PubMed Health⌕ Search

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 1,081 records · Page 60Linked to original sources

Developmental regulation of alkaline phosphatase in Dictyostelium discoideum.

The kinetics of accumulation of alkaline phosphatase activity were determined in cells of wild-type and morphologically aberrant mutant strains of Dictyostelium discoideum induced to develop synchronously on membrane supports. The enzyme specific activity increased slowly in wild-type cells until culmination when a dramatic rise in specific activity occurred. The patterns of accumulation in the mutant strains, as well as previous electrophoretic analysis, suggest that the two phases of accumulation may result from the synthesis of distinct isozymes. The rapid accumulation of alkaline phosphatase was found to require concomitant protein synthesis. Ribonucleic acid synthesis, on the other hand, could be inhibited during the 8 hr immediately preceding culmination without affecting the amount of enzyme accumulated. When ribonucleic acid synthesis was inhibited earlier in development, the accumulation of alkaline phosphatase was reduced. Comparison of these results with work on other developmentally controlled enzymes suggests that both transcriptional and translational control occurs during development of D. discoideum. The accumulation of alkaline phosphatase was shown to require specific cellular topography during culmination, suggesting that intercellular interactions which allow synthesis of alkaline phosphatase occur at that stage.

Alkaline Phosphatase↗

A Role for the SmpB-SsrA system in Yersinia pseudotuberculosis pathogenesis.

Yersinia utilizes a sophisticated type III secretion system to enhance its chances of survival and to overcome the host immune system. SmpB (small protein B) and SsrA (small stable RNA A) are components of a unique bacterial translational control system that help maintain the bacterial translational machinery in a fully operational state. We have found that loss of the SmpB-SsrA function causes acute defects in the ability of Yersinia pseudotuberculosis to survive in hostile environments. Most significantly, we show that mutations in smpB-ssrA genes render the bacterium avirulent and unable to cause mortality in mice. Consistent with these observations, we show that the mutant strain is unable to proliferate in macrophages and exhibits delayed Yop-mediated host cell cytotoxicity. Correspondingly, we demonstrate that the smpB-ssrA mutant suffers severe deficiencies in expression and secretion of Yersinia virulence effector proteins, and that this defect is at the level of transcription. Of further interest is the finding that the SmpB-SsrA system might play a similar role in the related type III secretion system that governs flagella assembly and bacterial motility. These findings highlight the significance of the SmpB-SsrA system in bacterial pathogenesis, survival under adverse environmental conditions, and motility.

Journal Article↗

Y-box binding protein 1: providing a new angle on translational regulation.

Current models of translational regulation are mostly focused on how translational factors engage a messenger mRNA to the ribosome to initiate translation. Since the majority of mRNAs in eukaryotes are translated in a cap-dependent manner, the mRNA 5' cap-binding protein eIF4E was characterized as a key player responsible for the recruitment of mRNAs to the initiation complex. The availability of eIF4E is believed to be especially critical for translational activation of mRNAs with extensive secondary structures in their 5'UTRs, many of which code for labile regulatory proteins essential for cell growth or viability. Surprisingly, little attention is paid to the other side of translational control, e.g., to define mechanisms responsible for translational silencing and storage of the above messages. In this review, we discuss the possibility that eIF4E per se may not be sufficient to release mRNAs from translational block. We found that many growth- and stress-related mRNAs are associated with the translational repressor YB-1, which can compete with the eIF4E-driven translation initiation complex for binding to the capped 5' mRNA terminus. Moreover, the cap-dependent repressor activity of YB-1 appears to be negatively regulated via Akt-mediated phosphorylation of the Ser-102 residue of YB-1. Taken together with recent evidence suggesting that translational activation of growth-related messages is a primary cellular response to activation of Ras-Erk and PI3K-Akt signaling pathways, our data suggest that differential expression of specific mRNA subsets is regulated by the PI3K-Akt pathway and achieved via coordinated activation of the components of translational machinery and inactivation of general translational repressors such as YB-1.

3T3 Cells↗

Proteomic identification of altered proteins in skeletal muscle during chronic potassium depletion: Implications for hypokalemic myopathy.

