SEARCH · PubMed Health

Results for “Translational control”

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 181 records · Page 10Linked to original sources

PubMed1990

cis-acting sequences involved in the translational control of GCN4 expression.

Four short upstream open reading frames (uORFs) in the mRNA leader are required for the translational control of GCN4 expression in response to amino acid availability. Data are reviewed demonstrating that the fourth (3' proximal) uORF is sufficient to establish the repressed levels of GCN4 expression, while the first uORF functions as a positive regulatory element under starvation conditions to stimulate GCN4 translation. Furthermore, positive and negative trans-acting regulatory factors, the activities of which appear to be modulated according to amino acid availability, exert their effects on GCN4 expression through the uORFs. Direct comparison of the uORFs indicates that there are important nucleotide sequence differences between uORF1 and 4, and that these are located primarily around the termination codons of these elements. Recent findings suggest that the sequences that mediate repression of GCN4 expression are complex, but can be overcome under starvation conditions by ribosomes that have previously translated uORF1.

Alleles↗

PubMed2001

Temporal translational control by a metastable RNA structure.

Programmed cell death by the hok/sok locus of plasmid R1 relies on a complex translational control mechanism. The highly stable hok mRNA is activated by 3'-end exonucleolytical processing. Removal of the mRNA 3' end releases a 5'-end sequence that triggers refolding of the mRNA. The refolded hok mRNA is translatable but can also bind the inhibitory Sok antisense RNA. Binding of Sok RNA leads to irreversible mRNA inactivation by an RNase III-dependent mechanism. A coherent model predicts that during transcription hok mRNA must be refractory to translation and antisense RNA binding. Here we provide genetic evidence for the existence of a 5' metastable structure in hok mRNA that locks the nascent transcript in an inactive configuration in vivo. Consistently, the metastable structure reduces the rate of Sok RNA binding and completely blocks hok translation in vitro. Structural analyses of native RNAs strongly support that the 5' metastable structure exists in the nascent transcript. Further structural analyses reveal that the mRNA 3' end triggers refolding of the mRNA 5' end into the more stable tac-stem conformation. These results provide a profound understanding of an unusual and intricate post-transcriptional control mechanism.

Bacterial Proteins↗

PubMed1997

Translational control of terminal oligopyrimidine mRNAs requires a specific regulator.

Terminal oligopyrimidine (TOP) mRNAs are a group of messengers translationally regulated according to the growth status of the cell. Two hypotheses have been proposed for the mechanism of the regulation: (i) there is a specific translational regulator which can reversibly alter TOP-mRNA structure, (ii) a component of the general translational apparatus can specifically affect the translation of TOP-mRNAs. To verify one of the two hypotheses we induced a partial inhibition of translation initiation in Xenopus cultured cells and analyzed the effect on TOP-mRNA translation. Our results suggest that a specific regulator is necessary to explain the translational control of these of mRNAs.

Animals↗

PubMed2006

Translationally controlled tumor protein from Madurella mycetomatis, a marker for tumorous mycetoma progression.

About 40 years ago Abs against the fungus Madurella mycetomatis were first demonstrated to be present in eumycetoma patients, a disease characterized by tumorous swellings. To date nothing is known about the individual immunoreactive Ags present in this fungus. In the present study, we identify its first immunogenic Ag, a protein homologous to the translationally controlled tumor protein (TCTP), a well-conserved histamine release factor in a range of eukaryotes. The gene for this Ag was demonstrated to be present in two variants in M. mycetomatis, with 13% aa difference between the two proteins encoded. In vitro, TCTP was secreted into the culture medium. In vivo, it was found to be expressed on hyphae present in developing stages of the eumycetoma-characteristic black grain. Significant IgG and IgM immune responses, against the whole protein and selected M. mycetomatis-specific peptides, were determined. The Ab levels correlated with lesion size and disease duration. Overall, the patients with the largest lesions had the highest Ab level, which lowered with decreasing size of the lesion. After 6-15 years of disease duration the Ab levels were the highest. TCTP is the first well-characterized immunogenic Ag, simultaneously the first monomolecular vaccine candidate, identified for the fungus M. mycetomatis.

