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Sun D, Ji X, Jia Y, Huo D, Si S, Zeng L, Zhang Y, Niu L. LreEF1A4, a Translation Elongation Factor from Lilium regale, Is Pivotal for Cucumber Mosaic Virus and Tobacco Rattle Virus Infections and Tolerance to Salt and Drought. Int J Mol Sci 2020; 21:E2083. [PMID: 32197393 PMCID: PMC7139328 DOI: 10.3390/ijms21062083] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 03/14/2020] [Accepted: 03/16/2020] [Indexed: 11/17/2022] Open
Abstract
Eukaryotic translation elongation factors are implicated in protein synthesis across different living organisms, but their biological functions in the pathogenesis of cucumber mosaic virus (CMV) and tobacco rattle virus (TRV) infections are poorly understood. Here, we isolated and characterized a cDNA clone, LreEF1A4, encoding the alpha subunit of elongation factor 1, from a CMV-elicited suppression subtractive hybridization library of Lilium regale. The infection tests using CMV remarkably increased transcript abundance of LreEF1A4; however, it also led to inconsistent expression profiles of three other LreEF1A homologs (LreEF1A1-3). Protein modelling analysis revealed that the amino acid substitutions among four LreEF1As may not affect their enzymatic functions. LreEF1A4 was ectopically overexpressed in petunia (Petunia hybrida), and transgenic plants exhibited delayed leaf and flower senescence, concomitant with increased transcription of photosynthesis-related genes and reduced expression of senescence-associated genes, respectively. A compromised resistance to CMV and TRV infections was found in transgenic petunia plants overexpressing LreEF1A4, whereas its overexpression resulted in an enhanced tolerance to salt and drought stresses. Taken together, our data demonstrate that LreEF1A4 functions as a positive regulator in viral multiplication and plant adaption to high salinity and dehydration.
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Affiliation(s)
- Daoyang Sun
- College of Landscape Architecture and Arts, Northwest A&F University, Yangling 712100, China
| | - Xiaotong Ji
- College of Landscape Architecture and Arts, Northwest A&F University, Yangling 712100, China
| | - Yong Jia
- State Agricultural Biotechnology Centre, School of Veterinary and Life Sciences, Murdoch University, Perth 6150, Australia
| | - Dan Huo
- College of Landscape Architecture and Arts, Northwest A&F University, Yangling 712100, China
| | - Shiying Si
- College of Landscape Architecture and Arts, Northwest A&F University, Yangling 712100, China
| | - Lingling Zeng
- College of Landscape Architecture and Arts, Northwest A&F University, Yangling 712100, China
| | - Yanlong Zhang
- College of Landscape Architecture and Arts, Northwest A&F University, Yangling 712100, China
| | - Lixin Niu
- College of Landscape Architecture and Arts, Northwest A&F University, Yangling 712100, China
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Mechanism and Regulation of Protein Synthesis in Saccharomyces cerevisiae. Genetics 2017; 203:65-107. [PMID: 27183566 DOI: 10.1534/genetics.115.186221] [Citation(s) in RCA: 100] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2015] [Accepted: 02/24/2016] [Indexed: 12/18/2022] Open
Abstract
In this review, we provide an overview of protein synthesis in the yeast Saccharomyces cerevisiae The mechanism of protein synthesis is well conserved between yeast and other eukaryotes, and molecular genetic studies in budding yeast have provided critical insights into the fundamental process of translation as well as its regulation. The review focuses on the initiation and elongation phases of protein synthesis with descriptions of the roles of translation initiation and elongation factors that assist the ribosome in binding the messenger RNA (mRNA), selecting the start codon, and synthesizing the polypeptide. We also examine mechanisms of translational control highlighting the mRNA cap-binding proteins and the regulation of GCN4 and CPA1 mRNAs.
