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)

Bacterial resistance to mercuric compounds is controlled by the MerR metalloregulatory protein. The MerR protein functions as both a transcriptional repressor and a mercuric ion dependent transcriptional activator. Chemical mutagenesis of the cloned merR structural gene has led to the identification of mutant proteins that are specifically deficient in transcriptional repression, activation, or both. Five mutant proteins have been overproduced, purified to homogeneity, and assayed for ability to dimerize, bind mer operator DNA, and bind mercuric ion. A mutation in the recognition helix of a proposed helix-turn-helix DNA binding motif (E22K) yields protein deficient in both activation and repression in vivo (a-r-) and deficient in operator binding in vitro. In contrast, mutations in three of the four MerR cysteine residues are repression competent but activation deficient (a-r+) in vivo. In vitro, the purified cysteine mutant proteins bind to the mer operator site with near wild-type affinity but are variably deficient in binding the in vivo inducer mercury(II) ion. A subset of the isolated proteins also appears compromised in their ability to form dimers at low protein concentrations. These data, taken with the results in the preceding paper (Shewchuk et al., 1989), support a model in which DNA-bound MerR dimer binds one mercuric ion and transmits this occupancy information to a protein region involved in transcriptional activation.
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PMID:Transcriptional switching by the MerR protein: activation and repression mutants implicate distinct DNA and mercury(II) binding domains. 249 78

CUP2 is a regulatory gene controlling expression of CUP1, which encodes the Cu-binding yeast metallothionein. CUP2, which is identical to the ACE1 gene, encodes a Cu-regulated DNA-binding protein. The CUP2 protein contains a cysteine-rich DNA-binding domain dependent on Cu+ and Ag+ ions which bind the cysteine residues and direct the refolding of the metal-free apoprotein. CUP2 mutant alleles from Cu-sensitive yeast strains have point mutations affecting the DNA-binding activity. These results establish CUP2 as the primary sensor of intracellular Cu+ in the yeast Saccharomyces cerevisiae, functioning as a Cu+-regulated transcriptional activator.
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PMID:The CUP2 gene product, regulator of yeast metallothionein expression, is a copper-activated DNA-binding protein. 267 88

We have shown previously that a synthetic peptide of 49 amino acids, encoding mainly adenovirus E1A protein domain 3 (PD3), functions as an autonomous transcriptional activator. Here we provide two lines of evidence showing that E1A transactivation does not require the induction of cellular protein synthesis. First, PD3 rapidly transactivates E1A-inducible early viral genes in the presence of inhibitors of protein synthesis, as demonstrated by microinjection-in situ hybridization experiments. Second, PD3 greatly stimulates transcription of E1A-inducible genes in vitro. Mutant PD3 peptides with single amino acid substitutions in conserved cysteine residues are defective in transactivation both in vivo and in vitro. Our findings provide compelling evidence that protein synthesis is not required for E1A transactivation, and support a model in which E1A modifies the activity of a preexisting cellular protein(s) involved in the regulation of transcription.
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PMID:An adenovirus E1A protein domain activates transcription in vivo and in vitro in the absence of protein synthesis. 296 58

The E. coli ada gene positively controls its own expression and that of other genes (alkA, alkB, aidB) involved in repair of DNA alkylation damage. The cloned ada and alkA genes and purified Ada protein have been used in cell-free systems to identify the inducing signal. Self-methylation of the Ada protein by transfer of a methyl group from a phosphotriester in alkylated DNA to a cysteine residue in the protein converts it to an activator of transcription. The covalently modified Ada protein binds specifically to promoter regions containing the sequence d(AAANNAAAGCGCA) immediately upstream of the RNA polymerase binding sites. This is apparently the first example of conversion of a regulatory gene product to a transcriptional activator by a posttranslational modification event.
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PMID:The intracellular signal for induction of resistance to alkylating agents in E. coli. 300 22