Adult↗

PubMed1987

A segment of GCN4 mRNA containing the upstream AUG codons confers translational control upon a heterologous yeast transcript.

GCN4 encodes a transcriptional activator in Saccharomyces cerevisiae that is regulated at the translational level. We show that an approximately 240-nucleotide segment from the GCN4 mRNA leader containing four AUG codons is sufficient to confer translational control typical of GCN4 upon a GAL1-lacZ fusion transcript. Regulation of the hybrid transcript is dependent upon multiple positive (GCN) and negative (GCD) trans-acting factors shown to regulate GCN4 expression post-transcriptionally. This result limits the target sequences for these factors to a small internal segment of the GCN4 mRNA leader. The elimination of AUG codons within this segment substantially reduces the usual derepressing effect of mutations in five GCD genes upon GCN4-lacZ expression. This supports the idea that the products of these negative regulatory genes act by modulating the effects of the upstream AUG codons on translation of GCN4 mRNA.

Base Sequence↗

PubMed2000

Transcription-coupled translation control of AML1/RUNX1 is mediated by cap- and internal ribosome entry site-dependent mechanisms.

AML1/RUNX1 belongs to the runt domain transcription factors that are important regulators of hematopoiesis and osteogenesis. Expression of AML1 is regulated at the level of transcription by two promoters, distal (D) and proximal (P), that give rise to mRNAs bearing two distinct 5' untranslated regions (5'UTRs) (D-UTR and P-UTR). Here we show that these 5'UTRs act as translation regulators in vivo. AML1 mRNAs bearing the uncommonly long (1,631-bp) P-UTR are poorly translated, whereas those with the shorter (452-bp) D-UTR are readily translated. The low translational efficiency of the P-UTR is attributed to its length and the cis-acting elements along it. Transfections and in vitro assays with bicistronic constructs demonstrate that the D-UTR mediates cap-dependent translation whereas the P-UTR mediates cap-independent translation and contains a functional internal ribosome entry site (IRES). The IRES-containing bicistronic constructs are more active in hematopoietic cell lines that normally express the P-UTR-containing mRNAs. Furthermore, we show that the IRES-dependent translation increases during megakaryocytic differentiation but not during erythroid differentiation, of K562 cells. These results strongly suggest that the function of the P-UTR IRES-dependent translation in vivo is to tightly regulate the translation of AML1 mRNAs. The data show that AML1 expression is regulated through usage of alternative promoters coupled with IRES-mediated translation control. This IRES-mediated translation regulation adds an important new dimension to the fine-tuned control of AML1 expression.

5' Untranslated Regions↗

PubMed2004

Molecular cloning and expression of a mammalian homologue of a translationally controlled tumor protein (TCTP) gene from Penaeus monodon shrimp.

White spot syndrome, caused by white spot syndrome virus (WSSV), is a deadly disease of shrimps, causing a catastrophic loss in shrimp industries worldwide. In order to investigate molecular response of shrimp haemocyte to WSSV infection, we performed subtraction hybridization of mRNAs from healthy and WSSV-infected haemocyte. One of the genes that were severely down-regulated in moribund WSSV-infected-haemocyte was translationally controlled tumor protein (TCTP) (or fortilin). Strikingly, while there was a slight difference in the amount of TCTP message between normal and early WSSV-infected shrimps, shrimps that exhibited severe symptoms uniformly had very little TCTP in their haemocyte. Taken together with the fact that TCTP functions as an anti-apoptotic protein in mammals, our data suggest that TCTP in shrimp protects WSSV-infected shrimps from death.

Amino Acid Sequence↗

PubMed2003

A Mg2+-dependent RNA tertiary structure forms in the Bacillus subtilis trp operon leader transcript and appears to interfere with trpE translation control by inhibiting TRAP binding.

