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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

External factors regulate the formation of pigment protein complexes in facultatively photosynthetic bacteria. The puf operon of Rhodobacter capsulatus encodes the pigment binding proteins of the reaction centre and light-harvesting I complex. Here we demonstrate that a single base-pair exchange within a sequence of dyad symmetry upstream of the puf promoter affects both the oxygen regulation and the light regulation of the formation of reaction-centre and light-harvesting I complexes in Rhodobacter capsulatus. Our results imply that effects of oxygen or light ultimately act on the same regulatory DNA sequence, although it is still unknown how these environmental signals are sensed and transmitted to a transcriptional regulator.
Mol Microbiol 1991 May
PMID:Light and oxygen effects share a common regulatory DNA sequence in Rhodobacter capsulatus. 195

The LAC9 protein of Kluyveromyces lactis is a transcriptional regulator of genes in the lactose-galactose regulon. To regulate transcription, LAC9 must bind to 17-bp upstream activator sequences (UASs) located in front of each target gene. LAC9 is homologous to the GAL4 protein of Saccharomyces cerevisiae, and the two proteins must bind DNA in a very similar manner. In this paper we show that high-affinity, sequence-specific binding by LAC9 dimers is mediated primarily by 3 bp at each end of the UAS: [Formula: see text]. In addition, at least one half of the UAS must have a GC or CG base pair at position 1 for high-affinity binding; LAC9 binds preferentially to the half containing the GC base pair. Bases at positions 2, 3, and 4 in each half of the UAS make little if any contribution to binding. The center base pair is not essential for high-affinity LAC9 binding when DNA-binding activity measured in vitro. However, the center base pair must play an essential role in vivo, since all natural UASs have 17, not 16, bp. Hydroxyl radical footprinting shows that a LAC9 dimer binds an unusually broad region on one face of the DNA helix. Because of the data, we suggest that LAC9 contacts positions 6, 7, and 8, both plus and minus, of the UAS, which are separated by more than one turn of the DNA helix, and twists part way around the DNA, thus protecting the broad region of the minor groove between the major-groove contacts.
Mol Cell Biol 1991 Apr
PMID:Identification of base and backbone contacts used for DNA sequence recognition and high-affinity binding by LAC9, a transcription activator containing a C6 zinc finger. 200 80

Expression of the Saccharomyces cerevisiae gene encoding cytochrome b2 (EC 1.2.2.3), CYB2, was investigated by direct analysis of mRNA transcripts and by measurement of the expression of lacZ fused to the CYB2 control regions. These studies indicated that regulation of the CYB2 gene is subject to several metabolic controls at the transcriptional level: inhibition due to glucose fermentation, induction by lactate, and inhibition in anaerobiosis or in absence of heme biosynthesis. Furthermore, we have shown that the CYB2 promoter contains one cis negative regulatory region and two heme-dependent positive regions, one of which is controlled by the transcriptional regulator CYP1 (HAP1) which is involved in the modulation of the expression of several oxygen-regulated genes. The CYP1 (HAP1)-binding sequence was located by gel retardation and DNase I footprinting experiments and compared with the binding sequences previously characterized in detail (UAS1CYC1, UAS'CYP3 (CYC7), and UASCTT1).
Mol Cell Biol 1991 Jul
PMID:Complex transcriptional regulation of the Saccharomyces cerevisiae CYB2 gene encoding cytochrome b2: CYP1(HAP1) activator binds to the CYB2 upstream activation site UAS1-B2. 204 77

The Fos-Jun complex has been shown to activate transcription through the regulatory element known as the AP-1 binding site. We show that Fos down regulates several immediate-early genes (c-fos, Egr-1, and Egr-2) after mitogenic stimulation. Specifically, we demonstrate that the target for this repression is a sequence of the form CC(A/T)6GG, also known as a CArG box. Whereas Fos bound to the AP-1 site through a domain rich in basic amino acids and associated with Jun via a leucine zipper interaction, mutant Fos proteins lacking these structures were still capable of causing repression. Furthermore, Jun neither enhanced nor inhibited down regulation by Fos. Critical residues required for repression are located within the C-terminal 27 amino acids of c-Fos, since v-Fos and C-terminal truncations of c-Fos did not down regulate. In addition, transfer of 180 c-Fos C-terminal amino acids to Jun conferred upon it the ability to repress. Finally, Fra-1, a Fos-related protein which has striking similarity to Fos in its C-terminal 40 amino acids, also down regulated Egr-1 expression. Thus, Fos is a transcriptional regulator that can activate or repress gene expression by way of two separate functional domains that act on distinct regulatory elements.
Mol Cell Biol 1990 Aug
PMID:Transcriptional activation and repression by Fos are independent functions: the C terminus represses immediate-early gene expression via CArG elements. 211 22

