1351
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Sasikumar AN, Kinzy TG. Mutations in the chromodomain-like insertion of translation elongation factor 3 compromise protein synthesis through reduced ATPase activity. J Biol Chem 2013; 289:4853-60. [PMID: 24379402 DOI: 10.1074/jbc.m113.536201] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Translation elongation is mediated by ribosomes and multiple soluble factors, many of which are conserved across bacteria and eukaryotes. During elongation, eukaryotic elongation factor 1A (eEF1A; EF-Tu in bacteria) delivers aminoacylated-tRNA to the A-site of the ribosome, whereas eEF2 (EF-G in bacteria) translocates the ribosome along the mRNA. Fungal translation elongation is striking in its absolute requirement for a third factor, the ATPase eEF3. eEF3 binds close to the E-site of the ribosome and has been proposed to facilitate the removal of deacylated tRNA from the E-site. eEF3 has two ATP binding cassette (ABC) domains, the second of which carries a unique chromodomain-like insertion hypothesized to play a significant role in its binding to the ribosome. This model was tested in the current study using a mutational analysis of the Sac7d region of the chromodomain-like insertion. Specific mutations in this domain result in reduced growth rate as well as slower translation elongation. In vitro analysis demonstrates that these mutations do not affect the ability of eEF3 to interact with the ribosome. Kinetic analysis revealed a larger turnover number for ribosomes in comparison to eEF3, indicating that the partial reactions involving the ribosome are significantly faster than that of eEF3. Mutations in the chromodomain-like insertion severely compromise the ribosome stimulated ATPase of eEF3, strongly suggesting that it exerts an allosteric effect on the hydrolytic activity of eEF3. The chromodomain-like insertion is, therefore, vital to eEF3 function and may be targeted for developing novel antifungal drugs.
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Affiliation(s)
- Arjun N Sasikumar
- From the Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854-5635
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1352
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Carvalho KATD, Abdelwahid E, Ferreira RJ, Irioda AC, Guarita-Souza LC. Preclinical stem cell therapy in Chagas Disease: Perspectives for future research. World J Transplant 2013; 3:119-126. [PMID: 24392316 PMCID: PMC3879521 DOI: 10.5500/wjt.v3.i4.119] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/29/2013] [Accepted: 10/18/2013] [Indexed: 02/05/2023] Open
Abstract
Chagas cardiomyopathy still remains a challenging problem that is responsible for high morbidity and mortality in Central and Latin America. Chagas disease disrupts blood microcirculation via various autoimmune mechanisms, causing loss of cardiomyocytes and severe impairment of heart function. Different cell types and delivery approaches in Chagas Disease have been studied in both preclinical models and clinical trials. The main objective of this article is to clarify the reasons why the benefits that have been seen with cell therapy in preclinical models fail to translate to the clinical setting. This can be explained by crucial differences between the cellular types and pathophysiological mechanisms of the disease, as well as the differences between human patients and animal models. We discuss examples that demonstrate how the results from preclinical trials might have overestimated the efficacy of myocardial regeneration therapies. Future research should focus, not only on studying the best cell type to use but, very importantly, understanding the levels of safety and cellular interaction that can elicit efficient therapeutic effects in human tissue. Addressing the challenges associated with future research may ensure the success of stem cell therapy in improving preclinical models and the treatment of Chagas disease.
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1353
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Ouyang W, Torigoe C, Fang H, Xie T, Frucht DM. Anthrax lethal toxin inhibits translation of hypoxia-inducible factor 1α and causes decreased tolerance to hypoxic stress. J Biol Chem 2013; 289:4180-90. [PMID: 24366872 DOI: 10.1074/jbc.m113.530006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Hypoxia is considered to be a contributor to the pathology associated with administration of anthrax lethal toxin (LT). However, we report here that serum lactate levels in LT-treated mice are reduced, a finding inconsistent with the anaerobic metabolism expected to occur during hypoxia. Reduced lactate levels are also observed in the culture supernatants of LT-treated cells. LT inhibits the accumulation of hypoxia-inducible factor (HIF)-1α, a subunit of HIF-1, the master regulator directing cellular responses to hypoxia. The toxin has no effect on the transcription or protein turnover of HIF-1α, but instead it acts to inhibit HIF-1α translation. LT treatment diminishes phosphorylation of eIF4B, eIF4E, and rpS6, critical components of the intracellular machinery required for HIF-1α translation. Moreover, blockade of MKK1/2-ERK1/2, but not p38 or JNK signaling, lowers HIF-1α protein levels in both normoxic and hypoxic conditions, consistent with a role for MKK1 and MKK2 as the major targets of LT responsible for the inhibition of HIF-1α translation. The physiological importance of the LT-induced translation blockade is demonstrated by the finding that LT treatment decreases the survival of hepatocyte cell lines grown in hypoxic conditions, an effect that is overcome by preinduction of HIF-1α. Taken together, these data support a role for LT in dysregulating HIF-1α and thereby disrupting homeostatic responses to hypoxia, an environmental characteristic of certain tissues at baseline and/or during disseminated infection with Bacillus anthracis.
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Affiliation(s)
- Weiming Ouyang
- From the Division of Monoclonal Antibodies, Office of Biotechnology Products, Office of Pharmaceutical Science, Center for Drug Evaluation and Research, United States Food and Drug Administration, Bethesda, Maryland 20892
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1354
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Abstract
OBJECTIVE To address the problem of mapping local laboratory terminologies to Logical Observation Identifiers Names and Codes (LOINC). To study different ontology matching algorithms and investigate how the probability of term combinations in LOINC helps to increase match quality and reduce manual effort. MATERIALS AND METHODS We proposed two matching strategies: full name and multi-part. The multi-part approach also considers the occurrence probability of combined concept parts. It can further recommend possible combinations of concept parts to allow more local terms to be mapped. Three real-world laboratory databases from Taiwanese hospitals were used to validate the proposed strategies with respect to different quality measures and execution run time. A comparison with the commonly used tool, Regenstrief LOINC Mapping Assistant (RELMA) Lab Auto Mapper (LAM), was also carried out. RESULTS The new multi-part strategy yields the best match quality, with F-measure values between 89% and 96%. It can automatically match 70-85% of the laboratory terminologies to LOINC. The recommendation step can further propose mapping to (proposed) LOINC concepts for 9-20% of the local terminology concepts. On average, 91% of the local terminology concepts can be correctly mapped to existing or newly proposed LOINC concepts. CONCLUSIONS The mapping quality of the multi-part strategy is significantly better than that of LAM. It enables domain experts to perform LOINC matching with little manual work. The probability of term combinations proved to be a valuable strategy for increasing the quality of match results, providing recommendations for proposed LOINC conepts, and decreasing the run time for match processing.
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Affiliation(s)
- Li-Hui Lee
- Department of Computer Science, University of Leipzig, Leipzig, Germany Institute of Public Health, National Yang-Ming University, Taipei, Taiwan
| | - Anika Groß
- Department of Computer Science, University of Leipzig, Leipzig, Germany Interdisciplinary Center for Bioinformatics, University of Leipzig, Leipzig, Germany
| | - Michael Hartung
- Department of Computer Science, University of Leipzig, Leipzig, Germany Interdisciplinary Center for Bioinformatics, University of Leipzig, Leipzig, Germany
| | - Der-Ming Liou
- Institute of Biomedical Informatics, National Yang-Ming University, Taipei, Taiwan
| | - Erhard Rahm
- Department of Computer Science, University of Leipzig, Leipzig, Germany Interdisciplinary Center for Bioinformatics, University of Leipzig, Leipzig, Germany
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1355
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Cao J, He L, Lin G, Hu C, Dong R, Zhang J, Zhu H, Hu Y, Wagner CR, He Q, Yang B. Cap-dependent translation initiation factor, eIF4E, is the target for Ouabain-mediated inhibition of HIF-1α. Biochem Pharmacol 2013; 89:20-30. [PMID: 24345331 DOI: 10.1016/j.bcp.2013.12.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2013] [Revised: 12/05/2013] [Accepted: 12/05/2013] [Indexed: 12/29/2022]
Abstract
Hypoxia-inducible factor 1 (HIF-1), a heterodimeric transcription factor that mediates the adaptation of tumor cells and tissues to the hypoxic microenvironment, has attracted considerable interest as a potential therapeutic target. Recently, HIF-1α has been recognized as the critical target of cardiac glycosides for cancer therapy, but the molecular mechanism of cardiac glycosides' inhibition of HIF-1α is still poorly understood. In the present study, we observed that neither HIF-1α mRNA levels nor HIF-1α protein degradation are affected by Ouabain. However, Ouabain was found to be associated with the regulation of HIF-1α translation. Basing on in silico, in vitro and ex vivo models of translation processing, further studies revealed that eIF4E plays a critical role in the inhibitory effect of Ouabain on HIF-1α protein synthesis, rather than mTORC1, eIF2α signaling or Na(+)/K(+)-ATPase inhibition. Mechanistically, Ouabain directly binds eIF4E, disrupts eIF4E/eIF4G association (200 μM, Inhibit rate =61 ± 3%) but not the eIF4E/mRNA complex formation (200 μM, Inhibit rate =18 ± 5%) both in vitro and in cells, thereby inhibiting the intracellular cap-dependent translation. The association between Ouabain and eIF4E not only raises the hope of using cardiac glycosides for cancer therapeutics more rational, but also offers a pharmacologic means for developing novel anti-cancer HIF-1α antagonists.
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Affiliation(s)
- Ji Cao
- Department of Pharmacology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Lingjuan He
- Department of Pharmacology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Guanyu Lin
- Department of Pharmacology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Chunqi Hu
- ZJU-ENS Joint Laboratory of Medicinal Chemistry, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Rong Dong
- Department of Pharmacology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Jun Zhang
- Department of Pharmacology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Hong Zhu
- Department of Pharmacology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Yongzhou Hu
- ZJU-ENS Joint Laboratory of Medicinal Chemistry, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Carston R Wagner
- Department of Chemistry, University of Minnesota, Minneapolis, MN, USA
| | - Qiaojun He
- Department of Pharmacology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China
| | - Bo Yang
- Department of Pharmacology, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.
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1356
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Abstract
The human tRNAome consists of more than 500 interspersed tRNA genes comprising 51 anticodon families of largely unequal copy number. We examined tRNA gene copy number variation (tgCNV) in six individuals; two kindreds of two parents and a child, using high coverage whole genome sequence data. Such differences may be important because translation of some mRNAs is sensitive to the relative amounts of tRNAs and because tRNA competition determines translational efficiency vs. fidelity and production of native vs. misfolded proteins. We identified several tRNA gene clusters with CNV, which in some cases were part of larger iterations. In addition there was an isolated tRNALysCUU gene that was absent as a homozygous deletion in one of the parents. When assessed by semiquantitative PCR in 98 DNA samples representing a wide variety of ethnicities, this allele was found deleted in hetero- or homozygosity in all groups at ~50% frequency. This is the first report of copy number variation of human tRNA genes. We conclude that tgCNV exists at significant levels among individual humans and discuss the results in terms of genetic diversity and prior genome wide association studies (GWAS) that suggest the importance of the ratio of tRNALys isoacceptors in Type-2 diabetes.
