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Query: UNIPROT:P06889 (Mol)
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Rhizobium meliloti FixL and FixJ are members of a symbiotically essential two-component system that regulates nitrogen-fixation genes in response to environmental oxygen concentrations. FixL is a membrane protein that is thought to relay information about oxygen availability to FixJ via a phosphotransfer mechanism. FixJ increases expression of the nifA and fixK genes by activating transcription of the nifA and fixK promoters (p-nifA and p-fixK, respectively). In this study, we examined the relationship between the in vivo activity of FixJ as a transcriptional regulator and its ability to be phosphorylated in vitro by the sensor FixL. FixJ mutants were isolated that showed decreased activity on p-nifA in Escherichia coli. Most of the FixJ mutant proteins also showed decreased activity on the fixK promoter. These mutants were analysed in R. meliloti for activity on p-nifA during vegetative growth, where similarities and differences were observed when compared with their phenotypes in E. coli. Three mutants showing significantly less activity in R. meliloti were examined for symbiotic activity in planta and were found to be ineffective. When these three mutant FixJ proteins were examined in vitro for their ability to be phosphorylated by FixL, two mutants were found to have a significantly decreased ability to accept phosphate from FixL. These findings are discussed in relation to signal transduction in the FixLJ system.
Mol Microbiol 1992 Aug
PMID:Isolation of phosphorylation-deficient mutants of the Rhizobium meliloti two-component regulatory protein, FixJ. 140 47

We have cloned and sequenced the SIN4 gene and determined that SIN4 is identical to TSF3, identified as a negative regulator of GAL1 gene transcription (S. Chen, R.W. West, Jr., S.L. Johnson, H. Gans, and J. Ma, submitted for publication). Yeast strains bearing a sin4 delta null mutation have been constructed and are temperature sensitive for growth and display defects in both negative and positive regulation of transcription. Transcription of the CTS1 gene is reduced in sin4 delta mutants, suggesting that Sin4 functions as a positive transcriptional regulator. Additionally, a Sin4-LexA fusion protein activates transcription from test promoters containing LexA binding sites. The sin4 delta mutant also shows phenotypes common to histone and spt mutants, including suppression of delta insertion mutations in the HIS4 and LYS2 promoters, expression of promoters lacking upstream activation sequence elements, and decreased superhelical density of circular DNA molecules. These results suggest that the sin4 delta mutation may alter the structure of chromatin, and these changes in chromatin structure may affect transcriptional regulation.
Mol Cell Biol 1992 Oct
PMID:Involvement of the SIN4 global transcriptional regulator in the chromatin structure of Saccharomyces cerevisiae. 140 39

AlgR is a transcriptional regulator of mucoidy in Pseudomonas aeruginosa, a critical virulence factor expressed in cystic fibrosis. AlgR belongs to the superfamily of bacterial signal transduction systems, and has been shown to bind to the algD promoter, a critical point in the regulation of mucoidy. This protein, like other typical response regulators, contains highly conserved residues known to be critical for the phosphorylation and signal transduction processes. However, a typical second component interacting with AlgR has not been identified. Here we demonstrate that AlgR undergoes phosphorylation in vitro when interacting with the well-characterized histidine protein kinase CheA. These results indicate that AlgR is capable of undergoing phosphorylation typical of other two-component signal transduction systems. Moreover, the phosphotransfer reaction between CheA and AlgR was found to be affected by the presence of carbamoyl phosphate, acetyl phosphate, and salts of phosphoramidic acid, recently shown to act as small-molecular-weight phospho-donors in the process of phosphorylation of several response regulators. These findings suggest that AlgR may react with intermediary metabolites such as carbamoyl phosphate and acetyl phosphate, and that these processes may play a role in the control of mucoidy in P. aeruginosa.
Mol Microbiol 1992 Oct
PMID:In vitro phosphorylation of AlgR, a regulator of mucoidy in Pseudomonas aeruginosa, by a histidine protein kinase and effects of small phospho-donor molecules. 143 55

We have cloned GAM2, which is required for transcription of STA1, a gene encoding an extracellular glucoamylase in Saccharomyces cerevisiae var. diastaticus. DNA sequence analysis revealed that GAM2 is the same gene as SIN3, known to be a general negative regulator of yeast genes. RNA blot analysis indicated that GAM2/SIN3 also acts as a positive regulator of GAM3/ADR6, which in turn is required for transcription of STA1 and ADH2. These results suggest that GAM2 regulates STA1 expression through transcriptional activation of GAM3 and indicate that GAM2/SIN3 protein is a transcriptional regulator that can play a role in both activation and repression of transcription.
Mol Gen Genet 1992 May
PMID:The Saccharomyces cerevisiae GAM2/SIN3 protein plays a role in both activation and repression of transcription. 160 74