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Tarrant DJ, Stirpe M, Rowe M, Howard MJ, von der Haar T, Gourlay CW. Inappropriate expression of the translation elongation factor 1A disrupts genome stability and metabolism. J Cell Sci 2016; 129:4455-4465. [PMID: 27807005 PMCID: PMC5201016 DOI: 10.1242/jcs.192831] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2016] [Accepted: 10/26/2016] [Indexed: 02/02/2023] Open
Abstract
The translation elongation factor eEF1A is one of the most abundant proteins found within cells, and its role within protein synthesis is well documented. Levels of eEF1A are tightly controlled, with inappropriate expression linked to oncogenesis. However, the mechanisms by which increased eEF1A expression alters cell behaviour are unknown. Our analyses in yeast suggest that elevation of eEF1A levels leads to stabilisation of the spindle pole body and changes in nuclear organisation. Elevation of the eEF1A2 isoform also leads to altered nuclear morphology in cultured human cells, suggesting a conserved role in maintaining genome stability. Gene expression and metabolomic analyses reveal that the level of eEF1A is crucial for the maintenance of metabolism and amino acid levels in yeast, most likely because of its role in the control of vacuole function. Increased eEF1A2 levels trigger lysosome biogenesis in cultured human cells, also suggesting a conserved role within metabolic control mechanisms. Taken together, our data suggest that the control of eEF1A levels is important for the maintenance of a number of cell functions beyond translation and that its de-regulation might contribute to its oncogenic properties. Summary: The translation elongation factor eEF1A is elevated in some cancers. We use yeast and human cell models to show that eEF1A elevation leads to genome instability and metabolic alterations that might affect its oncogenic properties.
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Affiliation(s)
- Daniel J Tarrant
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK
| | - Mariarita Stirpe
- Department of Biology and Biotechnology, Sapienza, University of Rome, 00185 Rome, Italy
| | - Michelle Rowe
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK
| | - Mark J Howard
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK
| | - Tobias von der Haar
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK
| | - Campbell W Gourlay
- Kent Fungal Group, School of Biosciences, University of Kent, Canterbury, Kent CT2 7NJ, UK
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Yang S, Lu M, Chen Y, Meng D, Sun R, Yun D, Zhao Z, Lu D, Li Y. Overexpression of eukaryotic elongation factor 1 alpha-2 is associated with poorer prognosis in patients with gastric cancer. J Cancer Res Clin Oncol 2015; 141:1265-75. [DOI: 10.1007/s00432-014-1897-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2014] [Accepted: 12/15/2014] [Indexed: 01/14/2023]
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Specific antibody responses against membrane proteins of erythrocytes infected by Plasmodium falciparum of individuals briefly exposed to malaria. Malar J 2010; 9:276. [PMID: 20932351 PMCID: PMC2959075 DOI: 10.1186/1475-2875-9-276] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2010] [Accepted: 10/11/2010] [Indexed: 11/16/2022] Open
Abstract
Background Plasmodium falciparum infections could lead to severe malaria, principally in non-immune individuals as children and travellers from countries exempted of malaria. Severe malaria is often associated with the sequestration of P. falciparum-infected erythrocytes in deep micro-vascular beds via interactions between host endothelial receptors and parasite ligands expressed on the surface of the infected erythrocyte. Although, serological responses from individuals living in endemic areas against proteins expressed at surface of the infected erythrocyte have been largely studied, seldom data are available about the specific targets of antibody response from travellers. Methods In order to characterize antigens recognized by traveller sera, a comparison of IgG immune response against membrane protein extracts from uninfected and P. falciparum-infected red blood cells (iRBC), using immunoblots, was performed between non exposed individuals (n = 31) and briefly exposed individuals (BEI) (n = 38) to malaria transmission. Results Immune profile analysis indicated that eight protein bands from iRBC were significantly detected more frequently in the BEI group. Some of these antigenic proteins were identified by an original immuno-proteomic approach. Conclusion Collectively, these data may be useful to characterize the singular serological immune response against a primary malaria infection in individuals briefly exposed to transmission.
