SEARCH · PubMed Health

Results for “Translational repression”

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 1,171 records · Page 65Linked to original sources

PubMed2005

A role for phosphorylation in the regulation of the barley scutellar peptide transporter HvPTR1 by amino acids.

Protein reserves in the cereal endosperm are sequentially degraded to small peptides and amino acids during germination and these are translocated across the scutellum to support growth of the embryo. Peptide transport in the germinating barley grain is mediated by specific carriers localized to the plasma membrane of the scutellar epithelium. In isolated barley embryos peptide transport is rapidly inhibited by amino acid concentrations comparable with those found in the post-germination barley grain. However, this inhibition of HvPTR1 activity is not effected at either the transcriptional or translational level. The protein phosphatase inhibitor okadaic acid repressed transport of Ala-[14C]Phe, but not [14C]Ala, into the barley scutellar epithelium. In vivo [32P]orthophosphate labelling studies of barley scutellar tissue in combination with immunoprecipitation studies using antiserum raised to HvPTR1 showed that HvPTR1 (66 kDa) is phosphorylated in the presence of amino acids. Immunopurified HvPTR1 was further demonstrated to be phosphorylated on serine residues. Digestion with the N-glycosidase enzyme PNGase F results in a shift in the molecular mass of the protein by 10 kDa, indicating that HvPTR1 is an N-linked glycoprotein. These results provide strong circumstantial evidence that HvPTR1 peptide transport activity in the germinating barley grain is regulated at the post-translational level by phosphorylation in response to rising levels of amino acids emanating from the endosperm as a result of storage protein breakdown and mobilization. This is potentially an important element in balancing the flux of organic nitrogen and carbon from the endosperm to embryo during germination and seedling establishment.

Amino Acids↗

PubMed2000

The gcvB gene encodes a small untranslated RNA involved in expression of the dipeptide and oligopeptide transport systems in Escherichia coli.

The Escherichia coli gcvB gene encodes a small RNA transcript that is not translated in vivo. Transcription from the gcvB promoter is activated by the GcvA protein and repressed by the GcvR protein, the transcriptional regulators of the gcvTHP operon encoding the enzymes of the glycine cleavage system. A strain carrying a chromosomal deletion of gcvB exhibits normal regulation of gcvTHP expression and glycine cleavage enzyme activity. However, this mutant has high constitutive synthesis of OppA and DppA, the periplasmic-binding protein components of the two major peptide transport systems normally repressed in cells growing in rich medium. The altered regulation of oppA and dppA was also demonstrated using oppA-phoA and dppA-lacZ gene fusions. Although the mechanism(s) involving gcvB in the repression of these two genes is not known, oppA regulation appears to be at the translational level, whereas dppA regulation occurs at the mRNA level.

Base Sequence↗

PubMed2006

Constitutive promoter occupancy by the MBF-1 activator and chromatin modification of the developmental regulated sea urchin alpha-H2A histone gene.

The tandemly repeated sea urchin alpha-histone genes are developmentally regulated. These genes are transcribed up to the early blastula stage and permanently silenced as the embryos approach gastrulation. As previously described, expression of the alpha-H2A gene depends on the binding of the MBF-1 activator to the 5' enhancer, while down-regulation relies on the functional interaction between the 3' sns 5 insulator and the GA repeats located upstream of the enhancer. As persistent MBF-1 binding and enhancer activity are detected in gastrula embryos, we have studied the molecular mechanisms that prevent the bound MBF-1 from trans-activating the H2A promoter at this stage of development. Here we used chromatin immunoprecipitation to demonstrate that MBF-1 occupies its site regardless of the transcriptional state of the H2A gene. In addition, we have mapped two nucleosomes specifically positioned on the enhancer and promoter regions of the repressed H2A gene. Interestingly, insertion of a 26 bp oligonucleotide between the enhancer and the TATA box, led to up-regulation of the H2A gene at gastrula stage, possibly by changing the position of the TATA nucleosome. Finally, we found association of histone de-acetylase and de-acetylation and methylation of K9 of histone H3 on the promoter and insulator of the repressed H2A chromatin. These data argue for a role of a defined positioned nucleosome in the promoter and histone tail post-translational modifications, in the 3' insulator and 5' regulatory regions, in the repression of the alpha-H2A gene despite the presence of the MBF-1 activator bound to the enhancer.

Animals↗

PubMed1983

Post-transcriptional control of expression of the repA gene of plasmid R1 mediated by a small RNA molecule.