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Affiliation(s)
- James R Iben
- Intramural Research Program on Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Richard J Maraia
- Intramural Research Program on Genomics of Differentiation, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
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1357
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Goode AD, Eakin EG. Dissemination of an evidence-based telephone-delivered lifestyle intervention: factors associated with successful implementation and evaluation. Transl Behav Med 2013; 3:351-6. [PMID: 24294323 DOI: 10.1007/s13142-013-0219-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
To inform wider-scale dissemination efforts of health behavior change interventions, we need to better understand factors associated with successful implementation and evaluation in nonresearch settings. Using the experience of the Optimal Health Program dissemination (OHP), a 12-month evidence-based telephone-delivered intervention for physical activity, healthy eating, and weight loss, we provide a detailed account according to the reach, efficacy/effectiveness, adoption, implementation, and maintenance (RE-AIM) framework of the supports that were needed to facilitate the delivery and evaluation of the program in an applied community-based primary health care setting. Substantial initial research support including development of data collection procedures, staff training in intervention protocols, and ongoing support for fidelity of data collection and intervention delivery, as well as evaluation and reporting of outcomes was required. The RE-AIM framework can highlight common elements that will require attention from researchers to promote success of programs in applied settings.
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Affiliation(s)
- Ana D Goode
- School of Population Health, Cancer Prevention Research Centre, The University of Queensland, Herston Rd, Herston, Queensland 4006 Australia
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1358
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Jones DL, Lopez M, Simons H, Diaz-Gloster M, Tobin JN, Weiss SM. Translation of a comprehensive health behavior intervention for women living with HIV: the SMART/EST Women's Program. Transl Behav Med 2013; 3:416-25. [PMID: 24294330 PMCID: PMC3830012 DOI: 10.1007/s13142-013-0213-4] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
Translation of behavioral interventions into community settings for people living with HIV/AIDS can decrease the risk of comorbid conditions. This study was designed to determine whether a multiple health behavior intervention for women with HIV/AIDS could be effectively translated into community health centers (CHCs), delivered by CHC primary care staff. Health Resources and Services Administration-supported CHCs in Miami, FL, and the New York metropolitan area participated. Six health behavior domains were assessed at baseline, 6 months, and 12 months post-intervention: nutrition, physical activity, sexual risk behavior, alcohol use, drug use, and tobacco use. Behavioral outcomes were compared between research staff-led and CHC staff-led intervention groups. Research staff and CHC staff outcomes were similar for the majority of outcomes. Results indicate that complex, multicomponent behavioral interventions can be translated into community-based settings with existing CHC staff and can produce clinical effects similar to those achieved by research staff.
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Affiliation(s)
- Deborah L Jones
- />Department of Psychiatry & Behavioral Sciences, Miller School of Medicine, University of Miami, 1400 NW 10th Ave., Miami, FL 33136 USA
| | - Maria Lopez
- />Department of Psychiatry & Behavioral Sciences, Miller School of Medicine, University of Miami, 1400 NW 10th Ave., Miami, FL 33136 USA
| | | | | | - Jonathan N Tobin
- />Clinical Directors Network, New York, NY USA
- />Center for Clinical and Translational Science, The Rockefeller University, New York, NY USA
| | - Stephen M Weiss
- />Department of Psychiatry & Behavioral Sciences, Miller School of Medicine, University of Miami, 1400 NW 10th Ave., Miami, FL 33136 USA
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1359
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Govindaraju S, Lee BS. Adaptive and maladaptive expression of the mRNA regulatory protein HuR. World J Biol Chem 2013; 4:111-118. [PMID: 24340134 PMCID: PMC3856306 DOI: 10.4331/wjbc.v4.i4.111] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Revised: 08/31/2013] [Accepted: 11/05/2013] [Indexed: 02/05/2023] Open
Abstract
The RNA-binding proteins involved in regulation of mRNA post-transcriptional processing and translation control the fates of thousands of mRNA transcripts and basic cellular processes. The best studied of these, HuR, is well characterized as a mediator of mRNA stability and translation, and more recently, as a factor in nuclear functions such as pre-mRNA splicing. Due to HuR’s role in regulating thousands of mRNA transcripts, including those for other RNA-binding proteins, HuR can act as a master regulator of cell survival and proliferation. HuR itself is subject to multiple post-translational modifications including regulation of its nucleocytoplasmic distribution. However, the mechanisms that govern HuR levels in the cell have only recently begun to be defined. These mechanisms are critical to cell health, as it has become clear in recent years that aberrant expression of HuR can lead alternately to decreased cell viability or to promotion of pathological proliferation and invasiveness. HuR is expressed as alternate mRNAs that vary in their untranslated regions, leading to differences in transcript stability and translatability. Multiple transcription factors and modulators of mRNA stability that regulate HuR mRNA expression have been identified. In addition, translation of HuR is regulated by numerous microRNAs, several of which have been demonstrated to have anti-tumor properties due to their suppression of HuR expression. This review summarizes the current state of knowledge of the factors that regulate HuR expression, along with the circumstances under which these factors contribute to cancer and inflammation.
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1360
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Esnault S, Kelly EA, Johansson MW, Liu LY, Han ST, Akhtar M, Sandbo N, Mosher DF, Denlinger LC, Mathur SK, Malter JS, Jarjour NN. Semaphorin 7A is expressed on airway eosinophils and upregulated by IL-5 family cytokines. Clin Immunol 2014; 150:90-100. [PMID: 24333536 DOI: 10.1016/j.clim.2013.11.009] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2013] [Accepted: 11/13/2013] [Indexed: 11/20/2022]
Abstract
Semaphorin 7A (sema7a) plays a major role in TGF-β1-induced lung fibrosis. Based on the accumulating evidence that eosinophils contribute to fibrosis/remodeling in the airway, we hypothesized that airway eosinophils may be a significant source of sema7a. In vivo, sema7a was expressed on the surface of circulating eosinophils and upregulated on bronchoalveolar lavage eosinophils obtained after segmental bronchoprovocation with allergen. Based on mRNA levels in unfractionated and isolated bronchoalveolar cells, eosinophils are the predominant source of sema7a. In vitro, among the members of the IL-5-family cytokines, sema7a protein on the surface of blood eosinophils was increased more by IL-3 than by GM-CSF or IL-5. Cytokine-induced expression of cell surface sema7a required translation of newly synthesized protein. Finally, a recombinant sema7a induced alpha-smooth muscle actin production in human bronchial fibroblasts. semaphorin 7A is a potentially important modulator of eosinophil profibrotic functions in the airway remodeling of patients with chronic asthma.
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1361
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Abstract
Hox genes encode a family of transcriptional regulators that elicit distinct developmental programmes along the head-to-tail axis of animals. The specific regional functions of individual Hox genes largely reflect their restricted expression patterns, the disruption of which can lead to developmental defects and disease. Here, we examine the spectrum of molecular mechanisms controlling Hox gene expression in model vertebrates and invertebrates and find that a diverse range of mechanisms, including nuclear dynamics, RNA processing, microRNA and translational regulation, all concur to control Hox gene outputs. We propose that this complex multi-tiered regulation might contribute to the robustness of Hox expression during development.
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Affiliation(s)
- Moisés Mallo
- Instituto Gulbenkian de Ciência, Rua da Quinta Grande 6, 2780-156 Oeiras, Portugal
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1362
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Lyle AN, Remus EW, Fan AE, Lassègue B, Walter GA, Kiyosue A, Griendling KK, Taylor WR. Hydrogen peroxide regulates osteopontin expression through activation of transcriptional and translational pathways. J Biol Chem 2013; 289:275-85. [PMID: 24247243 DOI: 10.1074/jbc.m113.489641] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Recent in vivo studies establish that osteopontin (OPN) expression is hydrogen peroxide (H2O2)-dependent. However, the mechanisms by which H2O2 increases OPN expression remain poorly defined. OPN protein expression increased in an unusual biphasic pattern in response to H2O2. To investigate whether these increases were mediated through transcriptional and/or translational regulation of OPN, smooth muscle cells stimulated with 50 μM H2O2 were used as an in vitro cell system. Early protein increases at 6 h were not preceded by increased mRNA, whereas later increases (18 h) were, suggesting multiple mechanisms of regulation by H2O2. Polyribosomal fractionation assays established that early increases (6 h) in OPN expression were due to increased translation. This increase in translation occurred through phosphorylation of 4E-BP1 at the reactive oxygen species-sensitive Ser-65, which allowed for release and activation of eukaryotic initiation factor eIF4E and subsequent OPN translation. This early increase (6 h) in OPN was blunted in cells expressing a phospho-deficient 4E-BP1 mutant. H2O2 stimulation increased rat OPN promoter activity at 8 and 18 h, and promoter truncation studies established that promoter region -2284 to -795 is crucial for H2O2-dependent OPN transcription. ChIP studies determined that H2O2-dependent transcription is mediated by the reactive oxygen species-sensitive transcription factors NF-κB and AP-1. In conclusion, H2O2 stimulates OPN expression in a unique biphasic pattern, where early increases are translational and late increases are transcriptional.
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1363
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Filisetti D, Théobald-Dietrich A, Mahmoudi N, Rudinger-Thirion J, Candolfi E, Frugier M. Aminoacylation of Plasmodium falciparum tRNA(Asn) and insights in the synthesis of asparagine repeats. J Biol Chem 2013; 288:36361-71. [PMID: 24196969 DOI: 10.1074/jbc.m113.522896] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Genome sequencing revealed an extreme AT-rich genome and a profusion of asparagine repeats associated with low complexity regions (LCRs) in proteins of the malarial parasite Plasmodium falciparum. Despite their abundance, the function of these LCRs remains unclear. Because they occur in almost all families of plasmodial proteins, the occurrence of LCRs cannot be associated with any specific metabolic pathway; yet their accumulation must have given selective advantages to the parasite. Translation of these asparagine-rich LCRs demands extraordinarily high amounts of asparaginylated tRNA(Asn). However, unlike other organisms, Plasmodium codon bias is not correlated to tRNA gene copy number. Here, we studied tRNA(Asn) accumulation as well as the catalytic capacities of the asparaginyl-tRNA synthetase of the parasite in vitro. We observed that asparaginylation in this parasite can be considered standard, which is expected to limit the availability of asparaginylated tRNA(Asn) in the cell and, in turn, slow down the ribosomal translation rate when decoding asparagine repeats. This observation strengthens our earlier hypothesis considering that asparagine rich sequences act as "tRNA sponges" and help cotranslational folding of parasite proteins. However, it also raises many questions about the mechanistic aspects of the synthesis of asparagine repeats and about their implications in the global control of protein expression throughout Plasmodium life cycle.