Expression of the trpEDCFBA operon of Bacillus subtilis is regulated by transcription attenuation and translation control mechanisms. In each case, binding of the trp RNA-binding attenuation protein (TRAP) to the untranslated trp leader transcript mediates conformational changes in the RNA secondary structure. We examined the structure of the trp leader readthrough RNA in the absence of TRAP. Using chemical and enzymatic probes, the secondary structure of the trp leader RNA was found to be similar to predicted models. In addition, this RNA was found to adopt a Mg(2+)-dependent, long-range tertiary interaction under physiological monovalent salt conditions. Formation of this tertiary structure does not require significant changes in the preformed secondary structure. Enzymatic probing of the RNA in the presence of competitor DNA oligonucleotides that were designed to disrupt the predicted tertiary structure allowed identification of the interacting partners as the single-stranded portion of the purine-rich TRAP binding target and a large downstream pyrimidine-rich internal loop. UV cross-linking experiments utilizing 5'-p-azidophenacyl-containing transcripts revealed a Mg(2+)-dependent cross-link. Mapping of this cross-link provided evidence that the single-stranded segment of the TRAP binding site is in close proximity to the internal loop. Results from UV melting experiments with wild-type and mutant trp leader transcripts suggested a likely base-pairing register for the tertiary structure. Filter-binding studies demonstrated that the addition of Mg(2+) inhibits TRAP binding, which may be partially due to the effect of Mg(2+) on RNA tertiary structure formation. Results from expression studies using trpE'-'lacZ translational fusions and RNA-directed cell-free translation experiments suggest that the Mg(2+)-dependent tertiary structure inhibits TRAP's ability to regulate translation of trpE.

Bacillus subtilis↗

PubMed1981

Cytoplasmic nonpolysomal ribonucleoprotein complexes and translational control.

In this article, we discuss our attempts to establish the existence in the cytoplasm of regulatory molecules involved in translational control. Our studies have revealed the presence of cAMP independent protein kinase in the free mRNP complex capable of phosphorylating a Mr = 38 000 polypeptide, also part of the same complex. Both the kinase and the acceptor protein were found also as free proteins in the cytoplasmic pool. This kinase has been shown to be distinct from the heme regulated enzyme that phosphorylates the small subunit of eIF-2. Other regulatory molecules include small molecular weight RNAs found as part of an RNP complex. A 4S fraction isolated from this complex inhibited the translation of both capped and uncapped mRNAs in a cell-free protein synthesizing system. The biological role of the protein kinase and the 4S RNA fraction is considered.

Animals↗

PubMed1999

Expression of translationally controlled tumour protein is regulated by calcium at both the transcriptional and post-transcriptional level.

We have investigated how the programme of protein synthesis is altered in response to a loss of calcium homoeostasis in Cos-7 cells using a differential proteome mapping approach. Exposure of the cells to the calcium ionophore A23187 or thapsigargin, or alternatively, expression of a viral glycoprotein reported to deplete intracellular calcium stores, resulted in the up-regulated expression of a characteristic set of proteins. One of these is the translationally controlled tumour protein (TCTP), a cytoplasmic protein whose expression has not previously been linked to calcium perturbation. Quantitative Northern blot assay demonstrated that steady-state mRNA abundance of TCTP was also increased under these conditions. Clamping the cytosolic calcium concentration by the introduction of bis-(o-aminophenoxy)-ethane-N,N,N',N'-tetra-acetic acid (BAPTA) into cells did not affect the increase in steady-state levels of TCTP mRNA observed in response to ionophore. Therefore depletion of endoplasmic reticulum (ER) calcium, but not elevation of the cytosolic calcium concentration, was responsible for increased transcription of the TCTP gene. However, the presence of BAPTA significantly attenuated the ionophore-mediated increase in levels of the protein. Moreover, the level of TCTP in ionophore-treated cells increased in advance of a detectable increase in the corresponding mRNA abundance. These results indicate that expression of TCTP is regulated at two distinct levels in response to the concentration of calcium in different cellular compartments. Whereas depletion of the ER store causes an increase in TCTP mRNA abundance, increased cytosolic calcium concentrations regulate gene expression at the post-transcriptional level.