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Kim S, Coulombe PA. Emerging role for the cytoskeleton as an organizer and regulator of translation. Nat Rev Mol Cell Biol 2010; 11:75-81. [PMID: 20027187 DOI: 10.1038/nrm2818] [Citation(s) in RCA: 145] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The cytoskeleton is an intricate and dynamic fibrous network that has an essential role in the generation and regulation of cell architecture and cellular mechanical properties. The cytoskeleton also evolved as a scaffold that supports diverse biochemical pathways. Recent evidence favours the hypothesis that the cytoskeleton participates in the spatial organization and regulation of translation, at both the global and local level, in a manner that is crucial for cellular growth, proliferation and function.
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Affiliation(s)
- Seyun Kim
- The Solomon H. Snyder Department of Neuroscience, School of Medicine, Johns Hopkins University, Baltimore, Maryland 21205, USA
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Abstract
Cleavage furrows (CFs) have been isolated from dividing sea urchin eggs and the protein constituents have been analyzed by two-dimensional gel electrophoresis (Fujimoto & Mabuchi, J. Biochem. 122, 518-524, 1997). Two proteins of 51 and 32 kDa, respectively, have been found to be enriched in the CF preparation. Here, we show that these proteins are identical to the protein elongation factor 1alpha (EF-1alpha) and 1beta (EF-1beta), respectively. Furthermore, the CF 51-kDa protein is identical to the 51-kDa protein which had been isolated as a component of the microtubule organizing granules of mitotic sea urchin eggs. The 51-kDa protein bundles F-actin in vitro. This activity is suppressed by Ca(2+)/calmodulin or GTPgammaS. The 32-kDa protein binds EF-1alpha both in vitro and in cell extract, and is shown to suppress the F-actin-bundling activity of the 51-kDa protein. Microinjection of a monoclonal antibody against the 51-kDa protein or that of His-tagged 32-kDa protein into dividing sea urchin eggs at the onset of cleavage leads to failure of cytokinesis. These results strongly suggest that EF-1alpha is involved in maintenance of the structure of the contractile ring and EF-1beta regulates the F-actin-bundling activity of EF-1alpha.
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Affiliation(s)
- Hirotaka Fujimoto
- Department of Cell Biology, National Institute for Basic Biology, Okazaki, Aichi 444-8585, Japan
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Gale E, Li M. Midbrain dopaminergic neuron fate specification: Of mice and embryonic stem cells. Mol Brain 2008; 1:8. [PMID: 18826576 PMCID: PMC2569927 DOI: 10.1186/1756-6606-1-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2008] [Accepted: 09/30/2008] [Indexed: 01/08/2023] Open
Abstract
The midbrain dopaminergic (mDA) neurons of the substantia nigra and the ventral tegmental area play a fundamental role in the control of voluntary movement and the regulation of emotion, and are severely affected in Parkinson's disease. Recent advances in mouse genetics and vertebrate development have provided us with insight into the genetic cascades involved in the development of mDA neurons, including the induction of mDA neuron progenitors in the ventral mesencephalon, the specification of the mDA neuronal fate and the maintenance of postmitotic mDA neurons. In parallel, rapid progress has been made in the generation of DA neurons from pluripotent stem cells and the development of stem cell-based therapies for Parkinson's disease. Here, we summarize the new findings via the developmental progression of mDA neurons and outline how this knowledge has been exploited to develop novel paradigms for the in vitro generation of these neurons from embryonic stem cells.
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Affiliation(s)
- Emily Gale
- MRC Clinical Sciences Centre, Imperial College London, UK.
