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

The yeast GAL4 protein, a transcriptional activator of genes involved in galactose metabolism, binds as a dimer to several closely related seventeen base pair upstream activation sequences (UASGs) that are nearly symmetric about a central dT-dA base pair. A previous study of a GAL4-UASG complex (Carey, M., Kakidani, H., Leatherwood, J., Mostashari, F. and Ptashne, M. (1989) J. Mol. Biol. 209, 423-432) elucidated a pattern of contacts consistent with the protein partially wrapping itself around the helical cylinder, assuming a B-form conformation for the DNA. Alternatively, both monomers could sit on one face of the cylinder if the DNA exists in an underwound conformation such as A-form. Spectroscopic studies that distinguish between these models are reported here. Oligonucleotides containing the consensus UASG or a nine base pair "half site" both exhibit circular dichroism (CD) spectra characteristic of B-form DNA. Two-dimensional NMR studies of the half-site also indicate a B-form conformation. When a GAL4 protein fragment containing the entire DNA-binding and dimerization domains (amino acids 1-140) is bound to the UASG, the CD spectrum above 240 nm changes only slightly, and not in a manner consistent with DNA unwinding. Our studies suggest that the UASG does not adopt an unusual underwound conformation in the absence or presence of the GAL4 protein, and favor the model in which the dimer partially wraps around the helix cylinder.
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PMID:Spectroscopic studies of the DNA binding site of the GAL4 "zinc finger" protein. 201 97

alcR is the pathway-specific transcriptional activator of the ethanol regulon in the filamentous fungus, Aspergillus nidulans. The deduced amino acid sequence of a cDNA clone, including the 5' part of the alcR-mRNA, shows that a putative Zn-binding domain of the all-cysteine class, exemplified by GAL4 is present. This structure presents some striking features. At variance with other structures of this class, the binding domain is strongly asymmetrical. Model building indicates that the zinc-binding motif of alcR could adopt an helix-turn-helix structure. We propose that the DNA-binding motif of alcR could participate in two types of DNA-binding structures: the zinc-cluster and the helix-turn-helix.
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PMID:Correct intron splicing generates a new type of a putative zinc-binding domain in a transcriptional activator of Aspergillus nidulans. 205 73

The transcriptional activator LAC9, a GAL4 homolog of Kluyveromyces lactis which mediates lactose and galactose-dependent activation of genes involved in the utilization of these sugars can also confer glucose repression to those genes. Here we report on the isolation and characterization of LAC9-2, an allele which encodes a glucose-sensitive activator in contrast to the one previously cloned. A single amino acid exchange of leu-104 to tryptophan is responsible for the glucose-insensitive phenotype. The mutation is located within the Zn-finger-like DNA binding domain which is highly conserved between LAC9 and GAL4. Glucose repression is also eliminated by duplication of the LAC9-2 allele. The data indicate that LAC9 is a limiting factor for beta-galactosidase gene expression under all growth conditions and that glucose reduces the activity of the activator.
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PMID:A mutation in the Zn-finger of the GAL4 homolog LAC9 results in glucose repression of its target genes. 210 31

In prokaryotes and eukaryotes many gene activators work synergistically. For example, two dimers of lambda repressor interact to promote binding of these proteins to DNA, a reaction that is crucial at the repressor concentrations found in lysogens. In this case one of the bound dimers activates transcription, evidently by touching RNA polymerase. In another example, the yeast transcriptional activator GAL4, which can stimulate transcription in many eukaryotes, binds to multiple sites on DNA to activate transcription synergistically; the presence of two such sites can elicit a level of transcription more than twice that found with a single site. In this paper we show that synergistic activation by each of several GAL4 derivatives involves a mechanism different from that illustrated by the lambda repressor: multiple activator molecules can work synergistically under conditions in which their binding sites on DNA are saturated. The accompanying paper shows that under similar conditions of activator excess, GAL4 derivatives work synergistically with a heterologous mammalian gene activator. These results support the idea that eukaryotic activators can cooperate not by directly interacting but by simultaneously touching some component(s) of the transcriptional machinery.
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PMID:A mechanism for synergistic activation of a mammalian gene by GAL4 derivatives. 216 Jun 9