Fusions between the repA gene of plasmid R1 (required for autonomous plasmid replication) and the lac genes have been the basis for in vivo studies of regulation of repA expression. Two gene products--the CopA RNA and the CopB protein--act as inhibitors of repA expression. Comparison of the effects of addition in trans of the two Cop functions on transcription and translation of repA-lac gene fusions show that the CopB protein represses transcription of the repA gene, whereas the CopA RNA interferes with the RepA mRNA in such a way that effective translation is inhibited. The CopA RNA does not seem to have a direct effect on the transcription of the repA gene but, as a consequence of the posttranscriptional regulation, transcriptional polarity within the repA gene is observed. It is also shown that the CopA RNA interacts with its target (CopT) only when the region is transcribed to form RepA mRNA.

Artificial Gene Fusion↗

PubMed2004

Influence of catabolite repression and inducer exclusion on the bistable behavior of the lac operon.

A mathematical model of the lac operon which includes all of the known regulatory mechanisms, including external-glucose-dependent catabolite repression and inducer exclusion, as well as the time delays inherent to transcription and translation, is presented. With this model we investigate the influence of external glucose, by means of catabolite repression and the regulation of lactose uptake, on the bistable behavior of this system.

Catalysis↗

PubMed1994

Post-transcriptional regulation of the str operon in Escherichia coli. Ribosomal protein S7 inhibits coupled translation of S7 but not its independent translation.

The str operon of Escherichia coli consists of the genes for ribosomal proteins S12 (rpsL) and S7 (rpsG) and elongation factors G (fusA) and Tu (tufA). Previous studies have shown that S7 is a translational feedback repressor and inhibits the synthesis of itself and of elongation factor G. We have now shown that induction of S7 synthesis from the S7 gene fused to the arabinose promoter on a plasmid also leads to inhibition of the synthesis of S12 from the chromosomal S12 gene, and that this regulation takes place using the same target site as that used for distal gene regulation, i.e. S7 retroregulates S12. We have then demonstrated that S7 synthesis is mostly translationally coupled with the translation of the preceding S12 gene. Using a rpsG'-'lacZ fusion gene as a reporter for S7 synthesis, we found that abolishing S12 translation by a mutational alteration of the AUG start codon of the S12 gene leads to about tenfold reduction of S7 synthesis without significantly affecting its rate of transcription. Deletion of the proximal portion of the S12 gene or a premature termination of S12 translation by an amber mutation at the 26th codon also led to a large reduction of S7 synthesis. Unexpectedly, we have discovered that overproduction of S7 in trans from a plasmid leads to repression of the rpsG'-'lacZ fusion gene when the fusion gene is preceded by the intact S12 gene, but not when the S12 gene carried the above-mentioned mutations that abolish S12 translation. Thus, a novel feature of this regulatory system is that translation of S7 achieved by independent initiation is not inhibited by S7 in vivo, whereas translation of S7 achieved by translational coupling is sensitive to S7 repression. These observations also suggest that the coupled S7 translation is probably achieved by the use of ribosomal subunits employed for translation of the upstream S12 gene.

Arabinose↗

PubMed2006

Doxorubicin down-regulates Kruppel-associated box domain-associated protein 1 sumoylation that relieves its transcription repression on p21WAF1/CIP1 in breast cancer MCF-7 cells.

The role of post-translational modification, such as sumoylation, in modulating the efficacy of doxorubicin (Dox) treatment remains unclear. Transcriptional cofactor KRAB domain-associated protein 1 (KAP1) has been shown to complex with the KRAB zinc finger protein, ZBRK1, to repress the transcription of target genes. Through a combination of proteomic screening and site-directed mutagenesis approaches, we have identified lysines 554, 779, and 804 as the major sumoylation sites in KAP1. We then present evidence that Dox-mediated induction of cell cycle regulator p21 expression is differentially regulated by KAP1 sumoylation status. Moreover, the KAP1 sumoylation level was transiently decreased upon Dox exposure, and transfection with the KAP1 sumoylation mimetic, SUMO-1-KAP1, desensitizes breast cancer MCF-7 cells to Dox-elicited cell death. The sumoylation-dependent stimulation of KAP1 function is achieved by enhancing the methylation of H3-K9 and attenuating the acetylation of H3-K9 and H3-K14 at the p21 core promoter. We also show that occupancy of ZBRK1 response elements located at the p21 promoter by ZBRK1.KAP1 is independent of KAP1 sumoylation. Hence, sumoylation of KAP1 represses p21 transcription via a chromatin-silencing process without affecting interaction between KAP1.ZBRK1 and DNA, thus providing a novel mechanistic basis for the understanding of Dox-induced de-repression of p21 transcription. Taken together, our results suggest that Dox-induced decrease in KAP1 sumoylation is essential for Dox to induce p21 expression and subsequent cell growth inhibition in MCF-7 cells.