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Morita K, Bunai F, Numata O. Roles of three domains of Tetrahymena eEF1A in bundling F-actin. Zoolog Sci 2008; 25:22-9. [PMID: 18275242 DOI: 10.2108/zsj.25.22] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2007] [Accepted: 09/07/2007] [Indexed: 11/17/2022]
Abstract
The conventional role of eukaryotic elongation factor 1A (eEF1A) is to transport aminoacyl tRNA to the A site of ribosomes during the peptide elongation phase of protein synthesis. eEF1A also is involved in regulating the dynamics of microtubules and actin filaments in cytoplasm. In Tetrahymena, eEF1A forms homodimers and bundles F-actin. Ca(2+)/calmodulin (CaM) causes reversion of the eEF1A dimer to the monomer, which loosens F-actin bundling, and then Ca(2+)/CaM/eEF1A monomer complexes dissociate from F-actin. eEF1A consists of three domains in all eukaryotic species, but the individual roles of the Tetrahymena eEF1A domains in bundling F-actin are unknown. In this study, we investigated the interaction of each domain with F-actin, recombinant Tetrahymena CaM, and eEF1A itself in vitro, using three glutathione-S-transferase-domain fusion proteins (GST-dm1, -2, and -3). We found that only GST-dm3 bound to F-actin and influences dimer formation, but that all three domains bound to Tetrahymena CaM in a Ca(2+)-dependent manner. The critical Ca(2+) concentration for binding among three domains of eEF1A and CaM were < or =100 nM for domain 1, 100 nM to 1 microM for domain 3, and >1 microM for domain 2, whereas stimulation of and subsequent Ca(2+) influx through Ca(2+) channels raise the cellular Ca(2+) concentration from the basal level of approximately 100 nM to approximately 10 microM, suggesting that domain 3 has a pivotal role in Ca(2+)/CaM regulation of eEF1A.
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Affiliation(s)
- Kenya Morita
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan
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Gross SR, Kinzy TG. Improper organization of the actin cytoskeleton affects protein synthesis at initiation. Mol Cell Biol 2007; 27:1974-89. [PMID: 17178834 PMCID: PMC1820457 DOI: 10.1128/mcb.00832-06] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2006] [Revised: 06/14/2006] [Accepted: 12/07/2006] [Indexed: 11/20/2022] Open
Abstract
Although the actin cytoskeleton and the translation machinery are considered to be separate cellular complexes, growing evidence supports overlapping regulation of the two systems. Because of its interaction with actin, the eukaryotic translation elongation factor 1A (eEF1A) is proposed to be a regulator or link between these processes. Using a genetic approach with the yeast Saccharomyces cerevisiae, specific regions of eEF1A responsible for actin interactions and bundling were identified. Five new mutations were identified along one face of eEF1A. Dramatic changes in cell growth, cell morphology, and actin cable and patch formation as well as a unique effect on total translation in strains expressing the F308L or S405P eEF1A mutant form were observed. The translation effects do not correlate with reduced translation elongation but instead include an initiation defect. Biochemical analysis of the eEF1A mutant forms demonstrated reduced actin-bundling activity in vitro. Reduced total translation and/or the accumulation of 80S ribosomes in strains with either a mutation or a null allele of genes encoding actin itself or actin-regulating proteins Tpm1p, Mdm20p, and Bnirp/Bni1p was observed. Our data demonstrate that eEF1A, other actin binding proteins, and actin mutants affect translation initiation through the actin cytoskeleton.