Animals↗

PubMed1997

DNA transfection to study translational control in mammalian cells.

Mammalian cells respond to changes in their environment by rapid and reversible covalent modification of the translational machinery. In most cases, these modifications involve the phosphorylation and dephosphorylation of translation initiation factors (for review see Ref. 1). The modification of translation initiation factors may affect translational activity of either specific mRNAs or general cellular mRNAs. To study the effect of a particular factor or its modification on the translational capacity of an mRNA, there are a number of potential approaches that include in vitro translation reactions as well as in vivo experiments. Generally, experiments initially report a covalent modification that correlates with altered translational capacity of either a specific or a general class of mRNAs. The modification and the particular amino acid residue involved are then identified. Then mutations are made at the modified residue to prevent modification (for example, a serine-to-alanine mutation to prevent phosphorylation) and the effect of the mutant factor on the translation of a target mRNA is tested. The most convenient method for monitoring the effect of a mutant translation factor on translation is the use of transient DNA transfection. However, in certain situations it is desirable to isolate stably transfected cell lines to study the effect of overexpression, underexpression, or expression of a particular mutant translation factor. This article reviews two methods that are routinely used to study translational control that involve either transient or stable DNA transfection.

Animals↗

PubMed2004

Study of translational control of eukaryotic gene expression using yeast.

Eukaryotic cells respond to starvation by decreasing the rate of general protein synthesis while inducing translation of specific mRNAs encoding transcription factors GCN4 (yeast) or ATF4 (humans). Both responses are elicited by phosphorylation of translation initiation factor 2 (eIF2) and the attendant inhibition of its nucleotide exchange factor eIF2B-decreasing the binding to 40S ribosomes of methionyl initiator tRNA in the ternary complex (TC) with eIF2 and GTP. The reduction in TC levels enables scanning ribosomes to bypass the start codons of upstream open reading frames in the GCN4 mRNA leader and initiate translation at the authentic GCN4 start codon. We exploited the fact that GCN4 translation is a sensitive reporter of defects in TC recruitment to identify the catalytic and regulatory subunits of eIF2B. More recently, we implicated the C-terminal domain of eIF1A in 40S-binding of TC in vivo. Interestingly, we found that TC resides in a multifactor complex (MFC) with eIF3, eIF1, and the GTPase-activating protein for eIF2, known as eIF5. Our biochemical and genetic analyses indicate that physical interactions between MFC components enhance TC binding to 40S subunits and are required for wild-type translational control of GCN4. MFC integrity and eIF3 function also contribute to post-assembly steps in the initiation pathway that impact GCN4 expression. Thus, apart from its critical role in the starvation response, GCN4 regulation is a valuable tool for dissecting the contributions of multiple translation factors in the eukaryotic initiation pathway.

DNA-Binding Proteins↗

PubMed2002

A high-efficiency translational control element with potential for cancer gene therapy.

An active internal ribosome entry sequence (IRES) that efficiently mediates cap (m7pppGN)-independent translation in human carcinoma cells could be an effective device for gene co-transduction in cancer gene therapy. In this study using the cytomegalovirus (CMV) promoter, a remarkable internal translation activity was observed and mediated by the sequence localized to the 183-653 region of 5' NF-kappaB repressor mRNA (NFR183IRES). To test the potential of such sequence for therapeutic application, we carried out in vitro functional assays using the dicistronic constructs that internally expressed human PTEN tumor suppressor. The PTEN expression mediated by NFR183IRES was found to result in growth inhibition of carcinoma cells more effectively than the expression by NFR1IRES that contained the 1-653 region. When compared to the internal translation driven by the picornaviral IRES element of the encephalomyocarditis virus (EMCV) or the foot-and-mouth disease virus (FMDV), NFR183IRES consistently exhibited a higher activity in the human carcinoma cells, HeLa, LNCaP and MCF7. Such high-efficiency translational control element may prove useful for cancer gene therapy.