Prolonged potassium depletion is a well-known cause of myopathy. The pathophysiology of hypokalemic myopathy, however, remains unclear. We performed a gel-based, differential proteomics study to define altered proteins in skeletal muscles during chronic potassium depletion. BALB/c mice were fed with normal chow (0.36% K+) or K+-depleted (KD) diet (<0.001% K+) for 8 weeks (n = 5 in each group). Left gastrocnemius muscles were surgically removed from each animal. Histopathological examination showed mild-degree infiltration of polymornuclear and mononuclear cells at the interstitium of the KD muscles. Extracted proteins were resolved with two-dimensional electrophoresis (2-DE), and visualized with Coomassie Brilliant Blue R-250 stain. Quantitative intensity analysis revealed 16 up-regulated protein spots in the KD muscles, as compared to the controls. These differentially expressed proteins were subsequently identified by peptide mass fingerprinting and by quadrupole time-of-flight tandem mass spectrometry (Q-TOF MS/MS). Most of the altered proteins induced by chronic potassium depletion were muscle enzymes that play significant roles in several various metabolic pathways. Other up-regulated proteins included myosin-binding protein H, alpha-B Crystallin, and translationally controlled tumor protein (TCTP). These findings may lead to a new roadmap for research on hypokalemic myopathy, to better understanding of the pathophysiology of this medical disease, and to biomarker discovery.

Amino Acid Sequence↗

Biological models and genes of tumor reversion: cellular reprogramming through tpt1/TCTP and SIAH-1.

Tumor reversion is the process by which some cancer cells lose their malignant phenotype. This study was aimed at defining some of the molecular and phenotypic properties of this process. Biological models of tumor reversion were isolated from human leukemia and breast cancer cell lines by using the H-1 parvovirus as a selective agent. Differential gene expression analysis was performed between the parental malignant cells and their revertants or alternatively between these parental cells and their SIAH-1 transfectant counterparts. These SIAH-1 transfectants have a suppressed malignant phenotype and were used as a control for a viral-free system. Two hundred sixty-three genes were found to be either activated or inhibited during the reversion process, as confirmed by Northern blot analysis or quantitative PCR. Of these, 32% were differentially expressed in all systems, irrespective of whether parvovirus-selected, SIAH-1 overexpressing, or p53 mutant or wild-type cell lines were used, suggesting the existence of a universal mechanism underlying tumor reversion. Translationally Controlled Tumor Protein (tpt1/TCTP) has the strongest differential expression, down-regulated in the reversion of U937- and SIAH-1-overexpressing cells. Inhibition of TCTP expression by anti-sense cDNA or small interfering RNA molecules results in suppression of the malignant phenotype and in cellular reorganization, similar to the effect of SIAH-1. Hence, tumor reversion can be defined at the molecular level, not just as the reversal of malignant transformation, but as a biological process in its own right involving a cellular reprogramming mechanism, overriding genetic changes in cancer, by triggering an alternative pathway leading to suppression of tumorigenicity.

Basement Membrane↗

Molecular pharmacology and pharmacogenomics of artemisinin and its derivatives in cancer cells.

Secondary metabolites from plants can serve as defense against herbivores, microbes, viruses or competing plants. Many compounds from medicinal plants have pharmacological activities and thus may be a source for novel anti-tumor agents. We have analyzed natural products from traditional Chinese medicine during the past decade and focused our interest on the compound artemisinin from Artemisia annua L. (qinghao, sweet wormwood) and its derivatives. In addition to their anti-malarial properties, artemisinins are cytotoxic for cancer cells. The present review focuses on the mechanisms of action of artemisinins in cancer cells relating to: 1. anti-proliferative and anti-angiogenic effects, 2. induction of apoptosis, 3. oxidative stress, 4. oncogenes and tumor suppressor genes, and 5. multidrug resistance. Data on putative target molecules of artemisinins are presented and discussed, e.g. the translationally controlled tumor protein (TCTP). Emphasis is given to pharmacogenomic approaches to analyze the pleiotropic nature of mechanisms of artemisinins in cancer cells.

Angiogenesis Inhibitors↗

A comprehensive screen for chicken proteins that interact with proteins unique to virulent strains of Marek's disease virus.