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Affiliation(s)
- Stephane R Gross
- Department of Molecular Genetics, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway, NJ 08854, USA
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Xu WL, Wang XL, Wang H, Li XB. Molecular characterization and expression analysis of nine cotton GhEF1A genes encoding translation elongation factor 1A. Gene 2006; 389:27-35. [PMID: 17107762 DOI: 10.1016/j.gene.2006.09.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2006] [Revised: 08/29/2006] [Accepted: 09/13/2006] [Indexed: 10/24/2022]
Abstract
The translation elongation factor 1A, eEF1A, plays an important role in protein synthesis, catalyzing the binding of aminoacyl-tRNA to the A-site of the ribosome by a GTP-dependent mechanism. To investigate the role of eEF1A for protein synthesis in cotton fiber development, nine different cDNA clones encoding eukaryotic translation elongation factor 1A were isolated from cotton (Gossypium hirsutum) fiber cDNA libraries. The isolated genes (cDNAs) were designated cotton elongation factor 1A gene GhEF1A1, GhEF1A2, GhEF1A3, GhEF1A4, GhEF1A5, GhEF1A6, GhEF1A7, GhEF1A8, GhEF1A9, respectively. They share high sequence homology at nucleotide level (71-99% identity) in the coding region and at amino acid level (96-99% identity) among each other. Phylogenetic analysis demonstrated that the nine GhEF1A genes can be divided into 5-6 subfamilies, indicating the divergence occurred in structures of the genes as well as the deduced proteins during evolution. Real-time quantitative RT-PCR analysis revealed that GhEF1A genes are differentially expressed in different tissues/organs. Of the nine GhEF1A genes, five are expressed at relatively high levels in young fibers. Further analysis indicated that expressions of the GhEF1As in fiber are highly developmental-regulated, suggesting that protein biosynthesis is very active at the early fiber elongation.
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Affiliation(s)
- Wen-Liang Xu
- College of Life Sciences, HuaZhong Normal University, Wuhan 430079, P.R. China
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Tomlinson VAL, Newbery HJ, Wray NR, Jackson J, Larionov A, Miller WR, Dixon JM, Abbott CM. Translation elongation factor eEF1A2 is a potential oncoprotein that is overexpressed in two-thirds of breast tumours. BMC Cancer 2005; 5:113. [PMID: 16156888 PMCID: PMC1236916 DOI: 10.1186/1471-2407-5-113] [Citation(s) in RCA: 108] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2005] [Accepted: 09/12/2005] [Indexed: 11/11/2022] Open
Abstract
Background The tissue-specific translation elongation factor eEF1A2 was recently shown to be a potential oncogene that is overexpressed in ovarian cancer. Although there is no direct evidence for an involvement of eEF1A2 in breast cancer, the genomic region to which EEF1A2 maps, 20q13, is frequently amplified in breast tumours. We therefore sought to establish whether eEF1A2 expression might be upregulated in breast cancer. Methods eEF1A2 is highly similar (98%) to the near-ubiquitously expressed eEF1A1 (formerly known as EF1-α) making analysis with commercial antibodies difficult. We have developed specific anti-eEF1A2 antibodies and used them in immunohistochemical analyses of tumour samples. We report the novel finding that although eEF1A2 is barely detectable in normal breast it is moderately to strongly expressed in two-thirds of breast tumours. This overexpression is strongly associated with estrogen receptor positivity. Conclusion eEF1A2 should be considered as a putative oncogene in breast cancer that may be a useful diagnostic marker and therapeutic target for a high proportion of breast tumours. The oncogenicity of eEF1A2 may be related to its role in protein synthesis or to its potential non-canonical functions in cytoskeletal remodelling or apoptosis.