In this report we study the effects of internal deletions of the yeast transcriptional activator HAP1 (CYP1) on activity at two dissimilar DNA binding sites, upstream activation sequence 1 (UAS1) of CYC1 (iso-1-cytochrome c) and CYC7 (iso-2-cytochrome c). These deletions remove up to 1061 amino acids of the 1483-residue protein and bring the carboxyl-terminal acidic activation domain closer to the amino-terminal DNA-binding domain. Surprisingly, the deletions have opposite effects at the two sites; activity at UAS1 increases with deletion size, while activity at CYC7 decreases. The mutant with the largest deletion, mini-HAP1, has no measurable activity at CYC7 but binds normally to the site in vitro. In contrast, a protein with the DNA-binding domain of HAP1 fused to the acidic activation domain of GAL4 is active at both UAS1 and CYC7. These findings are discussed in the context of two models that suggest how the DNA sequence can alter the activity of the bound HAP1. In a separate experiment, we generate a mutation in the DNA-binding domain of HAP1 that requires the addition of zinc for binding to either UAS1 or CYC7 in vitro. This finding shows that a zinc finger anchors DNA binding to both types of HAP1 sites.
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PMID:Internal deletions in the yeast transcriptional activator HAP1 have opposite effects at two sequence elements. 216 46

The carboxy-terminal 28 amino acids of the Saccharomyces cerevisiae transcriptional activator protein GAL4 execute two functions--transcriptional activation and interaction with the negative regulatory protein, GAL80. Here we demonstrate that these two functions are separable by single amino acid changes within this region. We determined the sequences of four GAL4C-mutations, and characterized the abilities of the encoded GAL4C proteins to activate transcription of the galactose/melibiose regulon in the presence of GAL80 and superrepressible GAL80S alleles. One of the GAL4C mutations can be compensated by a specific GAL80S mutation, resulting in a wild-type phenotype. These results support the idea that while the GAL4 activation function tolerates at least minor alterations in the GAL4 carboxyl terminus, the GAL80-interactive function is highly sequence-specific and sensitive even to single amino acid alterations. They also argue that the GAL80S mutations affect the affinity of GAL80 for GAL4, and not the ability of GAL80 to bind inducer.
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PMID:GAL4 mutations that separate the transcriptional activation and GAL80-interactive functions of the yeast GAL4 protein. 218 43

The promoter region of the Saccharomyces cerevisiae his3 gene contains two TATA elements, TC and TR, that direct transcription initiation to two sites designated +1 and +13. On the basis of differences between their nucleotide sequences and their responsiveness to upstream promoter elements, it has previously been proposed that TC and TR promote transcription by different molecular mechanisms. To begin a study of his3 transcription in vitro, we used S. cerevisiae nuclear extracts together with various DNA templates and transcriptional activator proteins that have been characterized in vivo. We demonstrated accurate transcription initiation in vitro at the sites used in vivo, transcriptional activation by GCN4, and activation by a GAL4 derivative on various gal-his3 hybrid promoters. In all cases, transcription stimulation was dependent on the presence of an acidic activation region in the activator protein. In addition, analysis of promoters containing a variety of TR derivatives indicated that the level of transcription in vitro was directly related to the level achieved in vivo. The results demonstrated that the in vitro system accurately reproduced all known aspects of in vivo his3 transcription that depend on the TR element. However, in striking contrast to his3 transcription in vivo, transcription in vitro yielded approximately 20 times more of the +13 transcript than the +1 transcript. This result was not due to inability of the +1 initiation site to be efficiently utilized in vitro, but rather it reflects the lack of TC function in vitro. The results support the idea that TC and TR mediate transcription from the wild-type promoter by distinct mechanisms.
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PMID:Analysis of Saccharomyces cerevisiae his3 transcription in vitro: biochemical support for multiple mechanisms of transcription. 218 1