The act gene of Escherichia coli encodes the pyruvate formate-lyase-activating enzyme which is necessary for the post-translational modification of pyruvate formate-lyase. The gene is located 191 bp downstream from the pfl structural gene. Northern blot analysis revealed that the act transcript is monocistronic and that transcription is independent of pfl gene expression. Through mapping of the 5' and 3' ends of the act transcript, sequences could be identified showing similarity to both an Escherichia coli sigma 70 promoter and to a rho-independent transcription terminator. Expression of the act gene was analysed with the aid of chromosomally integrated transcriptional and translational lacZ fusions. The results verified that the act gene is transcribed from its own promoter and that expression of the gene is essentially constitutive. Anaerobiosis led only to a two-fold increase in expression over that observed in aerobically grown cells and this elevated expression was independent of the transcriptional regulator, Fnr. Moreover, effectors such as pyruvate and nitrate, which substantially influence anaerobic transcription of the pfl gene, did not affect act gene expression.
Mol Microbiol 1990 Mar
PMID:Transcriptional analysis of the gene encoding pyruvate formate-lyase-activating enzyme of Escherichia coli. 219 29

The DNA-binding AbrB protein of Bacillus subtilis is an ambiactive transcriptional regulator of genes expressed during the transition state between vegetative growth and the onset of stationary phase and sporulation. Studies on the transcriptional control of AbrB synthesis using abrB-lacZ fusions indicated that the abrB gene was autoregulated. This was consistent with the observation that purified AbrB protein bound specifically to the promoter region of its own gene in DNase I protection experiments. The structural gene mutation abrB4 abolished the autoregulation and purified AbrB4 protein did not have the promoter binding properties associated with the wild-type protein. Both AbrB and AbrB4 proteins were shown to be hexamers of 10,500 Dalton subunits and subunit exchange occurred between the proteins in vitro. However, the presence of only one or two mutant subunits dramaticaly altered the DNA-binding ability of the multimeric protein. The results support a model in which autoregulation of the abrB gene is an important factor in preventing sporulation-associated genes from being expressed during vegetative growth.
Mol Microbiol 1989 Sep
PMID:The transition state transcription regulator AbrB of Bacillus subtilis is autoregulated during vegetative growth. 250 67

FNR, the transcriptional regulator of gene expression of anaerobic respiration in Escherichia coli, contains a cluster of cysteine residues at the amino terminus which resembles the metal-binding domains of metal-binding proteins. It is possible, therefore, (i) that FNR binds metals with the cysteines as ligands and (ii) that this property is related to the regulatory function of FNR. These questions were investigated, with the following results. Approximately 2.4 of the 4 cysteine residues of FNR can be alkylated with iodoacetate in permeabilized aerobic or anaerobic bacteria without the addition of reducing agents. The time required for half-maximal labelling of the cysteines was 50 min in anaerobic bacteria and 6 min in aerobic bacteria. The difference in the reactivity was specific for the cysteines of FNR. These cysteine residues were also highly reactive in anaerobically grown bacteria, when the growth medium contained chelating agents such as 1,10-phenanthroline (15 microM). The effect of the chelating agents was reversed by an excess of divalent metal ions such as Fe(II) or Cu(II) in the medium. The presence of 1,10-phenanthroline (10 microM) also inhibits the expression of fumarate reductase, an FNR-dependent enzyme. These results suggest that FNR exists in two different forms which differ in terms of the reactivity of their cysteine residues to iodoacetate. The interconversion of both forms appears to be regulated by the availability of O2 and by the binding of metal ions. The two forms of FNR may be involved in the regulation of O2-dependent gene expression.
Mol Microbiol 1989 May
PMID:Role of cysteine residues and of metal ions in the regulatory functioning of FNR, the transcriptional regulator of anaerobic respiration in Escherichia coli. 266 93