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Affiliation(s)
- Victoria AL Tomlinson
- Medical Genetics, School of Molecular and Clinical Medicine, University of Edinburgh, Molecular Medicine Centre, Western General Hospital, Edinburgh EH4 2XU, UK
| | - Helen J Newbery
- Medical Genetics, School of Molecular and Clinical Medicine, University of Edinburgh, Molecular Medicine Centre, Western General Hospital, Edinburgh EH4 2XU, UK
| | - Naomi R Wray
- Medical Genetics, School of Molecular and Clinical Medicine, University of Edinburgh, Molecular Medicine Centre, Western General Hospital, Edinburgh EH4 2XU, UK
| | - Juliette Jackson
- Breast Unit Research Group, Western General Hospital, Edinburgh EH4 2XU, UK
| | - Alexey Larionov
- Breast Unit Research Group, Western General Hospital, Edinburgh EH4 2XU, UK
| | - William R Miller
- Breast Unit Research Group, Western General Hospital, Edinburgh EH4 2XU, UK
| | - J Michael Dixon
- Breast Unit Research Group, Western General Hospital, Edinburgh EH4 2XU, UK
| | - Catherine M Abbott
- Medical Genetics, School of Molecular and Clinical Medicine, University of Edinburgh, Molecular Medicine Centre, Western General Hospital, Edinburgh EH4 2XU, UK
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Janse CJ, Haghparast A, Sperança MA, Ramesar J, Kroeze H, del Portillo HA, Waters AP. Malaria parasites lacking eef1a have a normal S/M phase yet grow more slowly due to a longer G1 phase. Mol Microbiol 2003; 50:1539-51. [PMID: 14651637 DOI: 10.1046/j.1365-2958.2003.03820.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Eukaryotic elongation factor 1A (eEF1A) plays a central role in protein synthesis, cell growth and morphology. Malaria parasites possess two identical genes encoding eEF1A (eef1aa and eef1ab). Using pbeef1a-Plasmodium berghei mutants that lack an eEF1a gene, we demonstrate that the level of eEF1A production affects the proliferation of blood stages and parasite fitness. Pbeef1a- parasites can complete the vertebrate and mosquito phases of the life cycle, but the growth phase of the asexual blood stages is extended by up to 20%. Analysis of the cell cycle by flow cytometry as well as transcriptional analyses revealed that the duration of the S and M phases and the number of daughter cells produced were not detectably affected, but that the G1 phase is elongated. Thus, as in budding yeast, a growth threshold must be achieved by blood-stage Plasmodium parasites to permit transition from G1 into S/M phase. Initial analyses indicate that transcriptional events associated with gametocyte development were not remarkably retarded. Insight into protein synthesis and its influence on cell proliferation might be used to generate slow-growing (attenuated) parasites.
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Affiliation(s)
- Chris J Janse
- Malaria Group, Department of Parasitology, Leiden University Medical Centre (LUMC), PO Box 9600, 2300 RC, Leiden, The Netherlands
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Hashemzadeh-Bonehi L, Curtis PS, Morley SJ, Thorpe JR, Pain VM. Overproduction of a conserved domain of fission yeast and mammalian translation initiation factor eIF4G causes aberrant cell morphology and results in disruption of the localization of F-actin and the organization of microtubules. Genes Cells 2003; 8:163-78. [PMID: 12581158 DOI: 10.1046/j.1365-2443.2003.00623.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
BACKGROUND The recruitment of mRNA for translation involves the assembly at the 5'cap of a complex of three initiation factors: the cap binding protein eIF4E, the ATP-dependent RNA helicase eIF4A and the scaffold protein eIF4G. eIF4G mediates the binding of this mRNA-protein complex to the 43S ribosomal preinitiation complex. There is growing recognition that the components of the translational apparatus interact functionally with cytoskeletal components. Here we report specific effects of the over-expression of human and fission yeast eIF4G domains on cell morphology in Schizosaccharomyces pombe. RESULTS A single gene encoding fission yeast eIF4G was identified and demonstrated to be essential. We have over-expressed fragments corresponding to the conserved functional domains of eIF4G. At expression levels that did not disrupt rates of overall translation or protein accumulation, a fragment of S. pombe eIF4G, 4G-NOB, corresponding to the minimal region of human eIF4G required to support cap-independent mRNA recruitment, was found to impair cell proliferation in fission yeast. This resulted from defects in cytokinesis, and was associated with the disruption of both microtubules and actin microfilaments. The over-expressed fragment was itself localized to the cell ends, the nuclear periphery and the septum. CONCLUSIONS This is the first demonstration of a link between a translation initiation factor and mechanisms controlling cell morphology. The data suggest a direct or indirect interaction between the functional domains of eIF4G and cellular structures involved in cytokinesis.