Genetic resistance to Marek's disease (MD) has been proposed as a method to augment current vaccinal control of MD. Although it is possible to identify QTL and candidate genes that are associated with MD resistance, it is necessary to integrate functional screens with linkage analysis to confirm the identity of true MD resistance genes. To help achieve this objective, a comprehensive 2-hybrid screen was conducted using genes unique to virulent Marek's disease virus (MDV) strains. Potential MDV-host protein interactions were tested by an in vitro binding assay to confirm the initial two-hybrid results. As a result, 7 new MDV-chicken protein interactions were identified and included the chicken proteins MHC class II beta (BLB) and invariant (Ii) chain (CD74), growth-related translationally controlled tumor protein (TPT1), complement component Clq-binding protein (C1QBP), retinoblastoma-binding protein 4 (RBBP4), and alpha-enolase (ENO1). Mapping of the encoding chicken genes suggests that BLB, the gene for MHC class II beta chain, is a positional candidate gene. In addition, the known functions of the chicken proteins suggest mechanisms that MDV might use to evade the chicken immune system and alter host gene regulation. Taken together, our results indicate that integrated genomic methods provide a powerful strategy to gain insights on complex biological processes and yield a manageable number of genes and pathways for further characterization.

Animals↗

Acquisition of meiotic competence in growing mouse oocytes is controlled at both translational and posttranslational levels.

Full-grown mouse oocytes spontaneously resume meiosis in vitro when released from their follicular environment. By contrast, growing oocytes are not competent to resume meiosis; the molecular basis of meiotic competence is not known. Entry into M phase of the eukaryotic cell cycle is controlled by MPF, a catalytically active complex comprising p34cdc2 kinase and cyclin B. Incompetent oocytes contain levels of cyclin B comparable to those in competent oocytes, while their level of p34cdc2 is markedly lower; p34cdc2 accumulates abruptly at the end of oocyte growth, at the time of meiotic competence acquisition. We show here that this change in p34cdc2 concentration is not secondary to a corresponding change in the concentration of the cognate mRNA, indicating that translational control may be involved. Microinjection of translatable p34cdc2 mRNA into incompetent oocytes yielded high levels of the protein, but it did not lead to resumption of meiosis. Similarly, microinjection of cyclin B1 mRNA resulted in accumulation of the protein, but not in the acquisition of meiotic competence. By contrast, the microinjection of both p34cdc2 and cyclin B1 mRNAs in incompetent oocytes induced histone H1 and MAP kinase activation, germinal vesicle breakdown, and entry into M-phase including the translational activation of a dormant mRNA. Thus, endogenous cyclin B1 in incompetent oocytes is not available for interaction with p34cdc2, suggesting that a posttranslational event must occur to achieve meiotic competence. Microinjection of either p34cdc2 or cyclin B1 mRNAs accelerated meiotic reinitiation of okadaic acid-treated incompetent oocytes. Taken together, these results suggest that acquisition of meiotic competence by mouse oocytes is regulated at both translational and posttranslational levels.

Animals↗

Differential expression of Hsp90 isoforms in geldanamycin-treated 9L cells.

In mammals, two major Hsp90 isoforms (Hsp90alpha and Hsp90beta) have been identified and found to be highly conserved among different species. However, the expression control of Hsp90 isoforms at both transcriptional and translational levels is largely unknown. Herein, we quantitatively investigate the changes in the total mRNA and inductive protein levels of Hsp90alpha and Hsp90beta in rat gliosarcoma cells treated with geldanamycin (GA). The stability of mRNA and protein was estimated. The translational efficiency of Hsp90 isoforms was measured employing in vitro translation techniques. It was found that Hsp90alpha was more inducible than Hsp90beta after GA treatment, whereas the hsp90alpha mRNA level was lower than that of hsp90beta. In addition, higher translational efficiency of hsp90alpha mRNA was observed, suggesting that translational control played an important role. Taken together, our results indicate that differential expression between Hsp90alpha and Hsp90beta is a consequence of both distinct mRNA profiles and differential translation processes.

Animals↗

[The changes of gene expression in multiple myeloma treated with thalidomide].