The human c-myb proto-oncogene is the cellular progenitor of the viral v-myb oncogene and codes for a 75 kD protein involved in growth regulation and differentiation in a number of cells. Fusion proteins in which human c-myb sequences are linked to the DNA binding domain of the yeast transcriptional activator GAL4 can activate transcription from a reporter gene which carries the chloramphenicol acetyl transferase (CAT) gene linked in cis to a repeat of the GAL4 binding site. Deletions of carboxyterminal sequences allowed the identification of the domain responsible for transcriptional activation, which is located between amino acid residues 275 to 327. Deletion of this activator domain results in abrogation of the transcriptional activation. The GAL4-v-myb fusion protein can also activate transcription whereas no transactivation by GAL4-c-myb is observed, indicating that a carboxyterminal domain of c-myb which is absent from v-myb apparently negatively regulates transcriptional activation. Dimer formation which is required for transactivation by GAL4 fusion proteins can, when GAL4 is truncated, be mediated by a region of the c-myb protein upstream of the transactivator domain possibly including the transactivator domain itself but not a putative leucine zipper located downstream of this region.
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PMID:Transcriptional activation by human c-myb and v-myb genes. 218 2

The structure of the DNA binding domain of the yeast transcriptional activator GAL4 was investigated by extended X-ray fine structure (e.x.a.f.s.). Two samples of GAL4 were studied, one containing cadmium as a structural probe (Cd(II)GAL4) and the other containing the 'native' zinc (Zn(II)-GAL4). The results suggest that the structure of the DNA binding domain of GAL4 contains a two metal ion cluster distinguishing it from the 'zinc finger' proteins typified by the Xenopus laevis transcription factor TFIIIA.
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PMID:Metal ion co-ordination in the DNA binding domain of the yeast transcriptional activator GAL4. 219 36

GAL4I, GAL4II, and GAL4III are three forms of the yeast transcriptional activator protein that are readily distinguished on the basis of electrophoretic mobility during sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Phosphorylation accounts for the reduced mobility of the slowest-migrating form, GAL4III, which is found to be closely associated with high-level GAL/MEL gene expression (L. Mylin, P. Bhat, and J. Hopper, Genes Dev. 3:1157-1165, 1989). Here we show that GAL4II, like GAL4III, can be converted to GAL4I by phosphatase treatment, suggesting that in vivo GAL4II is derived from GAL4I by phosphorylation. We found that cells which overproduced GAL4 under conditions in which it drove moderate to low levels of GAL/MEL gene expression showed only forms GAL4I and GAL4II. To distinguish which forms of GAL4 (GAL4I, GAL4II, or both) might be responsible for transcription activation in the absence of GAL4III, we performed immunoblot analysis on UASgal-binding-competent GAL4 proteins from four gal4 missense mutants selected for their inability to activate transcription (M. Johnston and J. Dover, Proc. Natl. Acad. Sci. USA 84:2401-2405, 1987; Genetics 120;63-74, 1988). The three mutants with no detectable GAL1 expression did not appear to form GAL4II or GAL4III, but revertants in which GAL4-dependent transcription was restored did display GAL4II- or GAL4III-like electrophoretic species. Detection of GAL4II in a UASgal-binding mutant suggests that neither UASgal binding nor GAL/MEL gene activation is required for the formation of GAL4II. Overall, our results imply that GAL4I may be inactive in transcriptional activation, whereas GAL4II appears to be active. In light of this work, we hypothesize that phosphorylation of GAL4I makes it competent to activate transcription.
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PMID:Phosphorylated forms of GAL4 are correlated with ability to activate transcription. 220 97


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