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Affiliation(s)
- Lida Hashemzadeh-Bonehi
- Biochemistry Laboratory, School of Biological Sciences, University of Sussex, Brighton BN1 9QG, UK
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Valouev IA, Kushnirov VV, Ter-Avanesyan MD. Yeast polypeptide chain release factors eRF1 and eRF3 are involved in cytoskeleton organization and cell cycle regulation. CELL MOTILITY AND THE CYTOSKELETON 2002; 52:161-73. [PMID: 12112144 DOI: 10.1002/cm.10040] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Termination of translation in eukaryotes is controlled by two interacting polypeptide chain release factors, eRF1 and eRF3. eRF1 recognizes nonsense codons UAA, UAG, and UGA, while eRF3 stimulates polypeptide release from the ribosome in a GTP- and eRF1-dependent manner. In the yeast Saccharomyces cerevisiae, eRF1 and eRF3 are encoded by the SUP45 and SUP35 genes, respectively. Here we show that in yeast shortage of any one of the release factors was accompanied by a reduction in the levels of the other release factor and resulted in a substantial increase of nonsense codon readthrough. Besides, repression of the genes encoding these factors caused different effects on cell morphology. Repression of the SUP35 gene caused accumulation of cells of increased size with large buds. This was accompanied by the disappearance of actin cytoskeletal structures, impairment of the mitotic spindle structure, and defects in nuclei division and segregation in mitosis. The evolutionary conserved C-terminal domain of eRF3 similar to the elongation factor EF-1alpha was responsible for these effects. Repression of the SUP45 gene caused accumulation of unbudded cells with 2C and higher DNA content, indicating that DNA replication is uncoupled from budding. The data obtained suggest that eRF1 and eRF3 play additional, nontranslational roles in the yeast cell.
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Affiliation(s)
- Igor A Valouev
- Institute of Experimental Cardiology, Cardiology Research Center, Moscow, Russia
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Gungabissoon RA, Khan S, Hussey PJ, Maciver SK. Interaction of elongation factor 1alpha from Zea mays (ZmEF-1alpha) with F-actin and interplay with the maize actin severing protein, ZmADF3. CELL MOTILITY AND THE CYTOSKELETON 2001; 49:104-11. [PMID: 11443740 DOI: 10.1002/cm.1024] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
EF-1alpha is an abundant eukaryotic protein whose principle function appears to be to bind aminoacyl-tRNA to the ribosome. However, it is also known that EF-1alpha from other sources binds both microtubules and microfilaments. We report the expression of Zea mays EF-1alpha (ZmEF-1alpha) in bacteria and that this protein has similar actin-binding properties as other EF-1alpha members. ZmEF-1alpha bundles actin filaments at low pH (6.5) and inhibits the addition of monomer at both filament ends, possibly as a consequence. ZmEF-1alpha binds actin filaments at all pH values tested (pH 6.0-8.0), indicating that one actin binding site is not pH sensitive. One of the actin-binding sites was determined to reside within domain I (1-223) of ZmEF-1alpha, but this domain did not affect the kinetics of polymerisation. We show that the bundling activity of ZmEF-1alpha is modulated by ZmADF3 a (a Zea mays ADF/cofilin), an actin filament severing protein, in vitro. Bundling of actin filaments caused by ZmEF-1alpha was enhanced in the presence of ZmADF3. The pH-dependent activities of both proteins in vitro suggests that they may work together to respond to temporal and spatial intracellular pH changes to regulate the pattern of the growth of plant cells.