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Affiliation(s)
- Denis Filisetti
- From the Architecture et Réactivité de l'ARN, Université de Strasbourg, CNRS, Institut de Biologie Moléculaire et Cellulaire, 15 rue René Descartes, 67084 Strasbourg cedex, France and
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1364
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Shibata N, Carlin AF, Spann NJ, Saijo K, Morello CS, McDonald JG, Romanoski CE, Maurya MR, Kaikkonen MU, Lam MT, Crotti A, Reichart D, Fox JN, Quehenberger O, Raetz CRH, Sullards MC, Murphy RC, Merrill AH, Brown HA, Dennis EA, Fahy E, Subramaniam S, Cavener DR, Spector DH, Russell DW, Glass CK. 25-Hydroxycholesterol activates the integrated stress response to reprogram transcription and translation in macrophages. J Biol Chem 2013; 288:35812-23. [PMID: 24189069 DOI: 10.1074/jbc.m113.519637] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
25-Hydroxycholesterol (25OHC) is an enzymatically derived oxidation product of cholesterol that modulates lipid metabolism and immunity. 25OHC is synthesized in response to interferons and exerts broad antiviral activity by as yet poorly characterized mechanisms. To gain further insights into the basis for antiviral activity, we evaluated time-dependent responses of the macrophage lipidome and transcriptome to 25OHC treatment. In addition to altering specific aspects of cholesterol and sphingolipid metabolism, we found that 25OHC activates integrated stress response (ISR) genes and reprograms protein translation. Effects of 25OHC on ISR gene expression were independent of liver X receptors and sterol-response element-binding proteins and instead primarily resulted from activation of the GCN2/eIF2α/ATF4 branch of the ISR pathway. These studies reveal that 25OHC activates the integrated stress response, which may contribute to its antiviral activity.
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1365
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Abstract
The mammalian genome is replete with various classes of non-coding (nc) RNA genes. Many of them actively transcribe, and their relevance to CNS diseases is just beginning to be understood. CNS is one of the organs in the body that shows very high ncRNAs activity. Recent studies demonstrated that cerebral ischemia rapidly changes the expression profiles of different classes of ncRNAs: including microRNA, long noncoding RNA and piwi-interacting RNA. Several studies further showed that post-ischemic neuronal death and/or plasticity/regeneration can be altered by modulating specific microRNAs. These studies are of interest for therapeutic development as they may contribute to identifying new ncRNA targets that can be modulated to prevent secondary brain damage after stroke.
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Affiliation(s)
- Raghu Vemuganti
- Department of Neurological Surgery, University of Wisconsin, Madison, WI, USA.
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1366
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Matsuo T, Noguchi Y, Shindo M, Morita Y, Oda Y, Yoshida E, Hamada H, Harada M, Shiokawa Y, Nishida T, Tominaga R, Kikushige Y, Akashi K, Kudoh J, Shimizu N, Tanaka Y, Umemura T, Taniguchi T, Yoshimura A, Kobayashi T, Mitsuyama M, Kurisaki H, Katsuta H, Nagafuchi S. Regulation of human autoimmune regulator (AIRE) gene translation by miR-220b. Gene 2013; 530:19-25. [PMID: 23954874 DOI: 10.1016/j.gene.2013.08.015] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Revised: 08/04/2013] [Accepted: 08/05/2013] [Indexed: 11/23/2022]
Abstract
Although mutations of autoimmune regulator (AIRE) gene are responsible for autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED), presenting a wide spectrum of many characteristic and non-characteristic clinical features, some patients lack AIRE gene mutations. Therefore, something other than a mutation, such as dysregulation of AIRE gene, may be a causal factor for APECED or its related diseases. However, regulatory mechanisms for AIRE gene expression and/or translation have still remained elusive. We found that IL-2-stimulated CD4(+) T (IL-2T) cells showed a high expression of AIRE gene, but very low AIRE protein production, while Epstein-Barr virus-transformed B (EBV-B) cells express both AIRE gene and AIRE protein. By using microarray analysis, we could identify miR-220b as a possible regulatory mechanism for AIRE gene translation in IL-2T cells. Here we report that miR-220b significantly reduced the expression of AIRE protein in AIRE gene with 3'UTR region transfected 293T cells, whereas no alteration of AIRE protein production was observed in the open reading frame of AIRE gene alone transfected cells. In addition, anti-miR-220b reversed the inhibitory function of miR-220b for the expression of AIRE protein in AIRE gene with 3'UTR region transfected cells. Moreover, when AIRE gene transfected cells with mutated 3'UTR were transfected with miR-220b, no reduction of AIRE protein production was observed. Taken together, it was concluded that miR-220b inhibited the AIRE gene translation through the 3'UTR region of AIRE gene, indicating that miR-220b could serve as a regulator for human AIRE gene translation.
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Affiliation(s)
- Tomohito Matsuo
- Department of Medical Science and Technology, Graduate School of Medical Sciences, Kyushu University, Fukuoka 812-8582, Japan
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1367
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Carroll K, Hastings C, Miller CL. Amino acids 78 and 79 of Mammalian Orthoreovirus protein µNS are necessary for stress granule localization, core protein λ2 interaction, and de novo virus replication. Virology 2013; 448:133-45. [PMID: 24314644 DOI: 10.1016/j.virol.2013.10.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2013] [Revised: 08/01/2013] [Accepted: 10/05/2013] [Indexed: 12/25/2022]
Abstract
At early times in Mammalian Orthoreovirus (MRV) infection, cytoplasmic inclusions termed stress granules (SGs) are formed as a component of the innate immune response, however, at later times they are no longer present despite continued immune signaling. To investigate the roles of MRV proteins in SG modulation we examined non-structural protein µNS localization relative to SGs in infected and transfected cells. Using a series of mutant plasmids, we mapped the necessary μNS residues for SG localization to amino acids 78 and 79. We examined the capacity of a μNS(78-79) mutant to associate with known viral protein binding partners of μNS and found that it loses association with viral core protein λ2. Finally, we show that while this mutant cannot support de novo viral replication, it is able to rescue replication following siRNA knockdown of μNS. These data suggest that μNS association with SGs, λ2, or both play roles in MRV replication.
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Affiliation(s)
- Kate Carroll
- Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames 50011, IA, USA; Program in Genetics, Iowa State University, Ames 50011, IA, USA
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1368
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Nasrallah FA, Tay HC, Chuang KH. Detection of functional connectivity in the resting mouse brain. Neuroimage 2013; 86:417-24. [PMID: 24157920 DOI: 10.1016/j.neuroimage.2013.10.025] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Revised: 10/08/2013] [Accepted: 10/10/2013] [Indexed: 11/25/2022] Open
Abstract
Resting-state functional connectivity, manifested as spontaneous synchronous activity in the brain, has been detected by functional MRI (fMRI) across species such as humans, monkeys, and rats. Yet, most networks, especially the classical bilateral connectivity between hemispheres, have not been reliably found in the mouse brain. This could be due to anesthetic effects on neural activity and difficulty in maintaining proper physiology and neurovascular coupling in anesthetized mouse. For example, α2 adrenoceptor agonist, medetomidine, is a sedative for longitudinal mouse fMRI. However, the higher dosage needed compared to rats may suppress the functional synchrony and lead to unilateral connectivity. In this study, we investigated the influence of medetomidine dosage on neural activation and resting-state networks in mouse brain. We show that mouse can be stabilized with dosage as low as 0.1mg/kg/h. The stimulation-induced somatosensory activation was unchanged when medetomidine was increased from 0.1 to 6 and 10 folds. Especially, robust bilateral connectivity can be observed in the primary, secondary somatosensory and visual cortices, as well as the hippocampus, caudate putamen, and thalamus at low dose of medetomidine. Significant suppression of inter-hemispheric correlation was seen in the thalamus, where the receptor density is high, under 0.6mg/kg/h, and in all regions except the caudate, where the receptor density is low, under 1.0mg/kg/h. Furthermore, in mice whose activation was weaker or took longer time to detect, the bilateral connectivity was lower. This demonstrates that, with proper sedation and conservation of neurovascular coupling, similar bilateral networks like other species can be detected in the mouse brain.
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Affiliation(s)
- Fatima A Nasrallah
- Magnetic Resonance Imaging Group, Singapore Bioimaging Consortium, Agency for Science Technology and Research, Singapore
| | - Hui-Chien Tay
- Magnetic Resonance Imaging Group, Singapore Bioimaging Consortium, Agency for Science Technology and Research, Singapore
| | - Kai-Hsiang Chuang
- Magnetic Resonance Imaging Group, Singapore Bioimaging Consortium, Agency for Science Technology and Research, Singapore; Clinical Imaging Research Centre, National University of Singapore, Singapore; Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
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1369
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Rosenblum G, Cooperman BS. Engine out of the chassis: cell-free protein synthesis and its uses. FEBS Lett 2013; 588:261-8. [PMID: 24161673 DOI: 10.1016/j.febslet.2013.10.016] [Citation(s) in RCA: 74] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 10/14/2013] [Accepted: 10/15/2013] [Indexed: 12/15/2022]
Abstract
The translation machinery is the engine of life. Extracting the cytoplasmic milieu from a cell affords a lysate capable of producing proteins in concentrations reaching to tens of micromolar. Such lysates, derivable from a variety of cells, allow the facile addition and subtraction of components that are directly or indirectly related to the translation machinery and/or the over-expressed protein. The flexible nature of such cell-free expression systems, when coupled with high throughput monitoring, can be especially suitable for protein engineering studies, allowing one to bypass multiple steps typically required using conventional in vivo protein expression.