Specific cysteine residues at possible methyl acceptor sites of the Ada protein of Escherichia coli were converted to other amino acids by site-directed mutagenesis of the cloned ada gene of E. coli. Ada protein with the cysteine residue at 321 replaced by alanine was capable of accepting the methyl group from the methylphosphotriester but not from O6-methylguanine or O4-methylthymine of alkylated DNA, whereas the protein with alanine at position 69 accepted the methyl group from the methylated bases but not from the methylphosphotriester. These two mutants were used to elucidate the biological significance of repair of the two types of alkylation lesions. Introduction of the ada gene with the Ala69 mutation into an ada- cell rendered the cell more resistant to alkylating agents with respect to both killing and induction of mutations, but the gene with the Ala321 mutation exhibited no such activity. Replacement of the cysteine residue at position 69, but not at position 321, abolished the ability of Ada protein to promote transcription of both ada and alkA genes in vitro. These results are compatible with the idea that methylation of the cysteine residue at position 69 renders Ada protein active as a transcriptional regulator, whilst the cysteine residue at position 321 is responsible for repair of pre-mutagenic and lethal lesions in DNA. The actions of mutant Ada proteins on the ada and alkA promoters in vivo were investigated using an artificially composed gene expression system. When the ada gene with the Ala69 mutation was introduced into the cell, there was little induction of expression of either the ada or the alkA genes, even after treatment with an alkylating agent, in agreement with the data obtained from studies in vitro. With the Ala321 mutation, however, a considerable degree of ada gene expression occurred without adaptive treatment. The latter finding suggests that the cysteine residue at position 321, which is located near the C terminus of the Ada protein, is involved in regulating activity, as the transcriptional activator.
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PMID:Functional sites of the Ada regulatory protein of Escherichia coli. Analysis by amino acid substitutions. 304

The ada gene of Escherichia coli encodes a 39-kDa protein which serves both as a transcriptional activator of the adaptive response to alkylating agents and as a DNA repair enzyme demethylating O6-methyl-guanine and phosphotriester residues. Here, the isolated Ada protein was found to be readily cleaved into two fragments of similar size by treatment with trypsin, chymotrypsin, subtilisin, or V8 protease. The fragments retained their respective methyltransferase activities. The Ada protein is, therefore, comprised of two stable active domains united by a central hinge region of about 10 amino acids. Post-translational modification of the Ada protein by methylation of a specific cysteine residue in the NH2-terminal domain is known to convert it to an efficient transcriptional activator. This residue has now been identified as Cys-69.
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PMID:Functional domains and methyl acceptor sites of the Escherichia coli ada protein. 316 36

The amino acid sequence of the Bradyrhizobium japonicum nitrogen fixation regulatory protein NifA, as derived from the nucleotide sequence of the nifA gene, was aligned to the corresponding protein sequences from Klebsiella pneumoniae, Rhizobium meliloti and Rhizobium leguminosarum biovar viciae. High conservation was found in the central domain and in the COOH-terminal, putative DNA binding domain, whereas very little homology was present within the first 250 amino acids from the NH2-terminus. Upon deletion of the first 218 amino acids (37% of the protein) and expression of the remainder as a Cat'-'NifA hybrid protein, a fully active, nif-specific transcriptional activator protein was obtained which also retained oxygen sensitivity, a characteristic property of the wild-type B. japonicum NifA protein. In contrast, an unaltered COOH-terminal domain was required for an active NifA protein. Between the central and the DNA binding domains, a so-called interdomain linker region was identified which was conserved in all rhizobial species but missing in the K.pneumoniae NifA protein. Two conserved cysteine residues in this region were changed to serine residues, by oligonucleotide-directed mutagenesis. This resulted in absolutely inactive NifA mutant proteins. Similar null phenotypes were obtained by altering two closely adjacent cysteine residues in the central domain to serine residues. Nif gene activation in vivo by the B.japonicum NifA protein, but not by the K.pneumoniae NifA protein, was sensitive to treatment with chelating agents, and this inhibition could be overcome by the addition of divalent metal ions. On the basis of these observations and previous data on oxygen sensitivity we raise the hypothesis that at least some, if not all, of the four essential cysteine residues may be involved in oxygen reactivity or metal binding or both.
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PMID:Essential and non-essential domains in the Bradyrhizobium japonicum NifA protein: identification of indispensable cysteine residues potentially involved in redox reactivity and/or metal binding. 335 73