Antibiotics, Antineoplastic↗

PubMed2003

Splicing regulation: the cell cycle connection.

Many genes are repressed during mitosis, and this is known to involve differential phosphorylation of specific factors required for transcription, 3'-end RNA processing and translation. A recent study suggests that splicing is also targeted for mitotic repression, in this case by dephosphorylation of the newly identified splicing factor SRp38.

Cell Cycle↗

PubMed2004

Modification of de novo DNA methyltransferase 3a (Dnmt3a) by SUMO-1 modulates its interaction with histone deacetylases (HDACs) and its capacity to repress transcription.

The de novo DNA methyltransferase Dnmt3a is one of three mammalian DNA methyltransferases that has been shown to play crucial roles in embryonic development, genomic imprinting and transcriptional silencing. Despite its importance, very little is known about how the enzymatic activity and transcriptional repression functions of Dnmt3a are regulated. Here we show that Dnmt3a interacts with multiple components of the sumoylation machinery, namely the E2 sumo conjugating enzyme Ubc9 and the E3 sumo ligases PIAS1 and PIASxalpha, all of which are involved in conjugating the small ubiquitin-like modifier polypeptide, SUMO-1, to its target proteins. Dnmt3a is modified by SUMO-1 in vivo and in vitro and the region of Dnmt3a responsible for interaction maps to the N-terminal regulatory domain. Functionally, sumoylation of Dnmt3a disrupts its ability to interact with histone deacetylases (HDAC1/2), but not with another interaction partner, Dnmt3b. Conditions that enhance the sumoylation of Dnmt3a in vivo abolish its capacity to repress transcription. These studies reveal a new level of regulation governing Dnmt3a whereby a post-translational modification can dramatically regulate its interaction with specific protein partners and alter its ability to repress transcription.

Animals↗

PubMed1987

AUU-to-AUG mutation in the initiator codon of the translation initiation factor IF3 abolishes translational autocontrol of its own gene (infC) in vivo.

We previously showed that Escherichia coli translation initiation factor IF3 regulates the expression of its own gene infC at the translational level in vivo. Here we create two alterations in the infC gene and test their effects on translational autocontrol of infC expression in vivo by measuring beta-galactosidase activity expressed from infC-lacZ gene fusions under conditions of up to 4-fold derepression or 3-fold repression of infC expression. Replacement of the infC promoter with the trp promoter deletes 120 nucleotides of the infC mRNA 5' to the translation initiation site without affecting autogenous translational control. Mutation of the unusual AUU initiator codon of infC to the more common AUG initiator codon abolishes translation initiation factor IF3-dependent repression and derepression of infC expression in vivo. These results establish the AUU initiator codon of infC as an essential cis-acting element in autogenous translational control of translation initiation factor IF3 expression in vivo.

Bacteriophage lambda↗

PubMed1984

Regulation of biosynthesis of the rat liver inner mitochondrial membrane by thyroid hormone.

Regulation of mitochondrial protein synthesis by thyroid hormone has been studied in isolated rat hepatocytes and liver mitochondria. Small doses (5 micrograms/100 g body wt) of triiodothyronine (T3) injected into hypothyroid rats increased both state 3 and 4 respiration by approximately 100%, while the ADP:O ratio remained constant. This suggests that T3 increases the numbers of functional respiratory chain units. T3 also induces mitochondrial protein synthesis by 50-100%. Analysis of the mitochondrial translation products show that all of the products were induced. No differential translation of the peptides involved in the respiratory chain was found. Regulation of the cytoplasmically made inner membrane peptides was also investigated in isolated hepatocytes. The majority of these peptides were not influenced by T3, in contrast to the finding with mitochondrial translation products. Those found to be regulated by T3 belong to two subsets, which were either induced or repressed by hormone. Thus, T3 stimulated a general increase in the synthesis of mitochondrially translated inner membrane peptides, but regulates selectively those inner membrane peptides translated on cytoplasmic ribosomes. The findings suggest that hormone regulation of the respiratory chain is exerted through a few selective proteins, perhaps those which require subunits made from both nuclear and mitochondrial genes.

Animals↗

PubMed2002

Translational feedback regulation of the gene for L35 in Escherichia coli requires binding of ribosomal protein L20 to two sites in its leader mRNA: a possible case of ribosomal RNA-messenger RNA molecular mimicry.