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Affiliation(s)
- Gabriel Rosenblum
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, United States.
| | - Barry S Cooperman
- Department of Chemistry, University of Pennsylvania, Philadelphia, PA 19104-6323, United States
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1370
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Schwenzer H, Scheper GC, Zorn N, Moulinier L, Gaudry A, Leize E, Martin F, Florentz C, Poch O, Sissler M. Released selective pressure on a structural domain gives new insights on the functional relaxation of mitochondrial aspartyl-tRNA synthetase. Biochimie 2013; 100:18-26. [PMID: 24120687 DOI: 10.1016/j.biochi.2013.09.027] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Accepted: 09/30/2013] [Indexed: 10/26/2022]
Abstract
Mammalian mitochondrial aminoacyl-tRNA synthetases are nuclear-encoded enzymes that are essential for mitochondrial protein synthesis. Due to an endosymbiotic origin of the mitochondria, many of them share structural domains with homologous bacterial enzymes of same specificity. This is also the case for human mitochondrial aspartyl-tRNA synthetase (AspRS) that shares the so-called bacterial insertion domain with bacterial homologs. The function of this domain in the mitochondrial proteins is unclear. Here, we show by bioinformatic analyses that the sequences coding for the bacterial insertion domain are less conserved in opisthokont and protist than in bacteria and viridiplantae. The divergence suggests a loss of evolutionary pressure on this domain for non-plant mitochondrial AspRSs. This discovery is further connected with the herein described occurrence of alternatively spliced transcripts of the mRNAs coding for some mammalian mitochondrial AspRSs. Interestingly, the spliced transcripts alternately lack one of the four exons that code for the bacterial insertion domain. Although we showed that the human alternative transcript is present in all tested tissues; co-exists with the full-length form, possesses 5'- and 3'-UTRs, a poly-A tail and is bound to polysomes, we were unable to detect the corresponding protein. The relaxed selective pressure combined with the occurrence of alternative splicing, involving a single structural sub-domain, favors the hypothesis of the loss of function of this domain for AspRSs of mitochondrial location. This evolutionary divergence is in line with other characteristics, established for the human mt-AspRS, that indicate a functional relaxation of non-viridiplantae mt-AspRSs when compared to bacterial and plant ones, despite their common ancestry.
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Affiliation(s)
- Hagen Schwenzer
- Architecture et Réactivité de l'ARN, CNRS, Université de Strasbourg, IBMC - 15 rue René Descartes, F-67084 Strasbourg Cedex, France
| | - Gert C Scheper
- Department of Pediatrics and Child Neurology, VU University Medical Center, 1081 HV Amsterdam, The Netherlands
| | - Nathalie Zorn
- Laboratoire de Spectrométrie de Masse des Interactions et des Systèmes, Chimie de la Matière Complexe, 1 rue Blaise Pascal, F-67008 Strasbourg Cedex, France
| | - Luc Moulinier
- Laboratoire de Bioinformatique et de Génomique Intégratives, IGBMC, 1 rue Laurent Fries BP-10142, F-67404 Illkirch Cedex, France
| | - Agnès Gaudry
- Architecture et Réactivité de l'ARN, CNRS, Université de Strasbourg, IBMC - 15 rue René Descartes, F-67084 Strasbourg Cedex, France
| | - Emmanuelle Leize
- Laboratoire de Spectrométrie de Masse des Interactions et des Systèmes, Chimie de la Matière Complexe, 1 rue Blaise Pascal, F-67008 Strasbourg Cedex, France
| | - Franck Martin
- Architecture et Réactivité de l'ARN, CNRS, Université de Strasbourg, IBMC - 15 rue René Descartes, F-67084 Strasbourg Cedex, France
| | - Catherine Florentz
- Architecture et Réactivité de l'ARN, CNRS, Université de Strasbourg, IBMC - 15 rue René Descartes, F-67084 Strasbourg Cedex, France
| | - Olivier Poch
- Laboratoire de Bioinformatique et de Génomique Intégratives, IGBMC, 1 rue Laurent Fries BP-10142, F-67404 Illkirch Cedex, France
| | - Marie Sissler
- Architecture et Réactivité de l'ARN, CNRS, Université de Strasbourg, IBMC - 15 rue René Descartes, F-67084 Strasbourg Cedex, France.
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1371
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Villa N, Do A, Hershey JWB, Fraser CS. Human eukaryotic initiation factor 4G (eIF4G) protein binds to eIF3c, -d, and -e to promote mRNA recruitment to the ribosome. J Biol Chem 2013; 288:32932-40. [PMID: 24092755 DOI: 10.1074/jbc.m113.517011] [Citation(s) in RCA: 111] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Recruitment of mRNA to the 40S ribosomal subunit requires the coordinated interaction of a large number of translation initiation factors. In mammals, the direct interaction between eukaryotic initiation factor 4G (eIF4G) and eIF3 is thought to act as the molecular bridge between the mRNA cap-binding complex and the 40S subunit. A discrete ∼90 amino acid domain in eIF4G is responsible for binding to eIF3, but the identity of the eIF3 subunit(s) involved is less clear. The eIF3e subunit has been shown to directly bind eIF4G, but the potential role of other eIF3 subunits in stabilizing this interaction has not been investigated. It is also not clear if the eIF4A helicase plays a role in stabilizing the interaction between eIF4G and eIF3. Here, we have used a fluorescence anisotropy assay to demonstrate that eIF4G binds to eIF3 independently of eIF4A binding to the middle region of eIF4G. By using a site-specific cross-linking approach, we unexpectedly show that the eIF4G-binding surface in eIF3 is comprised of the -c, -d and -e subunits. Screening multiple cross-linker positions reveals that eIF4G contains two distinct eIF3-binding subdomains within the previously identified eIF3-binding domain. Finally, by employing an eIF4G-dependent translation assay, we establish that both of these subdomains are required for efficient mRNA recruitment to the ribosome and stimulate translation. Our study reveals unexpected complexity to the eIF3-eIF4G interaction that provides new insight into the regulation of mRNA recruitment to the human ribosome.
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Affiliation(s)
- Nancy Villa
- From the Department of Molecular and Cell Biology, College of Biological Sciences, and
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1372
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Whiteley JA, Williams DM, Jennings EG, Ciccolo JT, Bock BC, Dunsiger S, Marcus BH. The challenges of translating an efficacious smoking cessation program, Commit to Quit, to the community setting of YMCAs. Transl Behav Med 2013; 3:47-58. [PMID: 24073160 DOI: 10.1007/s13142-012-0181-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Commit to Quit (CTQ), a program that utilized vigorous intensity exercise as an adjunct to a cognitive-behavioral smoking cessation program, was shown to be effective for female smokers (Marcus et al., Prev Med 26(4):586-597, 1997; Marcus et al., Arch Intern Med 159(11):1229-1234, 1999). Adapting effective programs, such as CTQ, to community settings could lead to a large public health impact as the program could substantially increase its reach. This case study chronicles the steps taken by researchers to translate CTQ from the medical to the community setting of YMCAs (CTQY). Use of aspects of Diffusion Theory [3] such as identifying a champion of the program and attending to the characteristics of an innovation to enhance program adoption are discussed. Details regarding attending to the tensions between internal and external validity as the program was adapted to the community setting are also outlined. The challenges of conducting community trials are discussed.
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1373
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Abstract
The Division of HIV/AIDS Prevention at the National Center for HIV, Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention seeks to make evidence-based behavioral HIV prevention interventions (EBIs) accessible to HIV prevention providers through a systematic process of identification, packaging, and dissemination. This update synthesizes that process and describes recent efforts to expand the use of EBIs internationally through partnerships between the CDC's Global AIDS Program, academic research centers, and other international and US agencies.
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1374
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Elliot DL, Mackinnon DP, Mabry L, Kisbu-Sakarya Y, Defrancesco CA, Coxe SJ, Kuehl KS, Moe EL, Goldberg L, Favorite KC. Worksite wellness program implementation: a model of translational effectiveness. Transl Behav Med 2012; 2:228-35. [PMID: 24073114 DOI: 10.1007/s13142-012-0121-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
Abstract
Occupational health promotion programs with documented efficacy have not penetrated worksites. Establishing an implementation model would allow focusing on mediating aspects to enhance installation and use of evidence-based occupational wellness interventions. The purpose of the study was to implement an established wellness program in fire departments and define predictors of program exposure/dose to outcomes to define a cross-sectional model of translational effectiveness. The study is a prospective observational study among 12 NW fire departments. Data were collected before and following installation, and findings were used to conduct mediation analysis and develop a translational effectiveness model. Worker age was examined for its impact. Leadership, scheduling/competing demands, and tailoring were confirmed as model components, while organizational climate was not a factor. The established model fit data well (χ (2)(9) = 25.57, CFI = 0.99, RMSEA = 0.05, SRMR = 0.03). Older firefighters, nearing retirement, appeared to have influences that both enhanced and hindered participation. Findings can inform implementation of worksite wellness in fire departments, and the prioritized influences and translational model can be validated and manipulated in these and other settings to more efficiently move health promotion science to service.
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1375
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Jones JB, Bruce CA, Shah NR, Taylor WF, Stewart WF. Shared decision making: using health information technology to integrate patient choice into primary care. Transl Behav Med 2013; 1:123-33. [PMID: 24073039 DOI: 10.1007/s13142-011-0023-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Advances in shared decision making (SDM) have not successfully translated to practice. We describe our experience and lessons learned in translating an SDM process for primary care cardiovascular disease management. The SDM process operationalized recognized SDM elements using workflow modifications, a computerized patient questionnaire, an automated risk calculator to identify at-risk patients, a web-based tool for patients to choose interventions, automated feedback on the personalized benefits of choices, and a web-based tool for providers to view patient risk, patient choice, and expert advice. Although medication was typically the intervention resulting in the greatest risk reduction, the majority of patients preferred dietary and other lifestyle changes. Patients generally favored the opportunity to make and communicate choices. However, providers only viewed patient choice data in 20% of the encounters. Translation of the SDM process was successful for patients and the difference between patient choice and optimal risk reduction points to the importance of engaging in an SDM process. Lack of engagement by providers may be due to "alert fatigue" or to the failure of the SDM process to improve efficiency in the office visit.
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Affiliation(s)
- J B Jones
- Center for Health Research, Geisinger Clinic, Danville, PA USA
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1376
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Zhang Y, Wölfle T, Rospert S. Interaction of nascent chains with the ribosomal tunnel proteins Rpl4, Rpl17, and Rpl39 of Saccharomyces cerevisiae. J Biol Chem 2013; 288:33697-33707. [PMID: 24072706 DOI: 10.1074/jbc.m113.508283] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
As translation proceeds, nascent polypeptides pass through an exit tunnel that traverses the large ribosomal subunit. Three ribosomal proteins, termed Rpl4, Rpl17, and Rpl39 expose domains to the interior of the exit tunnel of eukaryotic ribosomes. Here we generated ribosome-bound nascent chains in a homologous yeast translation system to analyze contacts between the tunnel proteins and nascent chains. As model proteins we employed Dap2, which contains a hydrophobic signal anchor (SA) segment, and the chimera Dap2α, in which the SA was replaced with a hydrophilic segment, with the propensity to form an α-helix. Employing a newly developed FLAG exposure assay, we find that the nascent SA segment but not the hydrophilic segment adopted a stable, α-helical structure within the tunnel when the most C-terminal SA residue was separated by 14 residues from the peptidyl transferase center. Using UV cross-linking, antibodies specifically recognizing Rpl17 or Rpl39, and a His6-tagged version of Rpl4, we established that all three tunnel proteins of yeast contact the SA, whereas only Rpl4 and Rpl39 also contact the hydrophilic segment. Consistent with the localization of the tunnel exposed domains of Rpl17 and Rpl39, the SA was in contact with Rpl17 in the middle region and with Rpl39 in the exit region of the tunnel. In contrast, Rpl4 was in contact with nascent chain residues throughout the ribosomal tunnel.
