction. nirA87, a mutation conferring noninducibility by nitrate and nitrite, has a -1 frameshift at triplet 340, which eliminates 549 C-terminal amino acids from the polypeptide. Under the assumption that the truncated polypeptide is stable, it comprises the zinc finger domain and the acidic region, which seem not sufficient for transcriptional activation. nirAd-106, an allele conferring nitrogen metabolite derepression of nitrate and nitrite reductase activity, includes two transitions, changing a glutamic acid to a lysine and a valine to an alanine, situated between a basic and a proline-rich region of the protein. Northern (RNA) analysis of the wild type and of constitutive (nirAc) and derepressed (nirAd) mutants show that the nirA transcript does not vary between these strains, being in all cases constitutively expressed. On the other hand, transcript levels of structural genes (niaD and niiA) do vary, being highly inducible in the wild type but constitutively expressed in the nirAc mutant. The nirAd mutant appears phenotypically derepressed, because the niaD and niiA transcript levels are overinduced in the presence of nitrate but are still partially repressed in the presence of ammonium.
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PMID:nirA, the pathway-specific regulatory gene of nitrate assimilation in Aspergillus nidulans, encodes a putative GAL4-type zinc finger protein and contains four introns in highly conserved regions. 192 75

Glucose (catabolite) repression is mediated by multiple mechanisms that combine to regulate transcription of the GAL genes over at least a thousandfold range. We have determined that this is due predominantly to modest glucose repression (4- to 7-fold) of expression of GAL4, the gene encoding the transcriptional activator of the GAL genes. GAL4 regulation is affected by mutations in several genes previously implicated in the glucose repression pathway; it is not dependent on GAL4 or GAL80 protein function. GAL4 promoter sequences that mediate glucose repression were found to lie downstream of positively acting elements that may be "TATA boxes." Two nearly identical sequences (10/12 base pairs) in this region that may be binding sites for the MIG1 protein were identified as functional glucose-control elements. A 4-base-pair insertion in one of these sites causes constitutive GAL4 synthesis and leads to substantial relief (50-fold) of glucose repression of GAL1 expression. Furthermore, promoter deletions that modestly reduce GAL4 expression, and therefore presumably the amount of GAL4 protein synthesized, cause much greater reductions in GAL1 expression. These results suggest that GAL4 works synergistically to activate GAL1 expression. Thus, glucose repression of GAL1 expression is due largely to a relatively small reduction of GAL4 protein levels caused by reduced GAL4 transcription. This illustrates how modest regulation of a weakly expressed regulatory gene can act as a sensitive genetic switch to produce greatly amplified responses to environmental changes.
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PMID:Regulated expression of the GAL4 activator gene in yeast provides a sensitive genetic switch for glucose repression. 192 19

An in vivo selection system for isolating targets of DNA binding proteins in yeast was developed and used to identify the DNA binding site for the NGFI-B protein, a member of the steroid-thyroid hormone receptor superfamily. The feasibility of the technique was verified by selecting DNA fragments that contained binding sites for GCN4, a well-characterized yeast transcriptional activator. The DNA binding domain of NGFI-B, expressed as part of a LexA-NGFI-B-GAL4 chimeric activator, was then used to isolate a rat genomic DNA fragment that contained an NGFI-B binding site. The NGFI-B response element (NBRE) is similar to but functionally distinct from elements recognized by the estrogen and thyroid hormone receptors and the hormone receptor-like proteins COUP-TF, CF1, and H-2RIIBP. Cotransfection experiments in mammalian cells demonstrated that NGFI-B can activate transcription from the NBRE with or without its putative ligand binding domain.
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PMID:Identification of the DNA binding site for NGFI-B by genetic selection in yeast. 192 41

We describe a method that detects proteins capable of interacting with a known protein and that results in the immediate availability of the cloned genes for these interacting proteins. Plasmids are constructed to encode two hybrid proteins. One hybrid consists of the DNA-binding domain of the yeast transcriptional activator protein GAL4 fused to the known protein; the other hybrid consists of the GAL4 activation domain fused to protein sequences encoded by a library of yeast genomic DNA fragments. Interaction between the known protein and a protein encoded by one of the library plasmids leads to transcriptional activation of a reporter gene containing a binding site for GAL4. We used this method with the yeast SIR4 protein, which is involved in the transcriptional repression of yeast mating type information. (i) We used the two-hybrid system to demonstrate that SIR4 can form homodimers. (ii) A small domain consisting of the C terminus of SIR4 was shown to be sufficient to mediate this interaction. (iii) We screened a library to detect hybrid proteins that could interact with the SIR4 C-terminal domain and identified SIR4 from this library. This approach could be readily extended to mammalian proteins by the construction of appropriate cDNA libraries in the activation domain plasmid.
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PMID:The two-hybrid system: a method to identify and clone genes for proteins that interact with a protein of interest. 194 72