OBJECTIVE: To investigate the effect of thalidomide on bone marrow cells gene expression in multiple myeloma (MM) patients with suppression subtractive hybridization (SSH) and explore the molecular mechanism of thalidomide therapy for MM. METHODS: In a MM patient receiving thalidomide therapy and bone marrow cell from himself, total RNA extraction, mRNA isolation and cDNA synthesis were carried out respectively with routine procedures. SSH were performed in A and B group respectively. The subtracted cDNA was selectively amplified by suppression PCR. The product was inserted into T vector, and then transfected into the competent host JM109. So two subtractive libraries were constructed. After blue-white screening, colonies were selected and plasmids extracted. Homologous comparation was conducted in GenBank. RESULTS: In group A, seven clones were isolated, including ribosomal protein L19 (HUMAN), IgG lambda chain v-v region (HUMAN), contains Alu repetitive element, NADH-ubiquinone oxidoreductase chain 2, elongation factor 1-gamma, human beta globin region, and 40S ribosomal protein S4 (HUMAN). In group B, six clones were isolated, including cytochrome B, up-regulated by 1,25-dihydroxyvitamin D(3) (VDUP1), NADH- ubiquinone oxidoreductase 20 Kd subunit, mu-calpain large subunit, tumor protein, translationally-controlled 1 (TPT1) and COATOMER alpha subunit. CONCLUSION: Thalidomide induces apoptosis and antiangiogenesis by down-regulating some genes and up-regulating some others genes.

Angiogenesis Inhibitors↗

Modelling molecular mechanisms controlling sequential gene expression in differentiating mammalian enterocytes.

The gut epithelium represents a continuous developmental system in which cell proliferation in intestinal crypts is followed by the sequential expression of digestive and absorptive functions as enterocytes migrate out of crypts to the tips of intestinal villi. We have developed a mathematical model in the present work to mimic these sequential aspects of enterocyte differentiation. Using this model allows the characteristics of lactase expression to be ascribed to transcriptional control. In the case of a glucose transporter, however, it became necessary to assume an additional translational control that decreased exponentially as enterocytes migrated along villi. The suggestion that this type of modelling is useful in predicting which set of enterocytes is likely to use translation or transcription to control gene expression is also discussed.

Animals↗

Identification of macrophage activation associated proteins by two-dimensional gel electrophoresis and microsequencing.

To understand activation in monocytes and macrophages we have studied changes in protein synthesis using the human monocytoid U937 cell line and two-dimensional polyacrylamide gel electrophoresis (2D PAGE) and protein sequencing. U937 cells that had been metabolically labeled during treatment with PMA, LPS, or IFN-gamma showed appreciable increases or decreases in synthesis of 14 proteins when analyzed by 2D PAGE. Although some 20 proteins are reported to be affected by these agents in U937 cells, none of them correspond with the 14 proteins studied here. Of the 14 observed changes, four spots (p41/65, p35/65, p26/44, p20/53) were up-regulated by PMA only, one (p16/44) by LPS only, five spots (p29/47, p26/45, p26/48, p12/47, p10/45) by both LPS and PMA, and, finally, one (p29/45) by all three agents. Two spots (p20/59 and p20/61) were down-regulated by IFN-gamma and one of these spots (p20/59) was up-regulated by LPS. Only one spot (p20/48) was up-regulated by IFN-gamma. Eleven spots with matching mobilities (both M(r) and pI) to those identified in U937 were observed on 2D PAGE gels from human culture derived macrophages. Ten spots from U937 were sequenced by Edman degradation. Two were could not identified from information contained in the available DNA and protein databases and thus represent novel proteins, whereas a further six of the proteins were N-terminally blocked. The remaining two (29/47 and 12/47, respectively) were identified from existing protein databases as translationally controlled tumor protein (TCTP) and cytokeratin. This is the first report of the presence of TCTP in hemopoietic cells and its modulation by PMA or LPS in any cell type. We believe that 2D PAGE and sequencing is a powerful approach for identifying key proteins in macrophage cellular activation.

Amino Acid Sequence↗

Effects of ELF magnetic fields on protein expression profile of human breast cancer cell MCF7.

