SEARCH · PubMed Health

Results for “repressor proteins”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 289 records · Page 16Linked to original sources

PubMed2001

Glutamine synthetases of Corynebacterium glutamicum: transcriptional control and regulation of activity.

Regulation of glnA expression and glutamine synthetase I activity was analyzed in Corynebacterium glutamicum. Transcription is regulated by the global repressor protein AmtR, essential for derepression of glnA transcription are GlnK and uridylyltransferase, key proteins of the C. glutamicum nitrogen regulatory system. Glutamine synthetase I activity is controlled by adenylylation/deadenylylation via adenylyltransferase. The gene encoding this bifunctional enzyme, glnE, was isolated and its function was characterized by deletion analysis. Upstream of glnE, a second gene encoding a GSI-type protein in C. glutamicum was isolated. This gene, designated glnA2, forms an operon with glnE, its transcription is not regulated and neither its deletion or overexpression showed any effect. Therefore, the physiological role of glnA2 remains unclear.

Bacterial Proteins↗

PubMed1987

A broad-host-range expression vector based on the pL promoter of coliphage lambda: regulated synthesis of human interleukin 2 in Erwinia and Serratia species.

We report the construction of a broad-host-range expression vector based on an RSF1010-derived replicon. The vector carries the strong leftward promoter (pL) of coliphage lambda as well as the cI857 allele, which codes for a thermolabile repressor protein. The coding region of mature human interleukin 2, which is preceded by the ner ribosome binding site of phage Mu, was cloned downstream from the pL promoter. The plasmid was introduced into Erwinia and Serratia species by means of mobilization. Heat-inducible synthesis of interleukin 2 protein was obtained, showing that the pL promoter is functional in these genera. As in Escherichia coli, the bulk of the overproduced protein was present in an insoluble form.

Bacteriophage lambda↗

PubMed1995

AbrB modulates expression and catabolite repression of a Bacillus subtilis ribose transport operon.

A Bacillus subtilis ribose transport operon (rbs) was shown to be subject to AbrB-mediated control through direct AbrB-DNA binding interactions in the vicinity of the promoter. Overproduction of AbrB was shown to relieve catabolite repression of rbs during growth in the presence of poorer carbon sources such as arabinose but had much less effect when cells were grown in the presence of glucose, a rapidly metabolizable carbon source. A ccpA mutation relieved catabolite repression of rbs under all conditions tested. One of the AbrB-binding sites on the rbs promoter contains the putative site of action for the B. subtilis catabolite repressor protein CcpA, suggesting that competition for binding to this site could be at least partly responsible for modulating rbs expression during carbon-limited growth.

Bacillus subtilis↗

PubMed1996

The Cyc8 (Ssn6)-Tup1 corepressor complex is composed of one Cyc8 and four Tup1 subunits.

The Cyc8 (Ssn6)-Tup1 corepressor complex is required for repression in several important regulatory systems in yeast cells, including glucose repression and mating type. Cyc8-Tup1 is recruited to target genes by interaction with diverse repressor proteins that bind directly to DNA. Since the complex has a large apparent molecular mass of 1,200 kDa on nondenaturing gels (F. E. Williams, U. Varanasi, and R. J. Trumbly, Mol. Cell. Biol. 11:3307-3316, 1991), we used a variety of approaches to determine its actual subunit composition. Immunoprecipitation of epitope-tagged complex and reconstitution of the complex from in vitro-translated proteins demonstrated that only the Cyc8 and Tup1 proteins were present in the complex. Hydrodynamic properties showed that these proteins have unusually large Stokes radii, low sedimentation coefficients, and high frictional ratios, all characteristic of asymmetry which partly accounts for the apparent high molecular weight. Calculation of native molecular weights from these properties indicated that the Cyc8-Tup1 complex is composed of one Cyc8 subunit and four Tup1 subunits. This composition was confirmed by reconstitution of the complex from Cyc8 and Tup1 expressed in vitro and analysis by one- and two-dimensional gel electrophoresis.

Base Sequence↗

PubMed1992

Protein synthesis inhibitors differentially superinduce c-fos and c-jun by three distinct mechanisms: lack of evidence for labile repressors.