Genes encoding fusions between the maize regulatory protein C1 and the yeast transcriptional activator GAL4 and mutant C1 proteins were assayed for their ability to trans-activate anthocyanin biosynthetic genes in intact maize tissues. The putative DNA-binding region of C1 fused to the transcriptional activation domain of GAL4 activated transcription of anthocyanin structural gene promoters in c1 aleurones, c1 Rscm2 embryos, and c1 r embryogenic callus. Cells receiving these constructs accumulated purple anthocyanin pigments. The C1 acidic region fused to the GAL4 DNA-binding domain activated transcription of a GAL4-regulated promoter. An internal deletion of C1 also induced pigmentation; however, frameshifts in either the amino-terminal basic or carboxy-terminal acidic region blocked trans-activation, and the latter generated a dominant inhibitory protein. Fusion constructs between the wild-type C1 cDNA and the dominant inhibitor allele C1-I cDNA were used to identify the amino acid changes in C1 responsible for the C1-I inhibitory phenotype. Results from these studies establish that amino acids within the myb-homologous domain are critical for transcriptional activation.
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PMID:Identification of functional domains in the maize transcriptional activator C1: comparison of wild-type and dominant inhibitor proteins. 199 19

We previously reported that roughly 1% of the short peptides encoded by Escherichia coli genomic DNA fragments act as transcriptional activating regions in yeast when fused to GAL4(1-147), a DNA-binding portion of the yeast transcriptional activator GAL4 (ref. 1). Struhl questioned the conclusion that we had identified new transcriptional activating sequences that function in the absence of yeast transcriptional activating sequences. His criticism was based on two considerations: first, GAL4(1-147) contains an acidic segment (and subsequent experiments have shown that this region contains a weak activating region in vitro); second, attempts to isolate new activating regions failed when the DNA-binding domain of a bacterial repressor, LexA(1-87), was used as the DNA-binding unit. We report here a repeat of our original experiment using the complete LexA molecule LexA(1-202) as the DNA-binding region, instead of GAL4(1-147) or LexA(1-87). We find that, as in the original experiment, about 1% of the short peptides encoded by E. coli genomic fragments act as transcriptional activating regions when fused to intact LexA. All of the new activating regions whose sequences we determined bore an excess of acidic amino acids (see Table 1).
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PMID:Generating yeast transcriptional activators containing no yeast protein sequences. 200 81

RAP1 is a sequence-specific DNA-binding protein essential for cell growth. The occurrence of RAP1-binding sites in many promoter regions, the mating-type gene silencer elements, and telomeres suggests that RAP1 has multiple functions in the cell. To assess its role in transcription, temperature-sensitive mutations in RAP1 were generated. Analysis of rap1ts strains provides evidence that RAP1 functions in both transcriptional activation and silencing of mating-type genes. Several observations indicate that rap1ts strains are defective in the expression of MAT alpha, whose upstream activation sequence (UAS) contains a RAP1-binding site. At nonpermissive temperatures, decreases in MAT alpha steady-state transcript levels can be detected in MAT alpha rap1ts strains. Furthermore, these strains are deficient in alpha-pheromone production and simultaneously express at least two alpha-specific genes. These phenotypes can be reversed by replacing the RAP1-binding site at MAT alpha with a binding site for the GAL4 transcriptional activator. Certain rap1ts alleles have an opposite effect on the silent mating-type locus HMR, which becomes partially derepressed at nonpermissive temperatures.
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PMID:RAP1 protein activates and silences transcription of mating-type genes in yeast. 201 87

The Saccharomyces cerevisiae PUT3 gene encodes a transcriptional activator that binds to DNA sequences in the promoters of the proline utilization genes and is required for the basal and induced expression of the enzymes of this pathway. The sequence of the wild-type PUT3 gene revealed the presence of one large open reading frame capable of encoding a 979-amino-acid protein. The protein contains amino-terminal basic and cysteine-rich domains homologous to the DNA-binding motifs of other yeast transcriptional activators. Adjacent to these domains is an acidic domain with a net charge of -17. A second acidic domain with a net charge of -29 is located at the carboxy terminus. The midsection of the PUT3 protein has homology to other activators including GAL4, LAC9, PPR1, and PDR1. Mutations in PUT3 causing aberrant (either constitutive or noninducible) expression of target genes in this system have been analyzed. One activator-defective and seven activator-constitutive PUT3 alleles have been retrieved from the genome and sequenced to determine the nucleotide changes responsible for the altered function of the protein. The activator-defective mutation is a single nucleotide change within codon 409, replacing glycine with aspartic acid. One activator-constitutive mutation is a nucleotide change at codon 683, substituting phenylalanine for serine. The remaining constitutive mutations resulted in amino acid substitutions or truncations of the protein within the carboxy-terminal 76 codons. Mechanisms for regulating the activation function of the PUT3 protein are discussed.
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PMID:Analysis of constitutive and noninducible mutations of the PUT3 transcriptional activator. 201 67


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