Extremely Low Frequency Magnetic Fields (ELF MF) has been considered as a "possible human carcinogen" by International Agency for Research on Cancer (IARC) while credible mechanisms of its carcinogenicity remain unknown. In this study, a proteomics approach was employed to investigate the changes of protein expression profile induced by ELF MF in human breast cancer cell line MCF7, in order to determine ELF MF-responsive proteins. MCF7 cells were exposed to 50 Hz, 0.4 mT ELF MF for 24 h and the changes of protein profile were examined using two dimensional electrophoresis. Up to 6 spots have been statistically significantly altered (their expression levels were changed at least 5 fold up or down) compared with sham-exposed group. 19 ones were only detected in exposure group while 19 ones were missing. Three proteins were identified by LC-IT Tandem MS as RNA binding protein regulatory subunit, Proteasome subunit beta type 7 precursor and Translationally Controlled Tumor Protein. Our finding showed that 50 Hz, 0.4 mT ELF MF alternates the protein profile of MCF7 cell and may affect many physiological functions of normal cell and 2-DE coupled with MS is a promising approach to elucidating cellular effects of electromagnetic fields.

Biomarkers, Tumor↗

Exendin 4 controls insulin production in rat islet beta cells predominantly by potentiation of glucose-stimulated proinsulin biosynthesis at the translational level.

AIMS/HYPOTHESIS: Ideally, a therapeutic insulin secretagogue should coordinately increase insulin production and insulin secretion to maintain islet beta cell secretory capacity. We compared the incretin mimetic exendin 4 and the sulfonylurea glibenclamide (known as glyburide in the USA and Canada) for their effects in upholding a balance between (pro)insulin biosynthesis and insulin secretion in pancreatic islets. METHODS: Isolated rat islets were incubated for 1 or 16 h over a range of glucose concentrations (2.8-16.7 mmol/l) with or without exendin 4 (10 nmol/l) or glibenclamide (1 micromol/l). Islets were then analysed for preproinsulin mRNA expression by RNase protection and quantitative real-time RT-PCR assays. Proinsulin biosynthesis was analysed by metabolic pulse-radiolabelling, immunoprecipitation and PAGE. Insulin secretion and insulin content were analysed by radioimmunoassay. RESULTS: Neither exendin 4 nor glibenclamide affected islet preproinsulin mRNA expression. However, exendin 4 significantly increased glucose-induced proinsulin biosynthesis at the translational level within 1 h, in marked contrast to glibenclamide, which inhibited proinsulin biosynthesis, especially at basal and intermediate glucose concentrations. Exendin 4 potentiated insulin secretion in a glucose-dependent manner, whereas glibenclamide stimulated insulin secretion independently of glucose. Exendin 4 better maintained rat islet insulin content compared with glibenclamide, which depleted intracellular stores of insulin in islet beta cells by 40% within 16 h. CONCLUSIONS/INTERPRETATION: Exendin 4 maintains insulin stores and beta cell secretory capacity primarily by translational control of proinsulin biosynthesis in parallel to insulin secretion. Glibenclamide does not regulate insulin production in coordination with stimulated insulin secretion, and consequently depletes islet insulin stores, compromising secretory capacity. Thus, at the level of the beta cell, incretin mimetics have an advantage over sulfonylureas for treatment of type 2 diabetes.

Animals↗

Localization of eukaryotic initiation factor 2 in neuron primary cultures and established cell lines.

Eukaryotic initiation factor 2 (eIF-2) is a heterotrimeric protein with subunits alpha, beta and gamma that forms a ternary complex with Met-tRNA and GTP. It promotes the binding of Met-tRNA to ribosomes and controls translational rates via phosphorylation/dephosphorylation mechanisms. By means of immunofluorescence and post-embedding immunocytochemistry of intact cells and quantitative immunoblotting of cell extracts, the cellular distribution of the initiation factor has been examined in primary neuronal cultures as well as in two established cell lines: PC12 phaeochromocytoma cells and rat pituitary GH4C1 cells. Our results indicated that the initiation factor is located not only in the cytoplasm but also in the nuclei of the cultured neurons and cell lines. In the cytoplasm, immunocytochemical studies reveal that the factor is present mainly in those areas that are rich in ribosomes. In the nucleus, the immunolabelling of eukaryotic initiation factor 2 verified the presence of gold particles in both nucleolar and extranucleolar areas. The specific distribution of this factor on both sides of the nuclear envelope suggests that it might have some nuclear-related function(s) besides its already known role in the control of translation.