Protein synthesis inhibitors strongly augment and prolong the usually transient induction of c-fos and c-jun by growth factors, phorbol esters etc., a phenomenon termed superinduction which is conventionally regarded as a secondary consequence of translational arrest. Our recent demonstration that some inhibitors can act positively as nuclear signalling agonists compromises this view and necessitates a re-evaluation of superinduction. First, we show that labile repressors, widely postulated to act negatively on diverse superinducible genes, are not involved in regulating c-fos and c-jun. Secondly, two components of c-fos and c-jun superinduction, namely the delay in shutting off transcription and stabilization of their mRNAs, arise from translational arrest and are common to all protein synthesis inhibitors. Thirdly, the recently described capacity to act positively as nuclear signalling agonists to stimulate pp33/pp15 phosphorylation is restricted to compounds such as anisomycin and cycloheximide; these, but not emetine or puromycin, will induce c-fos/c-jun on their own. Fourthly, the translational arrest-related components of superinduction are dissociable from the signalling agonist effects at sub-inhibitory concentrations of anisomycin, under which conditions a new type of c-fos/c-jun superinduction with 'spike' kinetics is observed. Finally, we show that in response to EGF plus anisomycin, the nuclear signalling responses are themselves augmented and prolonged in a manner that corresponds to c-fos/c-jun superinduction under these conditions.

Animals↗

PubMed2006

Loopless Rop: structure and dynamics of an engineered homotetrameric variant of the repressor of primer protein.

The repressor of primer (Rop) protein has become a steady source of surprises concerning the relationship between the sequences and the structures of several of its mutants and variants. Here we add another piece to the puzzle of Rop by showing that an engineered deletion mutant of the protein (corresponding to a deletion of residues 30-34 of the wild-type protein and designed to restore the heptad periodicity at the turn region) results in a complete reorganization of the bundle which is converted from a homodimer to a homotetramer. In contrast (and as previously shown), a two-residue insertion, which also restores the heptad periodicity, is essentially identical with wild-type Rop. The new deletion mutant structure is a canonical, left-handed, all-antiparallel bundle with a completely different hydrophobic core and distinct surface properties. The structure agrees and qualitatively explains the results from functional, thermodynamic, and kinetic studies which indicated that this deletion mutant is a biologically inactive hyperstable homotetramer. Additional insight into the stability and dynamics of the mutant structure has been obtained from extensive molecular dynamics simulations in explicit water and with full treatment of electrostatics.

Amino Acid Sequence↗

PubMed1998

Isolation and structure of repressor-like proteins from the archaeon Sulfolobus solfataricus. Co-purification of RNase A with Sso7c.

The thermostable histone-like protein Sso7c (Sso for Sulfolobus solfataricus) from the archaeon Sulfolobus solfataricus was purified from the supernatant of acid-soluble cell lysates. Reverse phase HPLC of an apparently homogeneous Sso7c protein fraction from Mono S chromatography resulted in resolution of three further peaks. Sequence analysis revealed one of these components to be bovine RNase A, originating from the culture medium and explaining the RNA hydrolyzing activities of Sso7 preparations previously described. Sequence analysis of pure Sso7c showed an epsilon-Lys methylation pattern identical to that of Sso7d and a single Gln --> Glu mutational difference at position 13. The remaining two proteins obtained after HPLC separation were identified as homologues of bacterial repressor-like proteins. Thus, the existence of repressor-like proteins was demonstrated at the protein level in archaea, raising the question of structural and functional consequences of these proteins on the otherwise eukaryotic-like basal transcriptional machinery in archaea.

Amino Acid Sequence↗

PubMed2000

Repression of tax-mediated human t-lymphotropic virus type 1 transcription by inducible cAMP early repressor (ICER) protein in peripheral blood mononuclear cells.

Human T-lymphotropic virus type 1 (HTLV-1) infection causes adult T-cell leukemia and is characterized by long periods of clinical latency with low levels of viral production. Transcription of HTLV-1 is controlled through sequences in the promoter and enhancer regions of the long terminal repeat of the integrated provirus. Important among these sequences are three 21 bp imperfect repeats responsive to the viral oncogenic protein Tax (TRE). Members of the CREB/ATF-1/CREM family of transcription factors bind to TRE-1 and are critical for HTLV-1 transcription. Other less studied family members include the inducible cAMP early repressor (ICER) proteins. ICER proteins lack phosphorylation and activation domains and are potent inhibitors of transcription. The ability of ICER to bind TRE-1 and its effects on HTLV-1 Tax mediated transcription have not been studied in the natural cell targets of the virus, peripheral blood mononuclear cells (PBMC). We show that ICER mRNA levels are low in quiescent PBMC, but rise and remain elevated for up to 18 hr after mitogenic stimulation of these cells. Electrophoretic mobility shift assays using recombinant Tax and ICER demonstrate that ICER binds TRE-1 and that binding is increased in the presence of Tax. Furthermore, over expression of ICER IIgamma suppressed Tax-mediated transcription whereas an anti-sense ICER II plasmid designed to block endogenous ICER enhanced Tax-mediated transcription in activated PBMC. Together our data indicate that ICER inhibits Tax-mediated transcription in activated PBMC and suggest a role for ICER in maintenance of HTLV-1 persistence.