Alpha interferon stimulates transcription by converting the positive transcriptional regulator ISGF3 from a latent to an active form. This receptor-mediated event occurs in the cytoplasm, with subsequent translocation of the activated factor to the nucleus. ISGF3 has two components, termed ISGF3 alpha and ISGF3 gamma. ISGF3 gamma serves as the DNA recognition subunit, while ISGF3 alpha, which appears to consist of three polypeptides, is a target for alpha interferon signaling and serves as a regulatory component whose activation is required to form ISGF3. ISGF3 gamma DNA-binding activity was identified as a 48-kDa polypeptide, and partial amino acid sequence has allowed isolation of cDNA clones. ISGF3 gamma translated in vitro from recombinant clones bound DNA with a specificity indistinguishable from that of ISGF3 gamma purified from HeLa cells. Sequencing of ISGF3 gamma cDNA clones revealed significant similarity to the interferon regulatory factor (IRF) family of DNA binding proteins in the amino-terminal 117 residues of ISGF3 gamma. The other IRF family proteins bind DNA with a specificity related to but distinct from that of ISGF3 gamma. We note sequence similarities between the related regions of IRF family proteins and the imperfect tryptophan repeats which constitute the DNA-binding domain of the c-myb oncoprotein. These sequence similarities suggest that ISGF3 gamma and IRF proteins and the c-myb oncoprotein use a common structural motif for DNA recognition. Recombinant ISGF3 gamma, like the natural protein, interacted with HeLa cell ISGF3 alpha to form the mature ISGF3 DNA-binding complex. We suggest that other IRF family members may participate in signaling pathways by interacting with as yet unidentified regulatory subunits analogous to ISGF3 alpha.
Mol Cell Biol 1992 Aug
PMID:Subunit of an alpha-interferon-responsive transcription factor is related to interferon regulatory factor and Myb families of DNA-binding proteins. 163 Apr 47

We have determined the nucleotide sequences of the genes encoding the fimbrial subunits representative of the known Bacteroides nodosus serogroups. All of the genes are preceded by a highly conserved region which includes the likely promoter and transcriptional regulator sites as well as the ribosome-biding site, and are followed within a short but variable distance by a sequence with the characteristics of a transcription termination or attenuation signal. Based on sequence and organization, the subunits can be divided into two major classes called I (serogroups A, B, C, E, F, G, and I) and II (serogroups D and H). All contain the same seven-amino-acid positively charged leader sequence and conserved hydrophobic amino-terminal sequence typical of type 4 fibriae. Beyond this point the class II subunits are quite different from class I and share features more in common with those from other type 4 fimbriate bacteria, such as Moraxella bovis and Pseudomonas aeruginosa. The larger class I may be further subdivided into two subsets: (i) [A, E, F)(B, I)) and (ii) (C, G). These proteins exhibit three major clusters of variation, at either end of the presumptive disulphide loop which spans the central third of the protein, and near the carboxy-terimus, with dispersed changes in between. The length of the mature subunits varies from 152-156 amino acids, and the variation includes small insertions or deletions in the variable clusters between more conserved domains. The class II subunits are 149 amino acids in length and contain two pairs of cysteine residues: one is at the end of the amino-terminal conserved region, and the other is at the end of the protein. The major variation occurs in the central region of the molecule, and again small insertions or deletions are required to align adjacent conserved domains. There is also a striking absence of silent codon changes in the 5' coding region of all of these genes, indicating that these sequences have a secondary genetic function, probably in recombinational exchange.
Mol Microbiol 1991 Mar
PMID:Gene sequences and comparison of the fimbrial subunits representative of Bacteroides nodosus serotypes A to I: class I and class II strains. 167 19

