Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Binding of the Lac repressor to its operator DNA controls the expression of the genes of the lac operon of Escherichia coli. Lac repressor's affinity for the lac operator is diminished by an inducer that affects the structure of the repressor tetramer. Here we report the cloning and sequencing of the mutant Lac repressor i-t gene, whose product, the LacR-t repressor, shows a higher affinity for the inducer isopropyl-beta-D-thiogalactopyranoside (IPTG) and a lower affinity for the lac operator than the wild-type repressor. We show that the altered phenotype is due to a single amino acid residue replacement; the alanine residue at position 110 in the wild-type is replaced by threonine in i-t. Other amino acid residues in position 110 have been shown to result in an i-s phenotype. For the i-s-substitution of alanine 110 with lysine we demonstrate an increase in the affinity for operator DNA and a decrease in the affinity for IPTG. Thus, A110--> K shows the opposite effect to A110-->T on the repressor protein. We explain the phenotype of the LacR mutants by displacements of the conformational equilibrium for the dimeric repressor unit between RR (high operator affinity, low inducer affinity) and R*R* (low operator affinity, high inducer affinity) towards R*R* in the i-t and towards RR in the i-s mutant in position 110 with respect to the wild-type. The putative structures of the wild-type and mutant Lac repressors confirm this conclusion.
J Mol Biol 1996 Apr 05
PMID:The side-chain of the amino acid residue in position 110 of the Lac repressor influences its allosteric equilibrium. 864 15

The Streptomyces reticuli cellulase (Cell, Avicelase) hydrolyzes crystalline cellulose (Avicel) efficiently to cellobiose. The synthesis of the enzyme is induced by Avicel and repressed by glucose. DNA-binding proteins were purified from induced S. reticuli mycelia by affinity chromatography using the upstream region of the cell gene linked to Sepharose. The enriched protein(s) provoked a gel electrophoresis mobility shift of the upstream region, irrespective of the presence or absence of a 14-bp palindromic sequence, and enhanced the transcription of the cell gene by the S. reticuli RNA polymerase in vitro. The binding site (GTGACTGAGCGCCG) for the protein(s) was located in the vicinity of a DNA bend upstream of the transcriptional start site. Results of physiological studies, deletion and gel-shift analyses lead to the conclusion that a 14-bp palindrome (TGGGAGCGCTCCCA)--situated between the transcriptional start site and the structure gene--is the operator for a repressor protein. The data presented suggest that the two identified cis-acting elements, in cooperation with an activator and a repressor, mediate regulation of cell transcription.
Mol Gen Genet 1996 May 23
PMID:The synthesis of the Streptomyces reticuli cellulase (avicelase) is regulated by both activation and repression mechanisms. 866 29

Our group has previously reported that the nuclear factor Yin-Yang 1 (YY1), a ubiquitous DNA-binding protein, is able to interact with a silencer element (BE) in the gamma interferon (IFN-gamma) promoter region. In this study, we demonstrated that YY1 can directly inhibit the activity of the IFN-gamma promoter by interacting with multiple sites in the promoter. In cotransfection assays, a YY1 expression vector significantly inhibited IFN-gamma promoter activity. Mutation of the YY1 binding site in the native IFN-gamma promoter was associated with an increase in the IFN-gamma promoter activity. Analysis of the DNA sequences of the IFN-gamma promoter revealed a second functional YY1 binding site (BED) that overlaps with an AP1 binding site. In this element, AP1 enhancer activity was suppressed by YY1. Since the nuclear level of YY1 does not change upon cell activation, our data support a model that the nuclear factor YY1 acts to suppress basal IFN-gamma transcription by interacting with the promoter at multiple DNA binding sites. This repression can occur through two mechanisms: (i) cooperation with an as-yet-unidentified AP2-like repressor protein and (ii) competition for DNA binding with the transactivating factor AP1.
Mol Cell Biol 1996 Sep
PMID:The nuclear factor YY1 suppresses the human gamma interferon promoter through two mechanisms: inhibition of AP1 binding and activation of a silencer element. 875 32

The CytR repressor protein relies on protein-protein interactions to the cAMP-CRP complex to bind its operators with sufficiently high affinity to repress transcription. Here, the quaternary structure of CytR and the mechanism underlying the cooperative binding of CytR and cAMP-CRP have been analyzed. Using a modified Ferguson analysis in which protein-DNA complexes are separated in a non-denaturing gel system, we show that CytR binds its operators as a dimer alone as well as in a ternary complex with cAMP-CRP. Analyses of DNA binding of CytR at low protein concentrations indicate that CytR is a dimer in solution at physiological concentrations. Moreover, the CytR inducer cytidine was found not to have any effect on the oligomerization of free CytR or DNA bound CytR. Thus, these data rule out the possibility that the cooperative DNA binding of CytR and cAMP-CRP involves induced dimerization of CytR, and they suggest that cytidine interrupts the cooperative binding of CytR and cAMP-CRP solely by perturbing the protein-protein interactions between the two proteins.
J Mol Biol 1996 Jul 12
PMID:CytR/cAMP-CRP nucleoprotein formation in E. coli: the CytR repressor binds its operator as a stable dimer in a ternary complex with cAMP-CRP. 876 93