In addition to being a component of the large ribosomal subunit, ribosomal protein L20 of Escherichia coli also acts as a translational repressor. L20 is synthesized from the IF3 operon that contains three cistrons coding for IF3, and ribosomal proteins L35 and L20. L20 directly represses the expression of the gene encoding L35 and the expression of its own gene by translational coupling. All of the cis-acting sequences required for repression by L20, called the operator, are found on an mRNA segment extending from the middle of the IF3 gene to the start of the L35 gene. L20-mediated repression requires a long-range base-pairing interaction between nucleotide residues within the IF3 gene and residues just upstream of the L35 gene. This interaction results in the formation of a pseudoknot. Here we show that L20 causes protection of nucleotide residues in two regions of the operator in vitro. The first region is the pseudoknot itself and the second lies in an irregular stem located upstream of the L35 gene. By primer extension analysis, we show that L20 specifically induces reverse transcriptase stops in both regions. Therefore, these two regions define two L20-binding sites in the operator. Using mutations and deletions of rpml'-'lacZ fusions, we show that both sites are essential for repression in vivo. However L20 can bind to each site independently in vitro. One site is similar to the L20-binding site on 23S rRNA. Here we propose that L20 recognizes its mRNA and its rRNA in similar way.

5' Untranslated Regions↗

PubMed2002

Snf1 protein kinase regulates Adr1 binding to chromatin but not transcription activation.

The yeast transcriptional activator Adr1 controls the expression of genes required for ethanol, glycerol, and fatty acid utilization. We show that Adr1 acts directly on the promoters of ADH2, ACS1, GUT1, CTA1, and POT1 using chromatin immunoprecipitation assays. The yeast homolog of the AMP-activated protein kinase, Snf1, promotes Adr1 chromatin binding in the absence of glucose, and the protein phosphatase complex, Glc7.Reg1, represses its binding in the presence of glucose. A post-translational process is implicated in the regulation of Adr1 binding activity. Chromatin binding by Adr1 is not the only step in ADH2 transcription that is regulated by glucose repression. Adr1 can bind to chromatin in repressed conditions in the presence of hyperacetylated histones. To study steps subsequent to promoter binding we utilized miniAdr1 transcription factors to characterize Adr1-dependent transcription in vitro. Yeast nuclear extracts prepared from glucose-repressed and glucose-derepressed cells are equally capable of supporting miniAdr1-dependent transcription and pre-initiation complex formation. Nuclear extracts prepared from a snf1 mutant support miniAdr1-dependent transcription but are partially defective in the formation of pre-initiation complexes with Mediator components being particularly depleted. We conclude that Snf1 regulates Adr1-dependent transcription primarily at the level of chromatin binding.

Chromatin↗

PubMed1996

Synthesis of the beta and beta' subunits of Escherichia coli RNA polymerase is autogenously regulated in vivo by both transcriptional and translational mechanisms.

Numerous experiments have indicated that the synthesis of RNA polymerase (beta beta' alpha 2 sigma 70) in Escherichia coli is autogenously regulated. In the present study, we have examined expression of the rpoB and rpoC genes which encode the beta and beta' subunits of RNA polymerase. These genes are the distal cistrons of the rplKAJLrpoBC ribosomal protein-RNA polymerase transcription unit. Both transcriptional (operon) and translational (gene) fusions of either rpoB or rpoC to the lacZ reporter were used to monitor their in vivo expression by inserting single copies of these fusions into the bacterial chromosome on integration-proficient lambda vectors. In order to examine the expression of the rpoBC genes in response to varied intracellular concentrations of the RNA polymerase subunits, a series of expression plasmids carrying the rpoB, rpoC, rpoA (alpha) and rpoD (sigma 70) genes in different combinations were then introduced into these cells. Elevated concentrations of either beta or beta' were found to repress the expression of both rpoB and rpoC at the translational level. However, the simultaneous increase in the concentration of all the subunits that comprise holoenzyme repressed the transcription of rpoBC. To determine the site of this repression, additional operon fusions were utilized which placed lacZ downstream of each of the transcriptional regulatory sites of this gene cluster, including two promoters, rplKp and rplJp, and a transcriptional attenuator in the rplL-rpoB intercistronic region. Expression from these fusions showed that transcriptional repression is achieved primarily by reducing initiation at both upstream promoters, coupled with a small increase in termination at the attenuator.

DNA-Directed RNA Polymerases↗

PubMed2003

Tetracycline-aptamer-mediated translational regulation in yeast.