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Affiliation(s)
- Ying Zhang
- Institute of Biochemistry and Molecular Biology, ZBMZ Centre for Biochemistry and Molecular Cell Research, University of Freiburg, Stefan-Meier-Strasse 17, D-79104 Freiburg, Germany; Centre for Biological Signalling Studies (BIOSS), University of Freiburg, D-79104 Freiburg, Germany
| | - Tina Wölfle
- Institute of Biochemistry and Molecular Biology, ZBMZ Centre for Biochemistry and Molecular Cell Research, University of Freiburg, Stefan-Meier-Strasse 17, D-79104 Freiburg, Germany
| | - Sabine Rospert
- Institute of Biochemistry and Molecular Biology, ZBMZ Centre for Biochemistry and Molecular Cell Research, University of Freiburg, Stefan-Meier-Strasse 17, D-79104 Freiburg, Germany; Centre for Biological Signalling Studies (BIOSS), University of Freiburg, D-79104 Freiburg, Germany.
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1377
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Abstract
β-cells of the pancreatic islets are highly specialized and high-throughput units for the production of insulin, the key hormone for maintenance of glucose homeostasis. Elevation of extracellular glucose and/or GLP-1 levels triggers a rapid upregulation of insulin biosynthesis through the activation of post-transcriptional mechanisms. RNA-binding proteins are emerging as key factors in the regulation of these mechanisms as well as in other aspects of β-cell function and glucose homeostasis at large, and thus may be implicated in the pathogenesis of diabetes. Here we review current research in the field, with a major emphasis on RNA-binding proteins that control biosynthesis of insulin and other components of the insulin secretory granules by modulating the stability and translation of their mRNAs.
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1378
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Fu X, Shi X, Yan L, Zhang H, Chang Z. In vivo substrate diversity and preference of small heat shock protein IbpB as revealed by using a genetically incorporated photo-cross-linker. J Biol Chem 2013; 288:31646-54. [PMID: 24045939 DOI: 10.1074/jbc.m113.501817] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Small heat shock proteins (sHSPs), as ubiquitous molecular chaperones found in all forms of life, are known to be able to protect cells against stresses and suppress the aggregation of a variety of model substrate proteins under in vitro conditions. Nevertheless, it is poorly understood what natural substrate proteins are protected by sHSPs in living cells. Here, by using a genetically incorporated photo-cross-linker (p-benzoyl-l-phenylalanine), we identified a total of 95 and 54 natural substrate proteins of IbpB (an sHSP from Escherichia coli) in living cells with and without heat shock, respectively. Functional profiling of these proteins (110 in total) suggests that IbpB, although binding to a wide range of cellular proteins, has a remarkable substrate preference for translation-related proteins (e.g. ribosomal proteins and amino-acyl tRNA synthetases) and moderate preference for metabolic enzymes. Furthermore, these two classes of proteins were found to be more prone to aggregation and/or inactivation in cells lacking IbpB under stress conditions (e.g. heat shock). Together, our in vivo data offer novel insights into the chaperone function of IbpB, or sHSPs in general, and suggest that the preferential protection on the protein synthesis machine and metabolic enzymes may dominantly contribute to the well known protective effect of sHSPs on cell survival against stresses.
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Affiliation(s)
- Xinmiao Fu
- From the State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking University, Beijing 100871 and
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1379
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Pytharopoulou S, Kournoutou GG, Leotsinidis M, Georgiou CD, Kalpaxis DL. Cadmium versus copper toxicity: insights from an integrated dissection of protein synthesis pathway in the digestive glands of mussel Mytilus galloprovincialis. J Hazard Mater 2013; 260:263-71. [PMID: 23770617 DOI: 10.1016/j.jhazmat.2013.05.031] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Revised: 05/15/2013] [Accepted: 05/17/2013] [Indexed: 05/23/2023]
Abstract
The main purpose of this study was to investigate the impact of metal-mediated stress on the protein-synthesis pathway in mussels. To this end, mussels (Mytilus galloprovincialis) underwent a 15 days exposure to 100 μg/L Cu(2+) or Cd(2+). Both metals, in particular Cd(2+), accumulated in mussel digestive glands and generated a specific status of oxidative-stress. Exposure of mussels to each metal resulted in 40% decrease of the tRNA-aminoacylation efficiency, at the end of exposure. Cu(2+) also caused a progressive loss in the capability of 40S-ribosomal subunits to form 48S pre-initiation complex, which reached 34% of the control at the end of exposure. Other steps of translation underwent less pronounced, but measurable damages. Mussels exposed to Cd(2+) for 5 days presented a similar pattern of translational dysfunctions in digestive glands, but during the following days of exposure the ribosomal efficiency was gradually restored. Meanwhile, metallothionein levels significantly increased, suggesting that upon Cd(2+)-mediated stress the protein-synthesizing activity was reorganized both quantitatively and qualitatively. Conclusively, Cd(2+) and Cu(2+) affect translation at several levels. However, the pattern of translational responses differs, largely depending on the capability of each metal to affect cytotoxic pathways in the tissues, such as induction of antioxidant defense and specific repair mechanisms.
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Affiliation(s)
- S Pytharopoulou
- Laboratory of Biochemistry, School of Medicine, University of Patras, 26504 Patras, Greece
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1380
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Soiferman D, Ayalon O, Weissman S, Saada A. The effect of small molecules on nuclear-encoded translation diseases. Biochimie 2013; 100:184-91. [PMID: 24012549 DOI: 10.1016/j.biochi.2013.08.024] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Accepted: 08/25/2013] [Indexed: 01/18/2023]
Abstract
The five complexes of the mitochondrial respiratory chain (MRC) supply most organs and tissues with ATP produced by oxidative phosphorylation (OXPHOS). Inherited mitochondrial diseases affecting OXPHOS dysfunction are heterogeneous; symptoms may present at any age and may affect a wide range of tissues, with many diseases giving rise to devastating multisystemic disorders resulting in neonatal death. Combined respiratory chain deficiency with normal complex II accounts for a third of all respiratory deficiencies; mutations in nuclear-encoded components of the mitochondrial translation machinery account for many cases. Although mutations have been identified in over 20 such genes and our understanding of the mitochondrial translation apparatus is increasing, to date no definitive cure for these disorders exists. We evaluated the effect of seven small molecules with reported therapeutic potential in fibroblasts of four patients with combined respiratory complex disorders, each harboring a known mutation in a different nuclear-encoded component of the mitochondrial translation machinery: EFTs, GFM1, MRPS22 and TRMU. Six mitochondrial parameters were screened as follows; growth in glucose-free medium, reactive oxygen species (ROS) production, ATP content, mitochondrial content, mitochondrial membrane potential and complex IV activity. It was clearly evident that each patient displayed an individual response and there was no universally beneficial compound. AICAR increased complex IV activity in GFM1 cells and increased ATP content in MRPS22 fibroblasts but was detrimental to TRMU, who benefitted from bezafibrate. Two antioxidants, ascorbate and N-acetylcysteine (NAC), significantly improved cell growth, ATP content and mitochondrial membrane potential and decreased levels of intracellular reactive oxygen species (ROS) in EFTs fibroblasts. This study presents an expanded repertoire of assays that can be performed using the microtiter screening system with a small number of patients' fibroblasts and highlights some therapeutic options while providing additional evidence for the importance of personalized medicine in mitochondrial disorders.
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Affiliation(s)
- Devorah Soiferman
- Monique and Jacques Roboh Department of Genetic Research, Hadassah-Hebrew University Medical Center, Jerusalem, Israel; Department of Genetics and Metabolic Diseases, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Oshrat Ayalon
- Department of Genetics and Metabolic Diseases, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Sarah Weissman
- Department of Genetics and Metabolic Diseases, Hadassah-Hebrew University Medical Center, Jerusalem, Israel
| | - Ann Saada
- Monique and Jacques Roboh Department of Genetic Research, Hadassah-Hebrew University Medical Center, Jerusalem, Israel; Department of Genetics and Metabolic Diseases, Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
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1381
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Abstract
Universal genetic codes are degenerated with 61 codons specifying 20 amino acids, thus creating synonymous codons for a single amino acid. Synonymous codons have been shown to affect protein properties in a given organism. To address this issue and explore how Escherichia coli selects its "codon-preferred" DNA template(s) for synthesis of proteins with required properties, we have designed synonymous codon libraries based on an antibody (scFv) sequence and carried out bacterial expression and screening for variants with altered properties. As a result, 342 codon variants have been identified, differing significantly in protein solubility and functionality while retaining the identical original amino acid sequence. The soluble expression level varied from completely insoluble aggregates to a soluble yield of ~2.5 mg/liter, whereas the antigen-binding activity changed from no binding at all to a binding affinity of > 10(-8) m. Not only does our work demonstrate the involvement of genetic codes in regulating protein synthesis and folding but it also provides a novel screening strategy for producing improved proteins without the need to substitute amino acids.
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Affiliation(s)
- Shaoliang Hu
- From the School of Life Sciences, Tsinghua University, Beijing 100084
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1382
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Camenares D, Dulebohn DP, Svetlanov A, Karzai AW. Active and accurate trans- translation requires distinct determinants in the C-terminal tail of SmpB protein and the mRNA-like domain of transfer messenger RNA (tmRNA). J Biol Chem 2013; 288:30527-30542. [PMID: 23986442 DOI: 10.1074/jbc.m113.503896] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Unproductive ribosome stalling in eubacteria is resolved by the actions of SmpB protein and transfer messenger (tm) RNA. We examined the functional significance of conserved regions of SmpB and tmRNA to the trans-translation process. Our investigations reveal that the N-terminal 20 residues of SmpB, which are located near the ribosomal decoding center, are dispensable for all known SmpB activities. In contrast, a set of conserved residues that reside at the junction between the tmRNA-binding core and the C-terminal tail of SmpB play an important role in tmRNA accommodation. Our data suggest that the highly conserved glycine 132 acts as a flexible hinge that enables movement of the C-terminal tail, thus permitting proper positioning and establishment of the tmRNA open reading frame (ORF) as the surrogate template. To gain further insights into the function of the SmpB C-terminal tail, we examined the tagging activity of hybrid variants of tmRNA and the SmpB protein, in which the tmRNA ORF or the SmpB C-terminal tail was substituted with the equivalent but highly divergent sequences from Francisella tularensis. We observed that the hybrid tmRNA was active but resulted in less accurate selection of the resume codon. Cognate hybrid SmpB was necessary to restore activity. Furthermore, accurate tagging was observed when the identity of the resume codon was reverted from GGC to GCA. Taken together, these data suggest that the engagement of the tmRNA ORF and the selection of the correct translation resumption point are distinct activities that are influenced by independent tmRNA and SmpB determinants.