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Affiliation(s)
- R A Gungabissoon
- Genes and Development Group, Department of Biomedical Sciences, University of Edinburgh, Edinburgh, Scotland, United Kingdom
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Munshi R, Kandl KA, Carr-Schmid A, Whitacre JL, Adams AE, Kinzy TG. Overexpression of translation elongation factor 1A affects the organization and function of the actin cytoskeleton in yeast. Genetics 2001; 157:1425-36. [PMID: 11290701 PMCID: PMC1461591 DOI: 10.1093/genetics/157.4.1425] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The translation elongation factor 1 complex (eEF1) plays a central role in protein synthesis, delivering aminoacyl-tRNAs to the elongating ribosome. The eEF1A subunit, a classic G-protein, also performs roles aside from protein synthesis. The overexpression of either eEF1A or eEF1B alpha, the catalytic subunit of the guanine nucleotide exchange factor, in Saccharomyces cerevisiae results in effects on cell growth. Here we demonstrate that overexpression of either factor does not affect the levels of the other subunit or the rate or accuracy of protein synthesis. Instead, the major effects in vivo appear to be at the level of cell morphology and budding. eEF1A overexpression results in dosage-dependent reduced budding and altered actin distribution and cellular morphology. In addition, the effects of excess eEF1A in actin mutant strains show synthetic growth defects, establishing a genetic connection between the two proteins. As the ability of eEF1A to bind and bundle actin is conserved in yeast, these results link the established ability of eEF1A to bind and bundle actin in vitro with nontranslational roles for the protein in vivo.
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Affiliation(s)
- R Munshi
- Department of Molecular Genetics and Microbiology, UMDNJ Robert Wood Johnson Medical School, Piscataway, New Jersey 08854, USA
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Abstract
The experimental evidence accumulated for the last half of the century clearly suggests that inherited variation is not restricted to the changes in genomic sequences. The prion model, originally based on unusual transmission of certain neurodegenerative diseases in mammals, provides a molecular mechanism for the template-like reproduction of alternative protein conformations. Recent data extend this model to protein-based genetic elements in yeast and other fungi. Reproduction and transmission of yeast protein-based genetic elements is controlled by the "prion replication" machinery of the cell, composed of the protein helpers responsible for the processes of assembly and disassembly of protein structures and multiprotein complexes. Among these, the stress-related chaperones of Hsp100 and Hsp70 groups play an important role. Alterations of levels or activity of these proteins result in "mutator" or "antimutator" affects in regard to protein-based genetic elements. "Protein mutagens" have also been identified that affect formation and/or propagation of the alternative protein conformations. Prion-forming abilities appear to be conserved in evolution, despite the divergence of the corresponding amino acid sequences. Moreover, a wide variety of proteins of different origins appear to possess the ability to form amyloid-like aggregates, that in certain conditions might potentially result in prion-like switches. This suggests a possible mechanism for the inheritance of acquired traits, postulated in the Lamarckian theory of evolution. The prion model also puts in doubt the notion that cloned animals are genetically identical to their genome donors, and suggests that genome sequence would not provide a complete information about the genetic makeup of an organism.
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Affiliation(s)
- Y O Chernoff
- School of Biology and Institute for Bioengineering and Bioscience, Georgia Institute of Technology, M/C 0363, 315 Ferst Drive, Atlanta, GA 30332-0363, USA.
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Suda M, Yamada S, Toda T, Miyakawa T, Hirata D. Regulation of Wee1 kinase in response to protein synthesis inhibition. FEBS Lett 2000; 486:305-9. [PMID: 11119724 DOI: 10.1016/s0014-5793(00)02299-7] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
To investigate the mechanism coupling growth (protein synthesis) with cell division, we examined the relationship between the tyrosine kinase Wee1 that inhibits Cdc2-Cdc13 mitosis-inducing kinase by phosphorylating it, and protein synthesis inhibition in fission yeast. The wee1-50 mutant showed supersensitivity to protein synthesis inhibitor, cycloheximide. Wee1 was essential for the G(2) delay upon a partial inhibition of protein synthesis. Indeed, the protein synthesis inhibition caused an increase in the Wee1 protein by the Sty1/Spc1 MAPK-dependent transcriptional and the Sty1/Spc1 MAPK-independent post-transcriptional regulations. Further, the results indicated that the post-transcriptional regulation is important for the G(2) delay.
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Affiliation(s)
- M Suda
- Department of Molecular Biotechnology, Graduate School of Advanced Sciences of Matter, Hiroshima University, Japan
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