5' Untranslated Regions↗

PubMed2000

Translational control of the antiapoptotic function of Ras.

Activated Ras has been shown to provide powerful antiapoptotic signals to cells through well defined transcriptional and post- translational pathways, whereas translational control as a mechanism of Ras survival signaling remains unexplored. Here we show a direct relationship between assembly of the cap-dependent translation initiation apparatus and suppression of apoptosis by oncogenic Ras in vitro and in vivo. Decreasing protein synthesis with rapamycin, which is known to inhibit cap-dependent translation, increases the susceptibility of Ras-transformed fibroblasts to cytostatic drug-induced apoptosis. In contrast, suppressing global protein synthesis with equipotent concentrations of cycloheximide actually prevents apoptosis. Enforced expression of the cap-dependent translational repressor, the eukaryotic translation initiation factor (eIF) 4E-binding protein (4E-BPI), sensitizes fibroblasts to apoptosis in a manner strictly dependent on its ability to sequester eIF4E from a translationally active complex with eIF4GI and the co-expression of oncogenic Ras. Ectopic expression of 4E-BP1 also promotes apoptosis of Ras-transformed cells injected into immunodeficient mice and markedly diminishes their tumorigenicity. These results establish that eIF4E-dependent protein synthesis is essential for survival of fibroblasts bearing oncogenic Ras and support the concept that activation of cap-dependent translation by extracellular ligands or intrinsic survival signaling molecules suppresses apoptosis, whereas synthesis of proteins mediating apoptosis can occur independently of the cap.

Adaptor Proteins, Signal Transducing↗

PubMed2002

The mRNA of the translationally controlled tumor protein P23/TCTP is a highly structured RNA, which activates the dsRNA-dependent protein kinase PKR.

The dsRNA-activated protein kinase PKR is involved in signal transduction pathways that mediate cellular processes as diverse as cell growth and differentiation, the stress response, and apoptosis. PKR was originally described as an interferon-inducible elF2alpha kinase involved in the antiviral defense mechanism of the cell. The interaction of the kinase with specific viral RNAs has been studied in much detail, but information about cellular mRNAs, which are able to bind and activate PKR, is scarce. In search for such cellular mRNAs, we developed a cloning strategy to identify individual mRNA species from the dsRNA-rich fraction of Daudi cell poly(A)+ RNA. Two out of five cDNA clones we obtained contained sequences derived from the mRNA of the translationally controlled tumor protein P23/TCTP, indicating that this mRNA is present in the dsRNA-rich fraction. Secondary structure predictions and gel electrophoretic mobility investigations on P23/TCTP transcripts confirmed the potential of this mRNA to form extensive secondary structure. A full-length P23 transcript, but not a truncated version thereof, was able to bind to PKR in vitro and in vivo. Transient transfection experiments in human 293 cells showed that coexpression of full-length P23 mRNA leads to partial inhibition of the expression of a beta-galactosidase reporter gene in trans. Additional coexpression of a dominant negative mutant of PKR or of adenovirus VA1 RNA suppressed this inhibition, indicating that it is mediated by PKR. Studies on P23/TCTP expression in cells from PKR-knockout mice suggest that P23/TCTP mRNA translation is regulated by PKR. Hence, our results demonstrate that the mRNA of P23/TCTP may both activate PKR and be subject to translational regulation by this kinase.

Animals↗

PubMed1982

Effect of concentration of potassium salts on the activity of the N-ethylmaleimide-treated hemin-controlled translational inhibitor.