Responses of the yeast genes encoding 3-hydroxy-3-methylglutaryl coenzyme A reductase, HMG1 and HMG2, to in vivo changes in heme concentrations were investigated. Expression of the genes was determined by direct measurement of the mRNA transcribed from each gene, by direct assay of the enzyme activity encoded by each gene, and by measurement of the expression of lacZ fusions to the control regions of each gene. These studies indicated that expression of HMG1 was stimulated by heme, whereas expression of HMG2 was repressed by heme. The effect of heme on HMG1 expression was mediated by the HAP1 transcriptional regulator and was independent of HAP2. Thus, the genes encoding the 3-hydroxy-3-methylglutaryl coenzyme A reductase isozymes join a growing list of gene pairs that are regulated by heme in opposite ways.
Mol Cell Biol 1989 Dec
PMID:Positive and negative transcriptional control by heme of genes encoding 3-hydroxy-3-methylglutaryl coenzyme A reductase in Saccharomyces cerevisiae. 268 74

Hydrogenase activity and other hydrogenase-related functions can be restored to hydC mutants by the specific addition of nickel salts to the growth medium. These mutants are defective in all three hydrogenase isoenzymes and the restoration is dependent upon protein synthesis. The cellular nickel content of the mutant when grown in LB medium is less than 1% of that of the parental strain. Partial suppression of the hydrogenase phenotype of hydC mutants occurs when growth takes place in a different medium. This correlates with an increased cellular nickel content. The phenotype of the mutant is also fully suppressed by growth in media of very low magnesium content. Such media facilitate nickel uptake via the magnesium transport system, which leads to the acquisition of a normal cellular nickel content. Mutations in the fnr gene, which encodes a transcriptional regulator for several anaerobically expressed enzymes, abolishes hydC expression and gives rise to a defective hydrogenase phenotype. The hydrogenase phenotype of fnr is closely similar to that of hydC in all respects examined. The hydrogenase activity of fnr strains can be restored by the presence of a functional hydC gene on a multicopy plasmid. The hydrogenase phenotype of fnr strains therefore arises indirectly via suppression of hydC, which leads to a low cellular nickel content. Nickel has no influence on fumarate reductase or nitrate reductase activities in fnr strains. The hydrogen-metabolism phenotype of fnr strains is, therefore, dependent upon their ability to acquire nickel from growth media. It is likely that hydC encodes a specific transport system for nickel.
Mol Microbiol 1989 Dec
PMID:Nickel deficiency gives rise to the defective hydrogenase phenotype of hydC and fnr mutants in Escherichia coli. 269 44

We constructed a family of lambda phage and plasmid vectors which facilitate cloning and quantitative analysis of transcriptional regulator in both single and multiple copies. Their expression system was modified from the ara-trp-lac fusion operon of plasmid pMC81 [Casadaban and Cohen, J. Mol. Biol. 138 (1980) 179-207], which is designed to assay both promoters and terminators with a single vehicle. To eliminate transcriptional and translational polar effects liable to occur in the original fusion operon upon insertion of a foreign nucleotide sequence, intracistronic Rho-dependent terminators, that are present within the trpB gene and distal to the cloning site were deleted, and DNA spacers containing stop codons were introduced immediately before and after the cloning site. In analysis of the cloned trp regulatory region, the lambda phage system faithfully reproduced the tight regulation by tryptophan characteristic to the natural trp operon on the E. coli chromosome, whereas the plasmid counterpart exhibited a substantially relaxed response. Comparative studies on the relative strengths of various promoters and terminators have further demonstrated that the lambda phage vector system permits accurate assays of exceptionally strong promoters like Ptrp and lambda pL without disturbing the bacterial growth, while being sensitive enough for detecting low-level transcription under the control of weak promoters or potent terminators. Cloning with the lambda phage vector can be greatly facilitated by transferring the target regulatory site precloned with the plasmid onto the phage genome through in vivo recombination.
 ...
PMID:Construction and characterization of plasmid and lambda phage vector systems for study of transcriptional control in Escherichia coli. 282 83


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