Adult↗

PubMed1999

Probing the physical basis for trp repressor-operator recognition.

The bacterial repressor protein, trp repressor, is one of the best studied transcriptional regulatory proteins in terms of function, structure, dynamics and stability. Despite these significant advances, the structural and energetic basis for the specific recognition of its operator sites by trp repressor remains poorly understood. In fact, recognition in this system is controled by the binding of the co-repressor ligand, l-tryptophan, as well as by conformational and dynamic properties of the operator targets, DNA sequence-dependent control of the oligomerization properties of the repressor, water-mediated interactions, and specific interactions involving the peptide backbone and phosphate moieties. Moreover, only one direct contact between the protein and the DNA is evident from the crystallographically determined structure of the complex. In an attempt to better define how the various sequence elements in the operator target contribute to this complex control of affinity and cooperativity of trp repressor binding, we have studied the binding of trp repressor to a series of mutated operator targets using fluorescence anisotropy, which provides very high quality data allowing fairly precise estimations of the affinities involved. We conclude from these studies that even on very small (25 bp) targets, the repressor binds slightly cooperatively, populating a 2:1 dimer/DNA complex, and then at higher concentrations a third dimer is bound with significantly lower affinity, revealing an inherent asymmetry in the trpEDCBA-derived target. Investigation of the basis for the asymmetry implicates the identity of the second base in the so-called structural half-site GNACT, which apparently influences the switch between tandem and simple binding. Mutation of the C or the T bases in the structural half-site abolishes all specificity in binding, and alteration of the single direct contact, the G of the structural half-site, or the central TTAA significantly lowers the affinity of the dimer for its site, without modifying the apparent cooperativity. Finally, we note that the order of affinity is conserved in the absence of the co-repressor, and moreover, it is in all cases significantly higher than that observed for holo-repressor binding to non-specific DNA, indicating that one cannot simply equate apo-repressor and non-specific binding.

Bacterial Proteins↗

PubMed1997

Regulation of expression of the ethanol dehydrogenase gene (adhE) in Escherichia coli by catabolite repressor activator protein Cra.

The adhE gene encodes ethanol dehydrogenase and is located at min 27.9 of the Escherichia coli chromosome. Expression of adhE is about 10-fold higher in cells grown anaerobically than in cells grown aerobically and is dependent on both transcriptional and posttranscriptional factors. In this study, a trans-regulatory element repressing adhE expression was characterized by genetic and biochemical approaches. A mutation downregulating adhE expression was mapped at min 2 of the chromosome. DNA sequence analysis revealed a missense mutation in the cra gene, formerly known as fruR. The cra gene encodes a catabolite repressor-activator protein (Cra) involved in the modulation of carbon flow in E. coli. The mutant protein (Cra*) sustained an Arg148-->His substitution causing 1.5- and 3-fold stronger repression of adhE transcription under anaerobic and aerobic conditions, respectively. By contrast, cra null mutants displayed 1.5- and 4-fold increased adhE transcription under those conditions. Disruption of the cra gene did not abolish the anaerobic activation of the adhE gene but diminished it twofold. Cra and Cra* were purified as fusion proteins tagged with an N-terminal 6xHis element. In vitro, both fusion proteins showed binding to the adhE promoter region and to the control fruB promoter region, which is a known Cra target. However, only 6xHis-tagged Cra, and not 6xHis-Cra*, was displaced from the DNA target by the effector, fructose-1-phosphate (F1P), suggesting that the mutant protein is locked in a promoter-binding conformation and is no longer responsive to F1P. We suggest that Cra helps to tighten the control of adhE transcription under aerobic conditions by its repression.

Aerobiosis↗

PubMed1990

Autoregulation of Escherichia coli purR requires two control sites downstream of the promoter.