The effect of various concentrations of potassium salts on the activity of the N-ethylmaleimide(NEM)-treated hemin-controlled translational inhibitor (HCI) was investigated using the rabbit reticulocyte lysate system. The NEM-treated HCI was found to be less active for the inhibition of globin synthesis at higher concentrations of potassium salts. In addition, the binding of [35S]Met-tRNAf to the 40S ribosomal subunits was inhibited more profoundly at 100 mM than at 240 mM KOAc. The phosphorylation of the NEM-treated HCI and eukaryotic initiation factor, eIF-2, was studied at various concentrations of KOAc. The NEM-treated HCI was phosphorylated to an almost constant extent at 20 to 300 mM K+, but the phosphorylation of eIF-2 alpha by the inhibitor decreased with increasing concentration of KOAc. It was also found that the incubation of the 32P-labeled inhibitor with eIF-2 did not produce the 32P-labeled eIF-2. In the light of these data, a possible relationship between the phosphorylation of the inhibitor or eIF-2 alpha and the inhibition of globin synthesis by the inhibitor is discussed.

Animals↗

PubMed1985

Specific phosphorylation of pig liver initiation factor eIF-2 by the N-ethylmaleimide-treated hemin-controlled translational inhibitor.

The specific phosphorylation of pig liver initiation factor 2(eIF-2) by the N-ethylmaleimide (NEM)-treated hemin-controlled translational inhibitor (HCI) from rabbit reticulocytes was investigated. The inhibitor phosphorylated the serine residue of the alpha subunit of eIF-2 (eIF-2 alpha) and 1 mol of phosphate was incorporated into 1 mol of eIF-2 alpha by the inhibitor on maximal phosphorylation, even when eIF-2 was pretreated with alkaline phosphatase prior to phosphorylation. The 32P-labeled eIF-2 alpha was subjected to tryptic digestion and the tryptic digest was analyzed by two-dimensional peptide mapping on a cellulose thin-layer sheet. After 94 h digestion, the autoradiograph of the peptide map showed a single 32P-labeled band with a molecular weight of approximately 1,200. These findings suggest that one specific serine residue of pig liver eIF-2 alpha was phosphorylated by the NEM-treated HCI.

Animals↗

PubMed1998

Identification and characterization of pancreatic eukaryotic initiation factor 2 alpha-subunit kinase, PEK, involved in translational control.

In response to various environmental stresses, eukaryotic cells down-regulate protein synthesis by phosphorylation of the alpha subunit of eukaryotic translation initiation factor 2 (eIF-2alpha). In mammals, the phosphorylation was shown to be carried out by eIF-2alpha kinases PKR and HRI. We report the identification and characterization of a cDNA from rat pancreatic islet cells that encodes a new related kinase, which we term pancreatic eIF-2alpha kinase, or PEK. In addition to a catalytic domain with sequence and structural features conserved among eIF-2alpha kinases, PEK contains a distinctive amino-terminal region 550 residues in length. Using recombinant PEK produced in Escherichia coli or Sf-9 insect cells, we demonstrate that PEK is autophosphorylated on both serine and threonine residues and that the recombinant enzyme can specifically phosphorylate eIF-2alpha on serine-51. Northern blot analyses indicate that PEK mRNA is expressed in all tissues examined, with highest levels in pancreas cells. Consistent with our mRNA assays, PEK activity was predominantly detected in pancreas and pancreatic islet cells. The regulatory role of PEK in protein synthesis was demonstrated both in vitro and in vivo. The addition of recombinant PEK to reticulocyte lysates caused a dose-dependent inhibition of translation. In the Saccharomyces model system, PEK functionally substituted for the endogenous yeast eIF-2alpha kinase, GCN2, by a process requiring the serine-51 phosphorylation site in eIF-2alpha. We also identified PEK homologs from both Caenorhabditis elegans and the puffer fish Fugu rubripes, suggesting that this eIF-2alpha kinase plays an important role in translational control from nematodes to mammals.

Amino Acid Sequence↗