Methyl chloride (MeCl) is an abundant environmental mutagen and carcinogen and may be one of several environmental alkylating agents against which the protection of an adaptive response is required in microorganisms. Both MeCl and methyl iodide (MeI), at micromolar concentrations, induced the adaptive response to alkylation damage in Escherichia coli. This response is regulated by the Ada protein which is converted into a transcriptional activator by self-methylation on repair of methylphosphotriesters in methylated DNA. However, using high amounts of Ada protein, activation of Ada occurred in vitro following direct protein methylation by both MeI (in agreement with previously published data) and MeCl. Activation was enhanced when methyl halide treatments were performed in the presence of DNA. An unadapted E. coli cell contains only 2 to 4 molecules of Ada protein, and presents an extremely small target of 2 to 4 specific cysteine residues per cell for activation of Ada by direct protein methylation in vivo. Thus, it is proposed that induction of the adaptive response in vivo initially occurs via efficient repair by the Ada protein of a low number of methylphosphotriesters in DNA. When the cellular Ada protein level has substantially increased, a greater probability of direct methylation and activation of Ada at cysteine-69 by MeCl may sustain and further increase induction of the adaptive response.
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PMID:Induction of the adaptive response of Escherichia coli to alkylation damage by the environmental mutagen, methyl chloride. 767 75

The Escherichia coli aidB gene is part of the adaptive response to DNA methylation damage. Genes belonging to the adaptive response are positively regulated by the ada gene; the Ada protein acts as a transcriptional activator when methylated in one of its cysteine residues at position 69. Through DNaseI protection assays, we show that methylated Ada (meAda) is able to bind a DNA sequence between 40 and 60 base pairs upstream of the aidB transcriptional startpoint. Binding of meAda is necessary to activate transcription of the adaptive response genes; accordingly, in vitro transcription of aidB is dependent on the presence of meAda. Unmethylated Ada protein shows no protection against DNaseI digestion in the aidB promoter region nor does it promote aidB in vitro transcription. The aidB Ada-binding site shows only weak homology to the proposed consensus sequences for Ada-binding sites in E. coli (AAANNAA and AAAGCGCA) but shares a higher degree of similarity with the Ada-binding regions from other bacterial species, such as Salmonella typhimurium and Bacillus subtilis. Based on the comparison of five different Ada-dependent promoter regions, we suggest that a possible recognition sequence for meAda might be AATnnnnnnG-CAA. Higher concentrations of Ada are required for the binding of aidB than for the ada promoter, suggesting lower affinity of the protein for the aidB Ada-binding site. Common features in the Ada-binding regions of ada and aidB are a high A/T content, the presence of an inverted repeat structure, and their position relative to the transcriptional start site. We propose that these elements, in addition to the proposed recognition sequence, are important for binding of the Ada protein.
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PMID:Transcriptional activation of the Escherichia coli adaptive response gene aidB is mediated by binding of methylated Ada protein. Evidence for a new consensus sequence for Ada-binding sites. 771 36

CysB is a transcriptional activator for the cysteine regulon and negatively autoregulates its own gene, cysB. Transcription activation also requires an inducer, N-acetyl-L-serine. CysB is known to bind to activation sites just upstream of the -35 regions of the positively regulated cysJIH, cysK, and cysP promoters and to a repressor site centered at about +1 in the cysB promoter. Additional accessory sites have been found in positively regulated promoters. The hydroxyl radical footprinting experiments reported here indicate that the activation sites CBS-J1, CBS-K1, and CBS-P1 in the cysJIH, cysK, and cysP promoters are composed of two convergently oriented 19-bp half-sites separated by 1 or 2 bp. N-Acetyl-L-serine stimulates binding to these sites as well as to the accessory sites CBS-J2 and CBS-P2, both of which share a similar topology with activation sites. A second topology is found in the accessory site CBS-K2 and the repressor site CBS-B, which contain divergently oriented 19-bp half-sites separated by one or two helical turns. N-Acetyl-L-serine inhibits binding to these two sites. A third topology is present in the cysK and cysP promoters, where an additional half-site is oriented toward the activation site and separated from it by one helical turn. Here, CysB binds to all three half-sites, bending the DNA, and N-acetyl-L-serine decreases the extent of bending. The marked dissimilarities of these half-site arrangements and of their responses to N-acetyl-L-serine suggest that CysB, a homotetramer, binds to them with different combinations of subunits.
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PMID:Hydroxyl radical footprints and half-site arrangements of binding sites for the CysB transcriptional activator of Salmonella typhimurium. 773 Feb 63


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