Cap-dependent protein synthesis in animal cells is inhibited by heat shock, serum deprivation, metaphase arrest, and infection with certain viruses such as adenovirus (Ad). At a mechanistic level, translation of capped mRNAs is inhibited by dephosphorylation of eukaryotic initiation factor 4E (eIF-4E) (cap-binding protein) and its physical sequestration with the translation repressor protein BP-1 (PHAS-I). Dephosphorylation of BP-I blocks cap-dependent translation by promoting sequestration of eIF-4E. Here we show that heat shock inhibits translation of capped mRNAs by simultaneously inducing dephosphorylation of eIF-4E and BP-1, suggesting that cells might coordinately regulate translation of capped mRNAs by impairing both the activity and the availability of eIF-4E. Like heat shock, late Ad infection is shown to induce dephosphorylation of eIF-4E. However, in contrast to heat shock, Ad also induces phosphorylation of BP-1 and release of eIF-4E. BP-1 and eIF-4E can therefore act on cap-dependent translation in either a mutually antagonistic or cooperative manner. Three sets of experiments further underscore this point: (i) rapamycin is shown to block phosphorylation of BP-1 without inhibiting dephosphorylation of eIF-4E induced by heat shock or Ad infection, (ii) eIF-4E is efficiently dephosphorylated during heat shock or Ad infection regardless of whether it is in a complex with BP-1, and (iii) BP-1 is associated with eIF-4E in vivo regardless of the state of eIF-4E phosphorylation. These and other studies establish that inhibition of cap-dependent translation does not obligatorily involve sequestration of eIF-4E by BP-1. Rather, translation is independently regulated by the phosphorylation states of eIF-4E and the 4E-binding protein, BP-1. In addition, these results demonstrate that BP-1 and eIF-4E can act either in concert or in opposition to independently regulate cap-dependent translation. We suggest that independent regulation of eIF-4E and BP-1 might finely regulate the efficiency of translation initiation or possibly control cap-dependent translation for fundamentally different purposes.
Mol Cell Biol 1996 Oct
PMID:Cap-binding protein (eukaryotic initiation factor 4E) and 4E-inactivating protein BP-1 independently regulate cap-dependent translation. 881 58

Drosophila P elements are mobile DNA elements that encode an 87-kDa transposase enzyme and transpositional repressor proteins. One of these repressor proteins is the 207-amino-acid KP protein which is encoded by a naturally occurring P element with an internal deletion. To study the molecular mechanisms by which KP represses transposition, the protein was expressed, purified, and characterized. We show that the KP protein binds to multiple sites on the ends of P-element DNA, unlike the full-length transposase protein. These sites include the high-affinity transposase binding site, an 11-bp transpositional enhancer, and, at the highest concentrations tested, the terminal 31-hp inverted repeats. The DNA binding domain was localized to the N-terminal 98 amino acids and contains a CCHC sequence, a potential metal binding motif. We also demonstrate that the KP repressor protein can dimerize and contains two protein-protein interaction regions and that this dimerization is essential for high-affinity DNA binding.
Mol Cell Biol 1996 Oct
PMID:The Drosophila P-element KP repressor protein dimerizes and interacts with multiple sites on P-element DNA. 881 74

We previously have shown that a chromosomally integrated copy of the tra gene of plasmid pIJ101 under the control of the KorA repressor protein, which regulates transcription of tra as well as its own synthesis, can promote the conjugal transfer of both chromosomal and plasmid genes in Streptomyces lividans. Using an antibody generated against a fusion protein containing the C-terminal portion of Tra, we show here that this essential conjugation protein is present in membrane fractions of both surface-grown S. lividans, which mate readily, and of cells grown in liquid culture, where mating has not been found. Expression of Tra during the S. lividans life cycle was temporally regulated and was reduced late during vegetative growth so that little or no Tra protein was detected in cells as they began to differentiate morphologically and produce secondary metabolites. Comparison of the membrane concentration of Tra protein with tra mRNA concentration during the S. lividans life cycle indicated that the disappearance of Tra is post-transcriptionally controlled and thus is not mediated by KorA. The results of 'interrupted mating' experiments, together with the time of appearance of Tra in S. lividans membranes, indicate that the intermycelial transfer of pIJ101 in S. lividans is complete by the onset of cellular differentiation.
Mol Microbiol 1996 Mar
PMID:Plasmid transfer and expression of the transfer (tra) gene product of plasmid pIJ101 are temporally regulated during the Streptomyces lividans life cycle. 883 Feb 69