We describe post-transcriptional gene regulation in yeast based on direct RNA-ligand interaction. Tetracycline-dependent translational regulation could be imposed via specific aptamers inserted at two different positions in the 5' untranslated region (5'UTR). Translation in vivo was suppressed up to ninefold upon addition of tetracycline. Repression via an aptamer located near the start codon (cap-distal) in the 5'UTR was more effective than repression via a cap-proximal position. On the other hand, suppression in a cell-free system reached maximally 50-fold and was most effective via a cap-proximal aptamer. Examination of the kinetics of tetracycline-dependent translational inhibition in vitro revealed that preincubation of tetracycline and mRNA before starting translation led not only to the fastest onset of inhibition but also the most effective repression. The differences between the behaviour of the regulatory system in vivo and in vitro are likely to be related to distinct properties of mRNP structure and mRNA accessibility in intact cells as opposed to cell-extracts. Tetracycline-dependent regulation was also observed after insertion of an uORF sequence upstream of the aptamer, indicating that our system also targets reinitiating ribosomes. Polysomal gradient analyses provided insight into the mechanism of regulation. Cap-proximal insertion inhibits binding of the 43S complex to the cap structure whereas start-codon-proximal aptamers interfere with formation of the 80S ribosome, probably by blocking the scanning preinitiation complex.

5' Untranslated Regions↗

PubMed1985

Differential efficiencies of in vitro translation of mouse c-myc transcripts differing in the 5' untranslated region.

We have studied the in vitro translational efficiencies of two murine c-myc transcripts synthesized in vitro that differ in the lengths of their 5' noncoding regions (448 and 83 nucleotides) and also in their 3' noncoding regions. When translated in a reticulocyte translation system, the shorter transcript was translated 10-fold more efficiently. These results are consistent with the hypothesis of Saito et al. [Saito, H., Hayday, A. C., Wiman, K., Hayward, W. S. & Tonegawa, S. (1983) Proc. Natl. Acad. Sci. USA 80, 7476-7480] that translation of full-length human c-myc mRNA is normally repressed, whereas in several Burkitt lymphomas that have deletions of the mRNA 5' noncoding region (resulting from translocation of the c-myc gene), translation of the c-myc mRNA is more efficient. Our results suggest that activation of murine c-myc expression by production of a more efficient mRNA might in some cases play a role in neoplastic transformation.

Animals↗

PubMed1995

The transcriptional regulatory protein, YB-1, promotes single-stranded regions in the DRA promoter.

YB-1 is a member of a newly defined family of DNA- and RNA-binding proteins, the Y box factors. These proteins have been shown to affect gene expression at both the transcriptional and translational levels. Recently, we showed that YB-1 represses interferon-gamma-induced transcription of class II human major histocompatibility (MHC) genes (1). Studies in this report characterize the DNA binding properties of purified, recombinant YB-1 on the MHC class II DRA promoter. The generation of YB-1-specific antibodies further permitted an analysis of the DNA binding properties of endogenous YB-1. YB-1 specifically binds single-stranded templates of the DRA promoter with greater affinity than double-stranded templates. The single-stranded DNA binding sites of YB-1 were mapped to the X box, whereas the double-stranded binding sites were mapped to the Y box of the DRA promoter, by methylation interference analysis. Most significantly, YB-1 can induce or stabilize single-stranded regions in the X and Y elements of the DRA promoter, as revealed by mung bean nuclease analysis. In concert with the findings that YB-1 represses DRA transcription, this study of YB-1 binding properties suggests a model of repression in which YB-1 binding results in single-stranded regions within the promoter, thus preventing loading and/or function of other DRA-specific transactivating factors.

Base Sequence↗

PubMed1986

Luteinization-specific ovarian mitochondrial proteins.

Mitochondria isolated from porcine medium- and large-sized ovarian follicles and corpora lutea show progressive increases in specific proteins temporally associated with luteinization. These include 12-15, 16-17, 33, 47, 50, and 60 kDa proteins. Synthesis of these same mitochondrial proteins is stimulated by incubation of large ovarian follicles with luteinizing hormone (LH) (0.10 microgram/ml) but not by follicle-stimulating hormone (0.10 microgram/ml). A dose-response curve was generated indicating that synthesis of several mitochondrial proteins is stimulated in an LH-dependent manner, while synthesis of two appear to be repressed (70 and 94 kDa). Examination of mitochondrial translation products (cycloheximide-insensitive, chloramphenicol-sensitive protein synthesis) from isolated follicular and luteal mitochondria, by both one- and two-dimensional electrophoresis, demonstrated that two proteins (23 and 35 kDa) are synthesized within luteal but not follicular mitochondria. Further, synthesis of two proteins within follicular mitochondria are significantly reduced in luteal mitochondrial. Regulation of mitochondrial proteins necessary for the rate-limiting step in steroidogenesis is discussed.

Animals↗