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Affiliation(s)
- Devin Camenares
- From the Department of Biochemistry and Cell Biology and; Center for Infectious Diseases, Stony Brook University, Stony Brook, New York 11794
| | | | - Anton Svetlanov
- From the Department of Biochemistry and Cell Biology and; Center for Infectious Diseases, Stony Brook University, Stony Brook, New York 11794
| | - A Wali Karzai
- From the Department of Biochemistry and Cell Biology and; Center for Infectious Diseases, Stony Brook University, Stony Brook, New York 11794.
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1383
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Eyler DE, Wehner KA, Green R. Eukaryotic release factor 3 is required for multiple turnovers of peptide release catalysis by eukaryotic release factor 1. J Biol Chem 2013; 288:29530-8. [PMID: 23963452 PMCID: PMC3795251 DOI: 10.1074/jbc.m113.487090] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Eukaryotic peptide release factor 3 (eRF3) is a conserved, essential gene in eukaryotes implicated in translation termination. We have systematically measured the contribution of eRF3 to the rates of peptide release with both saturating and limiting levels of eukaryotic release factor 1 (eRF1). Although eRF3 modestly stimulates the absolute rate of peptide release (∼5-fold), it strongly increases the rate of peptide release when eRF1 is limiting (>20-fold). This effect was generalizable across all stop codons and in a variety of contexts. Further investigation revealed that eRF1 remains associated with ribosomal complexes after peptide release and subunit dissociation and that eRF3 promotes the dissociation of eRF1 from these post-termination complexes. These data are consistent with models where eRF3 principally affects binding interactions between eRF1 and the ribosome, either prior to or subsequent to peptide release. A role for eRF3 as an escort for eRF1 into its fully accommodated state is easily reconciled with its close sequence similarity to the translational GTPase EFTu.
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Affiliation(s)
- Daniel E Eyler
- From the Howard Hughes Medical Institute and the Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
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1384
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Rackham O, Filipovska A. Supernumerary proteins of mitochondrial ribosomes. Biochim Biophys Acta Gen Subj 2013; 1840:1227-32. [PMID: 23958563 DOI: 10.1016/j.bbagen.2013.08.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2013] [Revised: 08/08/2013] [Accepted: 08/13/2013] [Indexed: 01/13/2023]
Abstract
BACKGROUND Messenger RNAs encoded by mitochondrial genomes are translated on mitochondrial ribosomes that have unique structure and protein composition compared to prokaryotic and cytoplasmic ribosomes. Mitochondrial ribosomes are a patchwork of core proteins that share homology with prokaryotic ribosomal proteins and new, supernumerary proteins that can be unique to different organisms. In mammals, there are specific supernumerary ribosomal proteins that are not present in other eukaryotes. SCOPE OF REVIEW Here we discuss the roles of supernumerary proteins in the regulation of mitochondrial gene expression and compare them among different eukaryotic systems. Furthermore, we consider if differences in the structure and organization of mitochondrial genomes may have contributed to the acquisition of mitochondrial ribosomal proteins with new functions. MAJOR CONCLUSIONS The distinct and diverse compositions of mitochondrial ribosomes illustrate the high evolutionary divergence found between mitochondrial genetic systems. GENERAL SIGNIFICANCE Elucidating the role of the organism-specific supernumerary proteins may provide a window into the regulation of mitochondrial gene expression through evolution in response to distinct evolutionary paths taken by mitochondria in different organisms. This article is part of a Special Issue entitled Frontiers of Mitochondrial Research.
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Affiliation(s)
- Oliver Rackham
- Western Australian Institute for Medical Research, Western Australia 6000, Australia; School of Chemistry and Biochemistry, The University of Western Australia, Western Australia 6009, Australia
| | - Aleksandra Filipovska
- Western Australian Institute for Medical Research, Western Australia 6000, Australia; School of Chemistry and Biochemistry, The University of Western Australia, Western Australia 6009, Australia.
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1385
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Comyn SA, Chan GT, Mayor T. False start: co translational protein ubiquitination and cytosolic protein quality control. J Proteomics 2013; 100:92-101. [PMID: 23954725 DOI: 10.1016/j.jprot.2013.08.005] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2013] [Revised: 08/02/2013] [Accepted: 08/04/2013] [Indexed: 12/18/2022]
Abstract
UNLABELLED Maintaining proteostasis is crucial to cells given the toxic potential of misfolded proteins and aggregates. To this end, cells rely on a number of quality control pathways that survey proteins both during, as well as after synthesis to prevent protein aggregation, promote protein folding, and to target terminally misfolded proteins for degradation. In eukaryotes, the ubiquitin proteasome system plays a critical role in protein quality control by selectively targeting proteins for degradation. Recent studies have added to our understanding of cytosolic protein quality control, particularly in the area of cotranslational protein ubiquitination, and suggest that overlap exists across co- and post-translational protein quality control networks. Here, we review recent advances made in the area of cytoplasmic protein quality control with an emphasis on the pathways involved in cotranslational degradation of eukaryotic cytosolic proteins. BIOLOGICAL SIGNIFICANCE Protein homeostasis, or proteostasis, encompasses the systems required by the cell for the generation and maintenance of the correct levels, conformational state, distribution, and degradation of its proteome. One of the challenges faced by the cell in maintaining proteostasis is the presence of misfolded proteins. Cells therefore have a number of protein quality control pathways to aid in folding or mediate the degradation of misfolded proteins. The ubiquitin proteasome system in particular plays a critical role in protein quality control by selectively targeting proteins for degradation. Nascent polypeptides can be ubiquitinated cotranslationally, however to what extent and how this is used by the cell as a quality control mechanism has, until recently, remained relatively unclear. The picture now emerging is one of two quality control networks: one that recognizes nascent polypeptides on stalled ribosomes and another that targets actively translating polypeptides that misfold, failing to attain their native conformation. These studies underscore the important balance between cotranslational protein folding and degradation in the maintenance of protein homeostasis. In this review we summarize recent advances made in the area of cytoplasmic protein quality control with an emphasis on pathways involved in cotranslational degradation of eukaryotic cytosolic proteins. This article is part of a Special Issue entitled: Can Proteomics Fill the Gap Between Genomics and Phenotypes?
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Affiliation(s)
- Sophie A Comyn
- Department of Biochemistry and Molecular Biology, Center for High-Throughput Biology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Gerard T Chan
- Department of Biochemistry and Molecular Biology, Center for High-Throughput Biology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Thibault Mayor
- Department of Biochemistry and Molecular Biology, Center for High-Throughput Biology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
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1386
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Shepherd J, Ibba M. Direction of aminoacylated transfer RNAs into antibiotic synthesis and peptidoglycan-mediated antibiotic resistance. FEBS Lett 2013; 587:2895-904. [PMID: 23907010 DOI: 10.1016/j.febslet.2013.07.036] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2013] [Accepted: 07/17/2013] [Indexed: 12/30/2022]
Abstract
Prokaryotic aminoacylated-transfer RNAs often need to be efficiently segregated between translation and other cellular biosynthetic pathways. Many clinically relevant bacteria, including Streptococcus pneumoniae, Staphylococcus aureus, Enterococcus faecalis and Pseudomonas aeruginosa direct some aminoacylated-tRNA species into peptidoglycan biosynthesis and/or membrane phospholipid modification. Subsequent indirect peptidoglycan cross-linkage or change in membrane permeability is often a prerequisite for high-level antibiotic resistance. In Streptomycetes, aminoacylated-tRNA species are used for antibiotic synthesis as well as antibiotic resistance. The direction of coding aminoacylated-tRNA molecules away from translation and into antibiotic resistance and synthesis pathways are discussed in this review.
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Affiliation(s)
- Jennifer Shepherd
- Department of Microbiology and Center for RNA Biology, Ohio State University, Columbus, OH 43210-1292, USA
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1387
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Abstract
Letm1 is a conserved protein in eukaryotes bearing energized mitochondria. Hemizygous deletion of its gene has been implicated in symptoms of the human disease Wolf-Hirschhorn syndrome. Studies almost exclusively performed in opisthokonts have attributed several roles to Letm1, including maintaining mitochondrial morphology, mediating either calcium or potassium/proton antiport, and facilitating mitochondrial translation. We address the ancestral function of Letm1 in the highly diverged protist and significant pathogen, Trypanosoma brucei. We demonstrate that Letm1 is involved in maintaining mitochondrial volume via potassium/proton exchange across the inner membrane. This role is essential in the vector-dwelling procyclic and mammal-infecting bloodstream stages as well as in Trypanosoma brucei evansi, a form of the latter stage lacking an organellar genome. In the pathogenic bloodstream stage, the mitochondrion consumes ATP to maintain an energized state, whereas that of T. brucei evansi also lacks a conventional proton-driven membrane potential. Thus, Letm1 performs its function in different physiological states, suggesting that ion homeostasis is among the few characterized essential pathways of the mitochondrion at this T. brucei life stage. Interestingly, Letm1 depletion in the procyclic stage can be complemented by exogenous expression of its human counterpart, highlighting the conservation of protein function between highly divergent species. Furthermore, although mitochondrial translation is affected upon Letm1 ablation, it is an indirect consequence of K(+) accumulation in the matrix.
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Affiliation(s)
- Hassan Hashimi
- From the Institute of Parasitology, Biology Centre, Czech Academy of Sciences and
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1388
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Martin-Marcos P, Nanda J, Luna RE, Wagner G, Lorsch JR, Hinnebusch AG. β-Hairpin loop of eukaryotic initiation factor 1 (eIF1) mediates 40 S ribosome binding to regulate initiator tRNA(Met) recruitment and accuracy of AUG selection in vivo. J Biol Chem 2013; 288:27546-27562. [PMID: 23893413 DOI: 10.1074/jbc.m113.498642] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Recognition of the translation initiation codon is thought to require dissociation of eIF1 from the 40 S ribosomal subunit, enabling irreversible GTP hydrolysis (Pi release) by the eIF2·GTP·Met-tRNAi ternary complex (TC), rearrangement of the 40 S subunit to a closed conformation incompatible with scanning, and stable binding of Met-tRNAi to the P site. The crystal structure of a Tetrahymena 40 S·eIF1 complex revealed several basic amino acids in eIF1 contacting 18 S rRNA, and we tested the prediction that their counterparts in yeast eIF1 are required to prevent premature eIF1 dissociation from scanning ribosomes at non-AUG triplets. Supporting this idea, substituting Lys-60 in helix α1, or either Lys-37 or Arg-33 in β-hairpin loop-1, impairs binding of yeast eIF1 to 40 S·eIF1A complexes in vitro, and it confers increased initiation at UUG codons (Sui(-) phenotype) or lethality, in a manner suppressed by overexpressing the mutant proteins or by an eIF1A mutation (17-21) known to impede eIF1 dissociation in vitro. The eIF1 Sui(-) mutations also derepress translation of GCN4 mRNA, indicating impaired ternary complex loading, and this Gcd(-) phenotype is likewise suppressed by eIF1 overexpression or the 17-21 mutation. These findings indicate that direct contacts of eIF1 with 18 S rRNA seen in the Tetrahymena 40 S·eIF1 complex are crucial in yeast to stabilize the open conformation of the 40 S subunit and are required for rapid TC loading and ribosomal scanning and to impede rearrangement to the closed complex at non-AUG codons. Finally, we implicate the unstructured N-terminal tail of eIF1 in blocking rearrangement to the closed conformation in the scanning preinitiation complex.
