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Kim KQ, Nanjaraj Urs AN, Lasehinde V, Greenlaw AC, Hudson BH, Zaher HS. eIF4F complex dynamics are important for the activation of the integrated stress response. Mol Cell 2024; 84:2135-2151.e7. [PMID: 38848692 PMCID: PMC11189614 DOI: 10.1016/j.molcel.2024.04.016] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2023] [Revised: 12/08/2023] [Accepted: 04/19/2024] [Indexed: 06/09/2024]
Abstract
In response to stress, eukaryotes activate the integrated stress response (ISR) via phosphorylation of eIF2α to promote the translation of pro-survival effector genes, such as GCN4 in yeast. Complementing the ISR is the target of rapamycin (TOR) pathway, which regulates eIF4E function. Here, we probe translational control in the absence of eIF4E in Saccharomyces cerevisiae. Intriguingly, we find that loss of eIF4E leads to de-repression of GCN4 translation. In addition, we find that de-repression of GCN4 translation is accompanied by neither eIF2α phosphorylation nor reduction in initiator ternary complex (TC). Our data suggest that when eIF4E levels are depleted, GCN4 translation is de-repressed via a unique mechanism that may involve faster scanning by the small ribosome subunit due to increased local concentration of eIF4A. Overall, our findings suggest that relative levels of eIF4F components are key to ribosome dynamics and may play important roles in translational control of gene expression.
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Affiliation(s)
- Kyusik Q Kim
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA
| | | | - Victor Lasehinde
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Alison C Greenlaw
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Benjamin H Hudson
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA
| | - Hani S Zaher
- Department of Biology, Washington University in St. Louis, St. Louis, MO 63130, USA.
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eIF4E and Interactors from Unicellular Eukaryotes. Int J Mol Sci 2020; 21:ijms21062170. [PMID: 32245232 PMCID: PMC7139794 DOI: 10.3390/ijms21062170] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 03/12/2020] [Accepted: 03/18/2020] [Indexed: 12/22/2022] Open
Abstract
eIF4E, the mRNA cap-binding protein, is well known as a general initiation factor allowing for mRNA-ribosome interaction and cap-dependent translation in eukaryotic cells. In this review we focus on eIF4E and its interactors in unicellular organisms such as yeasts and protozoan eukaryotes. In a first part, we describe eIF4Es from yeast species such as Saccharomyces cerevisiae, Candida albicans, and Schizosaccharomyces pombe. In the second part, we will address eIF4E and interactors from parasite unicellular species—trypanosomatids and marine microorganisms—dinoflagellates. We propose that different strategies have evolved during evolution to accommodate cap-dependent translation to differing requirements. These evolutive “adjustments” involve various forms of eIF4E that are not encountered in all microorganismic species. In yeasts, eIF4E interactors, particularly p20 and Eap1 are found exclusively in Saccharomycotina species such as S. cerevisiae and C. albicans. For protozoan parasites of the Trypanosomatidae family beside a unique cap4-structure located at the 5′UTR of all mRNAs, different eIF4Es and eIF4Gs are active depending on the life cycle stage of the parasite. Additionally, an eIF4E-interacting protein has been identified in Leishmania major which is important for switching from promastigote to amastigote stages. For dinoflagellates, little is known about the structure and function of the multiple and diverse eIF4Es that have been identified thanks to widespread sequencing in recent years.
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Properties of the ternary complex formed by yeast eIF4E, p20 and mRNA. Sci Rep 2018; 8:6707. [PMID: 29712996 PMCID: PMC5928113 DOI: 10.1038/s41598-018-25273-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Accepted: 04/17/2018] [Indexed: 11/25/2022] Open
Abstract
Yeast p20 is a small, acidic protein that binds eIF4E, the cap-binding protein. It has been proposed to affect mRNA translation and degradation, however p20′s function as an eIF4E-binding protein (4E-BP) and its physiological significance has not been clearly established. In this paper we present data demonstrating that p20 is capable of binding directly to mRNA due to electrostatic interaction of a stretch of arginine and histidine residues in the protein with negatively charged phosphates in the mRNA backbone. This interaction contributes to formation of a ternary eIF4E/p20/capped mRNA complex that is more stable than complexes composed of capped mRNA bound to eIF4E in the absence of p20. eIF4E/p20 complex was found to have a more pronounced stimulatory effect on capped mRNA translation than purified eIF4E alone. Addition of peptides containing the eIF4E-binding domains present in p20 (motif YTIDELF), in eIF4G (motif YGPTFLL) or Eap1 (motif YSMNELY) completely inhibited eIF4E-dependent capped mRNA translation (in vitro), but had a greatly reduced inhibitory effect when eIF4E/p20 complex was present. We propose that the eIF4E/p20/mRNA complex serves as a stable depository of mRNAs existing in a dynamic equilibrium with other complexes such as eIF4E/eIF4G (required for translation) and eIF4E/Eap1 (required for mRNA degradation).