The expression of Escherichia coli purR, which encodes the pur regulon repressor protein, is autoregulated. Autoregulation at the level of transcription requires two operator sites, designated purRo1 and purRo2 (O1 and O2). Operator O1 is in the region of DNA between the transcription start site and the site for translation initiation, and O2 is in the protein-coding region. The repressor protein binds noncooperatively to O1 with a sixfold-higher affinity than to O2, and saturation of O1 by the repressor precedes saturation of O2. Both O1 and O2 function in the two- to threefold autoregulation in vivo, as determined by measurement of beta-galactosidase and mRNA from purR-lacZ translational fusions. Of all the genes thus far known to be regulated by the Pur repressor, only purR employs a two-operator mechanism.

Amino Acid Sequence↗

PubMed2001

Insulin regulation of protein translation repressor 4E-BP1, an eIF4E-binding protein, in renal epithelial cells.

BACKGROUND: Augmented protein translation by insulin involves activation of eukaryotic initiation factor 4E (eIF4E) that follows release of eIF4E from a heterodimeric complex by phosphorylation of its inhibitory binding protein, 4E-BP1. We examined insulin regulation of 4E-BP1 phosphorylation in murine proximal tubular epithelial cells. METHODS AND RESULTS: Insulin (1 nmol/L) increased de novo protein synthesis by 58 +/- 11% (P < 0.001). Insulin also augmented 4E-BP1 phosphorylation and phosphatidylinositol 3-kinase (PI 3-kinase) activity in antiphosphotyrosine immunoprecipitates. This could be prevented by PI 3-kinase inhibitors, Wortmannin, and LY294002. Insulin also activated Akt that lies downstream of PI 3-kinase. Rapamycin abrogated 4E-BP1 phosphorylation in response to insulin, suggesting involvement of mammalian target of rapamycin (mTOR), a kinase downstream of Akt. Insulin-stimulated phosphorylation of 4E-BP1 was also inhibited by PD098059, implying involvement of Erk-1/-2 mitogen-activated protein (MAP) kinase. An increase in Erk-1/-2 type MAP kinase activity by insulin was directly confirmed in an immunokinase assay and was found to be PI 3-kinase dependent. CONCLUSIONS: In proximal tubular epithelial cells, insulin augments 4E-BP1 phosphorylation, which is PI 3-kinase and mTOR dependent. The requirement for Erk-1/-2 MAP kinase activation for 4E-BP1 phosphorylation by insulin suggests a cross-talk between PI 3-kinase and Erk-1/-2-type MAP kinase pathways.

Adaptor Proteins, Signal Transducing↗

PubMed1989

Genetic and structural analysis of the ColE1 Rop (Rom) protein.

Repressor of primer (Rop) is a small dimeric protein that participates in the mechanism that controls the copy number of plasmid of the ColE1 family by increasing the affinity between two complementary RNAs. The Rop dimer is a bundle of four tightly packed alpha-helices that are held together by hydrophobic interactions. We have systematically altered, by site directed mutagenesis, most of the solvent exposed amino acids of the Rop bundle and we have identified the alterations that cause a decrease of the activity of the regulatory molecule. We conclude that Rop folding is rather insensitive to amino acid substitutions and to other mutations as drastic as deletions and insertions. Looking along the 2-fold symmetry axis the amino acid side chains whose alterations affect the function of Rop are all located on one side of the molecule. Furthermore they are clustered at the extremities of the alpha-helix bundle, the only exception being the aromatic ring of Phe-14.

Amino Acid Sequence↗

PubMedDate not supplied

Imaging the asymmetrical DNA bend induced by repressor activator protein 1 with scanning tunneling microscopy.

The yeast Repressor Activator Protein 1 (RAP1) binds a 13-bp consensus found in many transcriptional regulatory regions, in silencer elements, and in telomeric repeat DNA of Saccharomyces cerevisiae. Gel retardation assays suggest that RAP1 bends DNA as it binds, with the vertex of the angle located 5' of the consensus. We show that removal of 230 aa in the N-terminus of RAP1 reduces the aberrant electrophoretic mobility of the protein-DNA complex, while removal of a C-terminal domain of RAP1 causes even greater distortion. To demonstrate that the aberrant electrophoretic mobility is really due to a bend in the double helix, the RAP1-DNA complex was analyzed by Scanning Tunnelling Microscopy (STM). The efficiency and accuracy of binding is checked in parallel by standard Transmission Electron Microscopy (TEM). Due to the use of high-angle shadowing of freeze-dried samples at low temperatures, the STM images allow us to confirm that RAP1 binding induces a DNA bend > 50 degrees, while the binding of the minimal DNA-binding domain shows significantly less distortion of the DNA helix.