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Affiliation(s)
- Pilar Martin-Marcos
- Laboratory of Gene Regulation and Development, Eunice K. Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892
| | - Jagpreet Nanda
- Department of Biophysics and Biophysical Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205
| | - Rafael E Luna
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115
| | - Gerhard Wagner
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115
| | - Jon R Lorsch
- Department of Biophysics and Biophysical Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
| | - Alan G Hinnebusch
- Laboratory of Gene Regulation and Development, Eunice K. Shriver NICHD, National Institutes of Health, Bethesda, Maryland 20892.
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1389
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Giampetruzzi A, Carson JH, Barbarese E. FMRP and myelin protein expression in oligodendrocytes. Mol Cell Neurosci 2013; 56:333-41. [PMID: 23891804 DOI: 10.1016/j.mcn.2013.07.009] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Revised: 06/19/2013] [Accepted: 07/21/2013] [Indexed: 11/15/2022] Open
Abstract
Fragile X syndrome (FXS) is caused by lack of expression of fragile X mental retardation protein (FMRP), the product of the Fmr1 gene. In many cases FXS is associated with abnormalities in CNS myelination. Although FMRP is expressed in oligodendrocyte progenitor cells and immature oligodendrocytes (OLGs) previous studies have not detected it in mature, myelin-producing OLGs. FMRP represses translation of myelin basic protein (MBP) RNA in vitro and is believed to prevent premature MBP expression in immature OLGs. Lack of FMRP in FXS could lead to premature myelination and/or myelin abnormalities. Here we show that FMRP is expressed in mature, MBP-positive OLGs of rodents and in MBP-positive human OLGs. We confirm that FMRP is a translational repressor of MBP mRNA in vitro, but at concentrations likely too high to be physiologically relevant in vivo. We find MBP expression in cultured Fmr1 KO OLGs to be similar to wild type, and expression of MBP and other myelin proteins in brain homogenates of the Fmr1 KO mouse to be similar to wild type before, during, and after the period of active myelination. These results suggest that while FMRP is expressed in mature OLGs, myelin abnormalities caused by lack of FMRP expression in FXS are not recapitulated in rodents.
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Affiliation(s)
- Anthony Giampetruzzi
- Department of Neuroscience, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, CT 06030-3401, USA.
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1390
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Roberts JM, Bell MJ. If we know so much about preeclampsia, why haven't we cured the disease? J Reprod Immunol 2013; 99:1-9. [PMID: 23890710 DOI: 10.1016/j.jri.2013.05.003] [Citation(s) in RCA: 131] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2012] [Revised: 05/15/2013] [Accepted: 05/16/2013] [Indexed: 11/27/2022]
Abstract
Preeclampsia has been recognized for at least 100 years. In the last 20 years, the consideration of the disorder as more than simply hypertension in pregnancy has led to an explosion in knowledge about preeclampsia pathophysiology. It is now evident that for most cases of preeclampsia, the root cause is the placenta. Relatively reduced placental perfusion leads to inflammation, oxidative stress, and endoplasmic reticulum stress, which converge to modify maternal physiology, with endothelium an important target. Although preeclampsia is characteristically diagnosed in the last third of pregnancy, it is evident that many of these pathophysiological changes can be detected long before clinically evident disease. Furthermore, it is evident that the "maternal constitution," including genetic, behavioral, and metabolic factors, influences the maternal response to the abnormal placentation of preeclampsia. These insights would seem to provide a guide for the prediction of the disorder in early pregnancy, along with targets for intervention. However, this has not been the case. Predictive tests guided by this knowledge do not predict well and several interventions guided by the expanded understanding of pathophysiology do not prevent the disease. We propose that these failures are secondary to the fact that preeclampsia is more than one disorder. Further, we suggest that future progress toward prediction and prevention will require research guided by this concept.
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Affiliation(s)
- James M Roberts
- Magee-Womens Research Institute, University of Pittsburgh, Pittsburgh, PA, USA; Department of Obstetrics Gynecology and Reproductive Sciences, University of Pittsburgh, Pittsburgh, PA, USA; Department of Epidemiology, University of Pittsburgh, Pittsburgh, PA, USA; Department of Clinical and Translational Research, University of Pittsburgh, Pittsburgh, PA, USA.
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1391
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Dujeancourt L, Richter R, Chrzanowska-Lightowlers ZM, Bonnefoy N, Herbert CJ. Interactions between peptidyl tRNA hydrolase homologs and the ribosomal release factor Mrf1 in S. pombe mitochondria. Mitochondrion 2013; 13:871-80. [PMID: 23892058 PMCID: PMC3919214 DOI: 10.1016/j.mito.2013.07.115] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2012] [Revised: 06/19/2013] [Accepted: 07/18/2013] [Indexed: 11/22/2022]
Abstract
Mitochondrial translation synthesizes key subunits of the respiratory complexes. In Schizosaccharomyces pombe, strains lacking Mrf1, the mitochondrial stop codon recognition factor, are viable, suggesting that other factors can play a role in translation termination. S. pombe contains four predicted peptidyl tRNA hydrolases, two of which (Pth3 and Pth4), have a GGQ motif that is conserved in class I release factors. We show that high dosage of Pth4 can compensate for the absence of Mrf1 and loss of Pth4 exacerbates the lack of Mrf1. Also Pth4 is a component of the mitochondrial ribosome, suggesting that it could help recycling stalled ribosomes. In S. pombe the peptidyl tRNA hydrolases Pth3 and Pth4 are mitochondrial proteins. Pth3 and Pth4 are associated with the mitochondrial ribosome and the large subunit. Deletion of pth4 and mrf1, encoding the mitochondrial release factor, is co-lethal. Over-expression of pth4 compensates for the deletion of mrf1. Pth4 can act as a release factor in S. pombe mitochondria.
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Affiliation(s)
- Laurent Dujeancourt
- Centre de Génétique Moléculaire, UPR3404, FRC3115, Avenue de la Terrasse, 91198 Gif-sur-Yvette Cedex, France
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1392
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Abstract
Streptococcus pneumoniae is a causative agent of nosocomial infections such as pneumonia, meningitis, and septicemia. Penicillin resistance in S. pneumoniae depends in part upon MurM, an aminoacyl-tRNA ligase that attaches L-serine or L-alanine to the stem peptide lysine of Lipid II in cell wall peptidoglycan. To investigate the exact substrates the translation machinery provides MurM, quality control by alanyl-tRNA synthetase (AlaRS) was investigated. AlaRS mischarged serine and glycine to tRNA(Ala), as observed in other bacteria, and also transferred alanine, serine, and glycine to tRNA(Phe). S. pneumoniae tRNA(Phe) has an unusual U4:C69 mismatch in its acceptor stem that prevents editing by phenylalanyl-tRNA synthetase (PheRS), leading to the accumulation of misaminoacylated tRNAs that could serve as substrates for translation or for MurM. Although the peptidoglycan layer of S. pneumoniae tolerates a combination of both branched and linear muropeptides, deletion of MurM results in a reversion to penicillin sensitivity in strains that were previously resistant. However, because MurM is not required for cell viability, the reason for its functional conservation across all strains of S. pneumoniae has remained elusive. We now show that MurM can directly function in translation quality control by acting as a broad specificity lipid-independent trans editing factor that deacylates tRNA. This activity of MurM does not require the presence of its second substrate, Lipid II, and can functionally substitute for the activity of widely conserved editing domain homologues of AlaRS, termed AlaXPs proteins, which are themselves absent from S. pneumoniae.
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Affiliation(s)
| | - Michael Ibba
- From the Department of Microbiology and; Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210.
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1393
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Faes K, Tournaye H, Goethals L, Lahoutte T, Hoorens A, Goossens E. Testicular cell transplantation into the human testes. Fertil Steril 2013; 100:981-8. [PMID: 23850302 DOI: 10.1016/j.fertnstert.2013.06.016] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Revised: 05/27/2013] [Accepted: 06/11/2013] [Indexed: 01/15/2023]
Abstract
OBJECTIVE To translate spermatogonial stem cell (SSC) transplantation towards a clinical application. DESIGN Mouse green fluorescent protein (GFP)-positive testicular cells were labeled with (99m)technetium and microbubbles. These labeled cells were injected into the rete testis of isolated human testes under ultrasound guidance. Three different conditions were tested: 1) 800 μL of a 20 million cells/mL suspension; 2) 800 μL of a 10 million cells/mL suspension; and 3) 1,400 μL of a 10 million cells/mL suspension. After injection, the human cadaver testes were analyzed with the use of single-photon-emission computerized tomography (SPECT) imaging and histology. SETTING Laboratory research environment. PATIENT(S) Cadaver testes, obtained from autopsies at the pathology department. INTERVENTION(S) Ultrasound-guided injection of mouse GFP-positive testicular cells. MAIN OUTCOME MEASURE(S) Presence of radioactive-labeled cells in the human cadaver testes and GFP-positive cells in the seminiferous tubules. RESULT(S) In all of the experimental groups, GFP-positive cells were observed in the seminiferous tubules, near and far from the rete testis, but also in the interstitium. On SPECT, significant difference was seen between the group injected with 800 μL of a 20 million cells/mL suspension (1,654.6 ± 907.6 mm³) and the group injected with 1,400 μL of a 10 million cells/mL suspension (3,614.9 ± 723.1 mm³). No significant difference was reached in the group injected with 800 μL of a 10 million cells/mL suspension. CONCLUSION(S) Injecting cells in the human cadaver testis is feasible, but further optimization is required.
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Affiliation(s)
- Katrien Faes
- Biology of the Testis, Research Laboratory for Embryology and Genetics, Vrije Universiteit Brussel, Brussels, Belgium.