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Murata W, Kinpara S, Kitahara N, Yamaguchi Y, Ogita A, Tanaka T, Fujita KI. Cytoskeletal impairment during isoamyl alcohol-induced cell elongation in budding yeast. Sci Rep 2016; 6:31127. [PMID: 27507042 PMCID: PMC4979020 DOI: 10.1038/srep31127] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 07/11/2016] [Indexed: 11/09/2022] Open
Abstract
Isoamyl alcohol (IAA) induces pseudohyphae including cell elongation in the budding yeast Saccharomyces cerevisiae. Detailed regulation of microtubules and actin in developmental transition during cell elongation is poorly understood. Here, we show that although IAA did not affect the intracellular actin level, it reduced the levels of both α- and β-tubulins. In budding yeast, cytoplasmic microtubules are linked to actin via complexes consisting of at least Kar9, Bim1, and Myo2, and reach from the spindle pole body to the cortical attachment site at the bud tip. However, IAA did not affect migration of Myo2 to the bud tip and kept Kar9 in the interior portion of the cell. In addition, bud elongation was observed in Kar9-overexpressing cells in the absence of IAA. These results indicate that impairment of the link between cytoplasmic microtubules and actin is possibly involved in the lowered interaction of Myo2 with Kar9. Our study might explain the reason for delayed cell cycle during IAA-induced cell elongation.
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Affiliation(s)
- Wakae Murata
- Graduate School of Science, Osaka City University, Osaka 558-8585, Japan.,Department of Materials Science, National Institute of Technology, Yonago College, Tottori 683-8502, Japan
| | - Satoko Kinpara
- Graduate School of Science, Osaka City University, Osaka 558-8585, Japan
| | - Nozomi Kitahara
- Graduate School of Science, Osaka City University, Osaka 558-8585, Japan
| | - Yoshihiro Yamaguchi
- Graduate School of Science, Osaka City University, Osaka 558-8585, Japan.,The OCU Advanced Research Institute for Natural Science and Technology, Osaka City University, Osaka 558-8585, Japan
| | - Akira Ogita
- Graduate School of Science, Osaka City University, Osaka 558-8585, Japan.,Research Center for Urban Health and Sports, Osaka City University, Osaka 558-8585, Japan
| | - Toshio Tanaka
- Graduate School of Science, Osaka City University, Osaka 558-8585, Japan
| | - Ken-Ichi Fujita
- Graduate School of Science, Osaka City University, Osaka 558-8585, Japan
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Petrova A, Kiktev D, Askinazi O, Chabelskaya S, Moskalenko S, Zemlyanko O, Zhouravleva G. The translation termination factor eRF1 (Sup45p) of Saccharomyces cerevisiae is required for pseudohyphal growth and invasion. FEMS Yeast Res 2015; 15:fov033. [PMID: 26054854 DOI: 10.1093/femsyr/fov033] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/26/2015] [Indexed: 01/16/2023] Open
Abstract
Mutations in the essential genes SUP45 and SUP35, encoding yeast translation termination factors eRF1 and eRF3, respectively, lead to a wide range of phenotypes and affect various cell processes. In this work, we show that nonsense and missense mutations in the SUP45, but not the SUP35, gene abolish diploid pseudohyphal and haploid invasive growth. Missense mutations that change phosphorylation sites of Sup45 protein do not affect the ability of yeast strains to form pseudohyphae. Deletion of the C-terminal part of eRF1 did not lead to impairment of filamentation. We show a correlation between the filamentation defect and the budding pattern in sup45 strains. Inhibition of translation with specific antibiotics causes a significant reduction in pseudohyphal growth in the wild-type strain, suggesting a strong correlation between translation and the ability for filamentous growth. Partial restoration of pseudohyphal growth by addition of exogenous cAMP assumes that sup45 mutants are defective in the cAMP-dependent pathway that control filament formation.
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Affiliation(s)
- Alexandra Petrova
- Department of Genetics and Biotechnology, St Petersburg State University and St Petersburg Branch Vavilov Institute of General Genetics, Russian Academy of Science, Universitetskaya emb. 7/9, 199034, St Petersburg, Russia
| | - Denis Kiktev
- Department of Genetics and Biotechnology, St Petersburg State University and St Petersburg Branch Vavilov Institute of General Genetics, Russian Academy of Science, Universitetskaya emb. 7/9, 199034, St Petersburg, Russia
| | - Olga Askinazi
- Department of Genetics and Biotechnology, St Petersburg State University and St Petersburg Branch Vavilov Institute of General Genetics, Russian Academy of Science, Universitetskaya emb. 7/9, 199034, St Petersburg, Russia
| | - Svetlana Chabelskaya
- Department of Genetics and Biotechnology, St Petersburg State University and St Petersburg Branch Vavilov Institute of General Genetics, Russian Academy of Science, Universitetskaya emb. 7/9, 199034, St Petersburg, Russia
| | - Svetlana Moskalenko
- Department of Genetics and Biotechnology, St Petersburg State University and St Petersburg Branch Vavilov Institute of General Genetics, Russian Academy of Science, Universitetskaya emb. 7/9, 199034, St Petersburg, Russia
| | - Olga Zemlyanko
- Department of Genetics and Biotechnology, St Petersburg State University and St Petersburg Branch Vavilov Institute of General Genetics, Russian Academy of Science, Universitetskaya emb. 7/9, 199034, St Petersburg, Russia
| | - Galina Zhouravleva
- Department of Genetics and Biotechnology, St Petersburg State University and St Petersburg Branch Vavilov Institute of General Genetics, Russian Academy of Science, Universitetskaya emb. 7/9, 199034, St Petersburg, Russia
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