The filamentous fungus Trichoderma reesei forms two specific, xylan-inducible xylanases encoded by xyn1 and xyn2 to degrade the beta-1,4-D-xylan backbone of hemicelluloses. This enzyme system is formed in the presence of xylan, but not glucose. The molecular basis of the absence of xylanase I formation on glucose was the purpose of this study. Northern blotting of the xyn1 transcript as well as the use of the Escherichia coli hygromycin B phosphotransferase-encoding gene (hph) as a reporter consistently showed that the basal expression of xyn1 was affected by glucose, whereas its induction by xylan remained uninfluenced. The repression of basal xyn1 transcription is mediated by the carbon catabolite repressor protein Cre1, which in vivo binds to two of four consensus sites (5'-SYG-GRG-3') in the xyn1 promoter, which occurred in the form of an inverted repeat. T. reesei strains, bearing a xyn1::hph reporter construct, in which four nucleotides from the middle of the inverted repeat had been removed, expressed hph on glucose at a level comparable to that observed during growth on a carbon catabolite derepressing carbon source. Northern analysis of xyn1 expression in a T. reesei mutant strain (RUT C-30), which contains a truncated, non-functional cre1 gene, also confirmed basal transcription of xyn1. In this strain, xyn1 transcription was still inducible by xylose or xylan to an even higher degree than in the wild-type strain, suggesting that induction overcomes glucose repression at the level of xyn1 expression. Based on these data, we postulate that basal transcription of xyn1 is repressed by glucose and mediated by an inverted repeat of the consensus motif for Cre1-mediated carbon catabolite repression.
Mol Microbiol 1996 Sep
PMID:Carbon catabolite repression of xylanase I (xyn1) gene expression in Trichoderma reesei. 889 95

Elements of the lactose operon were used to study parameters affecting gene expression in cultured cells and transgenic animals. A Lac repressor protein containing a nuclear transport signal was shown to inhibit expression of a reporter gene by interacting with lac operator sequences. In cultured cells, operator sequence, operator placement and induction parameters were all shown to be important for obtaining tight repression of a reporter gene followed by high level expression upon induction. Induction levels were also dependent on the reporter gene, with the luciferase gene yielding higher induction levels than the chloramphenicol acetyltransferase gene. In transgenic animals, the lacI mRNA was not detected in the C57BL/6 mouse strain until the animal was exposed to a demethylating agent. After 5-azacytidine treatment, expression of lacI mRNA was detected in the brain, heart, kidney, lung and ovary. In the FVB transgenic mouse strain, expression of lacI mRNA was detected without 5-azacytidine treatment in the kidney, liver, lung, and testes. Preliminary experiments with double transgenic animals containing both lacI and operator/luciferase transgenes showed a decrease in luciferase expression compared to the luciferase-only animals in both tissue extracts and transgenic fetal primary cultures, although IPTG induction was not achieved in these animals or primary cultures. The applicability and challenges of the system for regulation of gene expression are discussed.
Environ Mol Mutagen 1996
PMID:Parameters affecting the use of the lac repressor system in eukaryotic cells and transgenic animals. 899 Oct 77

Replication of the streptococcal plasmid pLS1 is controlled by two plasmid-encoded gene products: the repressor protein CopG and the antisense RNA, RNA II. Two different mutants in rnaII have been isolated. The 5'-end and the levels of RNA II synthesized by pneumococcal cells harbouring the wild-type pLS1 or mutant plasmids (affected in either genes copG or rnaII) were analysed. One of the rnaII mutants exhibited a high-copy-number phenotype, whereas an in vitro-constructed mutation, which affects the -10 region of the rnaII promoter, resulted in plasmids lacking copy-number phenotype. The latter mutation had a pleiotropic effect: It abolished RNA II synthesis, but it also affected the initiation of translation signals of the gene encoding the RepB initiator protein. Transcriptional and translational fusions, together with in vitro inhibition of RepB synthesis by specific oligonucleotides, showed translational inhibition of RepB synthesis by RNA II, perhaps by directly blocking the accessibility of the ribosomes to the repB initiation of translation signals.
Mol Microbiol 1997 Jan
PMID:Replication control of plasmid pLS1: the antisense RNA II and the compact rnaII region are involved in translational regulation of the initiator RepB synthesis. 900 24


<< Previous 1 2 3 4 5 6 7 8 9 10