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1394
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Abstract
The sobemoviruses have one of the smallest of all known RNA virus genomes. ORF1 encodes P1 which plays a role in suppression of silencing and virus movement, ORFs 2a and 2b encode the replicational polyproteins P2a and P2ab, and ORF3 encodes the coat protein. Translation of ORF2a from the genomic RNA is dependent on a leaky scanning mechanism. We report the presence of an additional ORF (ORFx), conserved in all sobemoviruses. ORFx overlaps the 5′ end of ORF2a in the +2 reading frame and also extends some distance upstream of ORF2a. ORFx lacks an AUG initiation codon and its expression is predicted to depend on low level initiation at near-cognate non-AUG codons, such as CUG, by a proportion of the ribosomes that are scanning the region between the ORF1 and ORF2a initiation codons. Mutations that disrupt translation of ORFx in turnip rosette virus prevent the establishment of infection. The plant-infecting sobemoviruses have a 4–4.5 kb genome with four know coding ORFs. We report an additional ORF (ORFx) that is conserved in all sobemoviruses. Translation of ORFx is predicted to depend on leaky scanning and non-AUG initiation. Mutations that disrupt translation of ORFx prevent the establishment of infection.
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Affiliation(s)
- Roger Ling
- Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
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1395
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MANAVI S, OLYAEE MANESH A, YAZDANI S, SHAMS L, NASIRI T, SHIRVANI A, EMAMI RAZAVI H. Model for implementing evidence based health care system in iran. Iran J Public Health 2013; 42:758-66. [PMID: 24427754 PMCID: PMC3881621] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/05/2013] [Accepted: 06/22/2013] [Indexed: 11/04/2022]
Abstract
BACKGROUND Regarding the role and importance of paradigm of evidence based practice and its remarkable impact on the effectiveness and efficiency of clinical services and healthcare, development of an integrated system seems necessary in order to manage dispersed data and ensure using evidence in clinical decision making, thus the aim of this study was designing a model for implementing national system of evidence based health care in Iran. METHODOS THIS PAPER IS A STUDY OF COMPARATIVE TYPE WHICH HAS BEEN WRITTEN IN THREE STAGES: investigation of structure and process of evidence based practice in selected countries, investigation and analysis of current status in Iran in this regard and recommendation of strategies which make model implementation feasible in the country. Such methods as review of literature, focus group discussion and Delphi technique were used for investigation. RESULTS According to studies, insuring an evidence based practice culture in the country requires a system called National Evidence Based Health Care System which consists of three subsystems including national system of clinical knowledge management, national evidence-based practice system and integrated national network of clinical effectiveness. CONCLUSION The ultimate goal of health care system in every country is maintaining and improving community health. Achievement of this goal depends on effectiveness of delivered services and consistency of the services with national and local priorities. In order to achieve clinical effectiveness, the best practice should be realized in the country, implementation of which requires a set of macro and micro strategies enabling facilitation, promotion or guaranteeing clinical knowledge application in the country.
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Affiliation(s)
- Saeed MANAVI
- Dept. of Curative Affairs, Ministry of Health and Medical Education, Tehran, Iran
| | - Alireza OLYAEE MANESH
- Dept. of Curative Affairs, Ministry of Health and Medical Education, Tehran, Iran
- Dept. of Payment and Financing of Health System, National Institute for Health Research, Tehran University of Medical Sciences, Tehran, Iran
| | - Shahram YAZDANI
- School of Medical Education, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Lida SHAMS
- School of Public Health, Tehran University of Medical Sciences, Tehran, Iran
| | - Taha NASIRI
- Health Management Research Center, Baqiyatallah University of Medical Sciences, Tehran, Iran
| | - Armin SHIRVANI
- Dept. of Curative Affairs, Ministry of Health and Medical Education, Tehran, Iran
| | - Hasan EMAMI RAZAVI
- Dept. of Payment and Financing of Health System, National Institute for Health Research, Tehran University of Medical Sciences, Tehran, Iran
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1396
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Liu J, Stevens PD, Eshleman NE, Gao T. Protein phosphatase PPM1G regulates protein translation and cell growth by dephosphorylating 4E binding protein 1 (4E-BP1). J Biol Chem 2013; 288:23225-33. [PMID: 23814053 DOI: 10.1074/jbc.m113.492371] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Protein translation initiation is a tightly controlled process responding to nutrient availability and mitogen stimulation. Serving as one of the most important negative regulators of protein translation, 4E binding protein 1 (4E-BP1) binds to translation initiation factor 4E and inhibits cap-dependent translation in a phosphorylation-dependent manner. Although it has been demonstrated previously that the phosphorylation of 4E-BP1 is controlled by mammalian target of rapamycin in the mammalian target of rapamycin complex 1, the mechanism underlying the dephosphorylation of 4E-BP1 remains elusive. Here, we report the identification of PPM1G as the phosphatase of 4E-BP1. A coimmunoprecipitation experiment reveals that PPM1G binds to 4E-BP1 in cells and that purified PPM1G dephosphorylates 4E-BP1 in vitro. Knockdown of PPM1G in 293E and colon cancer HCT116 cells results in an increase in the phosphorylation of 4E-BP1 at both the Thr-37/46 and Ser-65 sites. Furthermore, the time course of 4E-BP1 dephosphorylation induced by amino acid starvation or mammalian target of rapamycin inhibition is slowed down significantly in PPM1G knockdown cells. Functionally, the amount of 4E-BP1 bound to the cap-dependent translation initiation complex is decreased when the expression of PPM1G is depleted. As a result, the rate of cap-dependent translation, cell size, and protein content are increased in PPM1G knockdown cells. Taken together, our study has identified protein phosphatase PPM1G as a novel regulator of cap-dependent protein translation by negatively controlling the phosphorylation of 4E-BP1.
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Affiliation(s)
- Jianyu Liu
- Markey Cancer Center, University of Kentucky, Lexington, Kentucky 40536-0509, USA
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1397
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Affiliation(s)
- Harry F Noller
- Center for Molecular Biology of RNA, Department of Molecular, Cell and Developmental Biology, University of California, Santa Cruz, California 95064, USA.
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1398
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Henson AL, Moore JB, Alard P, Wattenberg MM, Liu JM, Ellis SR. Mitochondrial function is impaired in yeast and human cellular models of Shwachman Diamond syndrome. Biochem Biophys Res Commun 2013; 437:29-34. [PMID: 23792098 DOI: 10.1016/j.bbrc.2013.06.028] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Accepted: 06/10/2013] [Indexed: 12/22/2022]
Abstract
Shwachman Diamond syndrome (SDS) is an inherited bone marrow failure syndrome typically characterized by neutropenia, exocrine pancreas dysfunction, metaphyseal chondrodysplasia, and predisposition to myelodysplastic syndrome and leukemia. SBDS, the gene affected in most cases of SDS, encodes a protein known to influence many cellular processes including ribosome biogenesis, mitotic spindle assembly, chemotaxis, and the regulation of reactive oxygen species production. The best characterized role for the SBDS protein is in the production of functional 60S ribosomal subunits. Given that a reduction in functional 60S subunits could impact on the translational output of cells depleted of SBDS we analyzed protein synthesis in yeast cells lacking SDO1, the ortholog of SBDS. Cells lacking SDO1 selectively increased the synthesis of POR1, the ortholog of mammalian VDAC1 a major anion channel of the mitochondrial outer membrane. Further studies revealed the cells lacking SDO1 were compromised in growth on non-fermentable carbon sources suggesting mitochondrial function was impaired. These observations prompted us to examine mitochondrial function in human cells where SBDS expression was reduced. Our studies indicate that reduced expression of SBDS decreases mitochondrial membrane potential and oxygen consumption and increases the production of reactive oxygen species. These studies indicate that mitochondrial function is also perturbed in cells expressing reduced amounts of SBDS and indicate that disruption of mitochondrial function may also contribute to SDS pathophysiology.
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Affiliation(s)
- Adrianna L Henson
- Department of Biochemistry and Molecular Biology, University of Louisville, Louisville, KY 40292, United States
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1399
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Sampath V, Liu B, Tafrov S, Srinivasan M, Rieger R, Chen EI, Sternglanz R. Biochemical characterization of Hpa2 and Hpa3, two small closely related acetyltransferases from Saccharomyces cerevisiae. J Biol Chem 2013; 288:21506-13. [PMID: 23775086 DOI: 10.1074/jbc.m113.486274] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Based on their sequences, the Saccharomyces cerevisiae Hpa2 and Hpa3 proteins are annotated as two closely related members of the Gcn5 acetyltransferase family. Here, we describe the biochemical characterization of Hpa2 and Hpa3 as bona fide acetyltransferases with different substrate specificities. Mutational and MALDI-TOF analyses showed that Hpa3 translation initiates primarily from Met-19 rather than the annotated start site, Met-1, with a minor product starting at Met-27. When expressed in Escherichia coli and assayed in vitro, Hpa2 and Hpa3 (from Met-19) acetylated histones and polyamines. Whereas Hpa2 acetylated histones H3 and H4 (at H3 Lys-14, H4 Lys-5, and H4 Lys-12), Hpa3 acetylated only histone H4 (at Lys-8). Additionally, Hpa2, but not Hpa3, acetylated certain small basic proteins. Hpa3, but not Hpa2, has been reported to acetylate D-amino acids, and we present results consistent with that. Overexpression of Hpa2 or Hpa3 is toxic to yeast cells. However, their deletions do not show any standard phenotypic defects. These results suggest that Hpa2 and Hpa3 are similar but distinct acetyltransferases that might have overlapping roles with other known acetyltransferases in vivo in acetylating histones and other small proteins.
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Affiliation(s)
- Vinaya Sampath
- Department of Biochemistry and Cell Biology, Stony Brook University, Stony Brook, New York 11794, USA
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1400
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Abstract
Translocation of tRNA-mRNA complex in the ribosome is an essential step in the elongation cycle of protein synthesis. However, some important issues concerning the molecular mechanism of the tRNA-mRNA translocation catalyzed by EF-G.GTP or by EF-G.GDPNP remain controversial. For example, can EF-G.GTP selectively bind to the hybrid pretranslocation state or bind to both the non-rotated pretranslocation and the hybrid pretranslocation states? Does the greater potency of EF-G in the presence of GTP rather than GDPNP in facilitating translocation derive from the effects on transition from the classical non-rotated to hybrid state (the first step of the translocation) or on transition from the hybrid to posttranslocation state (the second step)? Here, based on our proposed model, we study theoretically the dynamics of the tRNA-mRNA translocation through the ribosome catalyzed by EF-G.GTP and by EF-G.GDPNP. By comparing our theoretical results with the available experimental data, we show that EF-G.GTP can also bind to the classical non-rotated pretranslocation state and the greater potency of GTP hydrolysis in facilitating translocation of tRNA-mRNA complex derives from its effects on the second step of the translocation process.
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Affiliation(s)
- Ping Xie
- Key Laboratory of Soft Matter Physics and Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China.
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