A variety of stimuli have been identified which initiate transcription-dependent programmed cell death (apoptosis) in specific target cells. Since the withdrawal of androgens induces regression and apoptosis in rat ventral prostate (RVP) epithelial cells, and it is known that the androgen receptor is a transcriptional regulator, we used subtraction cDNA cloning to isolate differentially expressed transcripts from the RVP of androgen ablated rats. In addition to sulfated glycoprotein-2 and glutathione S-transferase (GST), which had been previously described, several other transcripts were found to be elevated 3- to 8-fold in the regressing RVP. DNA sequencing revealed that two of these cDNA clones encode matrix carboxyglutamic acid and gamma-actin, respectively. A third cDNA contained novel sequence information and was named RVP.1. The RVP.1 transcript is expressed at very low levels in the RVP and epididymis of normal adult rats (less than 0.01% of the total mRNA) and is undetectable in other tissues, such as kidney, liver, and muscle. RVP.1 encodes a putative 280-amino acid protein, which shares no significant homology with previously described protein functional domains. We examined the expression of these transcripts in serum-starved NIH 3T3 cells to determine whether any of them are elevated in cells that are growth arrested. It was found that only GST mRNA levels are increased under these conditions. These data may suggest that induction of some genes, such as RVP.1, could be associated with apoptosis, whereas other transcripts, such as GST, may be up-regulated in response to altered rates of cellular metabolism.
Mol Endocrinol 1991 Oct
PMID:Isolation and characterization of transcripts induced by androgen withdrawal and apoptotic cell death in the rat ventral prostate. 172 40

As an additional system for analysing mutations that appear to be specifically induced or directed, we have used a plasmid that contains the mnt repressor gene inserted as an operon fusion with the tet gene of the plasmid pBR322. Thus, the mnt gene product acts as a negative transcriptional regulator of tet gene expression. Mutations inactivating the Mnt repressor are recessive while those destroying operator recognition (Oc) are dominant in conferring tetracycline resistance on the host. When resistance mutations were isolated on plates with high levels of tetracycline they were preferentially mnt- and the plasmids were monomers. Pre-exposure to low concentrations increased the frequency of resistant mutants by 100- to 1000-fold, and the mutations were now mostly Oc, located on one unit of a plasmid multimer. Recessive repressor mutations on one unit would not have been selected. We suggest that the high frequency of mutation in tandem multimeric plasmids may be caused by the formation of single-stranded and hence highly mutable regions by homologous pairing out of register. The role of tetracycline in promoting mutations is discussed.
Mol Microbiol 1991 Oct
PMID:Role of plasmid multimers in mutation to tetracycline resistance. 179 64

AmpR, the transcriptional regulator for the Citrobacter freundii ampC beta-lactamase gene, was purified. The purified AmpR had DNA-binding activity, the same molecular mass (32 kDa) on sodium dodecyl sulphate/polyacrylamide gel electrophoresis as previously described, and N-terminal sequencing of the first 15 amino acids was in agreement with that predicted from the nucleotide sequence. Two mutants were isolated that abolish DNA-binding and beta-lactamase induction and which map in the amino- and carboxyl-terminal ends of AmpR, respectively. The mutation in the amino terminus (S35F) was located in a helix-turn-helix region showing high homology to other members of the LysR regulator family. Therefore this mutation may directly abolish the contact between AmpR and its operator sequence. It is suggested that the C-terminal mutation (Y264N) affects subunit interactions in AmpR. One constitutive mutant was isolated which mapped in the centre of the ampR gene. This G102E mutant leads to constitutive beta-lactamase expression in the absence of both beta-lactam inducer and ampG, a gene essential for induction in wild-type enterobacteria. Another mutant protein, D135Y, showed wild-type properties in an ampG+ and an ampG::kan background, but could, unlike wild-type AmpR, activate the ampC gene in an ampG1 mutant background. It is thought that ampG1 is a missense mutant. These two types of ampR mutants suggest that activation of ampC transcription is dependent on the conversion of AmpR into a transcriptional activator and that this activation may normally involve interactions with AmpG.
Mol Microbiol 1991 Jul
PMID:Purification and mutant analysis of Citrobacter freundii AmpR, the regulator for chromosomal AmpC beta-lactamase. 194 5

The nuclear phosphoprotein c-Jun, encoded by the proto-oncogene c-jun, is a major component of the AP-1 complex. A potent transcriptional regulator, c-jun is also able to transform normal rat embryo cells in cooperation with an activated c-Ha-ras gene. By deletion analysis, we identified the regions of c-Jun encoding transformation and transactivation functions. Our studies indicate that there is a direct correlation between the ability of the c-Jun protein to activate transcription and cotransform rat embryo cells. The regions involved in these functions include the conserved leucine zipper/DNA binding domain and an effector domain near its N terminus. This N-terminal region spans amino acids 61 to 146 of the c-Jun protein and is highly conserved among all Jun family members. These results support the hypothesis that c-Jun transforms cells by stimulating the expression of transformation-mediating genes.
Mol Cell Biol 1991 Dec
PMID:The transactivating domain of the c-Jun proto-oncoprotein is required for cotransformation of rat embryo cells. 194 89


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