DNA↗

PubMed1991

P sequences of Drosophila subobscura lack exon 3 and may encode a 66 kd repressor-like protein.

Several P homologous sequences have been cloned and sequenced from Drosophila subobscura. These sequences are located at the 85DE region of the O chromosome and at least three of them are organized in tandem. We have identified four copies which exhibit strong similarity between them. All of the isolated elements are truncated at the 5' and 3' ends. They have lost the inverted terminal repeats and exon 3, but maintain exons 0, 1 and 2. They are transcribed producing a polyadenylated RNA. The structure of these transcripts suggests that they are able to encode a 66 kd repressor-like protein, but not a functional transposase. We ask about the biological role of a potential repressor protein in this species.

Amino Acid Sequence↗

PubMed2003

Ethylene regulates arabidopsis development via the modulation of DELLA protein growth repressor function.

Phytohormones regulate plant development via a poorly understood signal response network. Here, we show that the phytohormone ethylene regulates plant development at least in part via alteration of the properties of DELLA protein nuclear growth repressors, a family of proteins first identified as gibberellin (GA) signaling components. This conclusion is based on the following experimental observations. First, ethylene inhibited Arabidopsis root growth in a DELLA-dependent manner. Second, ethylene delayed the GA-induced disappearance of the DELLA protein repressor of ga1-3 from root cell nuclei via a constitutive triple response-dependent signaling pathway. Third, the ethylene-promoted "apical hook" structure of etiolated seedling hypocotyls was dependent on the relief of DELLA-mediated growth restraint. Ethylene, auxin, and GA responses now can be attributed to effects on DELLA function, suggesting that DELLA plays a key integrative role in the phytohormone signal response network.

Arabidopsis↗

PubMed2004

Cloning and sequencing analysis of the repressor gene of temperate mycobacteriophage L1.

The wild-type and temperature-sensitive (ts) repressor genes were cloned from the temperate mycobacteriophage L1 and its mutant L1cIts391, respectively. A sequencing analysis revealed that the 131st proline residue of the wild-type repressor was changed to leucine in the ts mutant repressor. The 100% identity that was discovered between the two DNA regions of phages L1 and L5, carrying the same sets of genes including their repressor genes, strengthened the speculation that L1 is a minor variant of phage L5 or vice versa. A comparative analysis of the repressor proteins of different mycobacteriophages suggests that the mycobacteriophage-specific repressor proteins constitute a new family of repressors, which were possibly evolved from a common ancestor. Alignment of the mycobacteriophage-specific repressor proteins showed at least 7 blocks (designated I-VII) that carried 3-8 identical amino acid residues. The amino acid residues of blocks V, VI, and some residues downstream to block VI are crucial for the function of the L1 (or L5) repressor. Blocks I and II possibly form the turn and helix 2 regions of the HTH motif of the repressor. Block IV in the L1 repressor is part of the most charged region encompassing amino acid residues 72-92, which flanks the putative N-terminal basic (residues 1-71) and C-terminal acidic (residues 93-183) domains of L1 repressor.

Amino Acid Sequence↗

PubMed1984

Analysis in vivo of factors affecting the control of transcription initiation at promoters containing target sites for trp repressor.

An investigation of repression in the trp system of Escherichia coli was undertaken using operon fusions and plasmids constructed via recombinant DNA technology. The promoters of the trp operon and the trpR gene were fused to lacZ, enabling the activity of these promoters to be evaluated under various conditions through measurements of beta-galactosidase production. In confirmation of earlier studies, the trpR gene was shown to be regulated autogenously. This control feature of the trp system was found to maintain intracellular Trp repressor protein at essentially invariant levels under most conditions studied. Increasing the trpR+ gene dosage did not significantly elevate Trp repressor protein levels, nor did the introduction of additional operator "sinks" result in significantly decreased levels of Trp repressor protein. Definite alterations in intracellular Trp repressor protein levels were achieved only by subverting the normal trpR regulatory elements. The placement of the lacUV5 or the lambda PL promoters upstream of the trpR gene resulted in significant increases in repression of the trp system. Substituting the primary trp promoter/operator for the native trpR promoter/operator resulted in an altered regulatory response of the trp system to tryptophan limitation or excess. The regulation of the trpR gene effectively imparts a broad range of expression to the trp operon in a manner finely attuned to fluctuations in intracellular tryptophan levels.

Bacterial Proteins↗