Animals↗

Mechanisms of artemisinin resistance in the rodent malaria pathogen Plasmodium yoelii.

Artemisinin and its derivatives are important new antimalarials which are now used widely in Southeast Asia. Clinically relevant artemisinin resistance has not yet been reported but is likely to occur. In order to understand how the malaria parasite might become resistant to this drug, we studied artemisinin resistance in the murine malaria parasite Plasmodium yoelii. The artemisinin-resistant strain (ART), which is approximately fourfold less sensitive to artemisinin than the sensitive NS strain, accumulated 43% less radiolabeled drug in vitro (P < 0.01). Within the parasite, the drug appeared to react with the same parasite proteins in both strains. The translationally controlled tumor protein, one of the artemisinin target proteins, did not differ between the strains. No DNA sequence difference was found, but the resistant strain was found to express 2.5-fold-more protein than the sensitive strain (P < 0.01). Thus, the phenotype of artemisinin resistance in P. yoelii appears to be multifactorial.

Amino Acid Sequence↗

Translational regulation of terminal oligopyrimidine mRNAs induced by serum and amino acids involves distinct signaling events.

Various mitogenic or growth inhibitory stimuli induce a rapid change in the association of terminal oligopyrimidine (TOP) mRNAs with polysomes. It is generally believed that such translational control hinges on the mammalian target of rapamycin (mTOR)-S6 kinase pathway. Amino acid availability affects the translation of TOP mRNAs, although the signaling pathway involved in this regulation is less well characterized. To investigate both serum- and amino acid-dependent control of TOP mRNA translation and the signaling pathways involved, HeLa cells were subjected to serum and/or amino acid deprivation and stimulation. Our results indicate the following. 1). Serum and amino acid deprivation had additive effects on TOP mRNA translation. 2). The serum content of the medium specifically affected TOP mRNA translation, whereas amino acid availability affected both TOP and non-TOP mRNAs. 3). Serum signaling to TOP mRNAs involved only a rapamycin-sensitive pathway, whereas amino acid signaling depended on both rapamycin-sensitive and rapamycin-insensitive but wortmannin-sensitive events. 4). Eukaryotic initiation factor-2alpha phosphorylation increased during amino acid deprivation, but not following serum deprivation. Interestingly, rapamycin treatment suggests a novel connection between the mTOR pathway and eukaryotic initiation factor-2alpha phosphorylation in mammalian cells, which may not, however, be involved in TOP mRNA translational regulation.

Amino Acids↗

Mechanistic perspectives for 1,2,4-trioxanes in anti-cancer therapy.

In addition to their well-known anti-malarial activity, artemisinin and its derivatives (1,2,4-trioxanes) possess potent activity against tumor cells in the nano- to micromolar range. Candidate genes that may contribute to the sensitivity and resistance of tumor cells to artemisinins were identified by pharmacogenomic and molecular pharmacological approaches. Target validation was performed using cell lines transfected with candidate genes or corresponding knockout cells. These genes are from classes with different biological function; for example, regulation of proliferation (BUB3, cyclins, CDC25A), angiogenesis (vascular endothelial growth factor and its receptor, matrix metalloproteinase-9, angiostatin, thrombospondin-1) or apoptosis (BCL-2, BAX). Artesunate triggers apoptosis both by p53-dependent and -independent pathways. Anti-oxidant stress genes (thioredoxin, catalase, gamma-glutamyl-cysteine synthetase, glutathione S-transferases) as well as the epidermal growth factor receptor confer resistance to artesunate. Cell lines over-expressing genes that confer resistance to established anti-tumor drugs (MDR1, MRP1, BCRP, dihydrofolate reductase, ribonucleotide reductase) were not cross-resistant to artesunate, indicating that this drug has a different target and is not subject to multidrug resistance. The Plasmodium translationally controlled tumor protein (TCTP) represents a known target protein of artemisinin and its derivatives in the malaria parasite. The microarray-based mRNA expression of human TCTP correlated with sensitivity to artesunate in tumor cells, suggesting that human TCTP contributes to response of tumor cells to the drug. The multi-factorial nature of cellular response to artemisinin and its derivatives may be beneficial to treat otherwise drug-resistant tumors and may explain why resistance development has not been observed in either cancer or malaria.

Animals↗