1
|
Ide NA, Gentry RC, Rudbach MA, Yoo K, Velez PK, Comunale VM, Hartwick EW, Kinz-Thompson CD, Gonzalez RL, Aitken CE. A dynamic compositional equilibrium governs mRNA recognition by eIF3. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.25.581977. [PMID: 38712078 PMCID: PMC11071631 DOI: 10.1101/2024.04.25.581977] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2024]
Abstract
Eukaryotic translation initiation factor (eIF) 3 is a multi-subunit protein complex that binds both ribosomes and messenger RNAs (mRNAs) in order to drive a diverse set of mechanistic steps during translation. Despite its importance, a unifying framework explaining how eIF3 performs these numerous activities is lacking. Using single-molecule light scattering microscopy, we demonstrate that Saccharomyces cerevisiae eIF3 is an equilibrium mixture of the full complex, subcomplexes, and subunits. By extending our microscopy approach to an in vitro reconstituted eIF3 and complementing it with biochemical assays, we define the subspecies comprising this equilibrium and show that, rather than being driven by the full complex, mRNA binding by eIF3 is instead driven by the eIF3a subunit within eIF3a-containing subcomplexes. Our findings provide a mechanistic model for the role of eIF3 in the mRNA recruitment step of translation initiation and establish a mechanistic framework for explaining and investigating the other activities of eIF3.
Collapse
|
2
|
Mormino M, Lenitz I, Siewers V, Nygård Y. Identification of acetic acid sensitive strains through biosensor-based screening of a Saccharomyces cerevisiae CRISPRi library. Microb Cell Fact 2022; 21:214. [PMID: 36243715 PMCID: PMC9571444 DOI: 10.1186/s12934-022-01938-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Accepted: 10/02/2022] [Indexed: 11/10/2022] Open
Abstract
Background Acetic acid tolerance is crucial for the development of robust cell factories for conversion of lignocellulosic hydrolysates that typically contain high levels of acetic acid. Screening mutants for growth in medium with acetic acid is an attractive way to identify sensitive variants and can provide novel insights into the complex mechanisms regulating the acetic acid stress response. Results An acetic acid biosensor based on the Saccharomyces cerevisiae transcription factor Haa1, was used to screen a CRISPRi yeast strain library where dCas9-Mxi was set to individually repress each essential or respiratory growth essential gene. Fluorescence-activated cell sorting led to the enrichment of a population of cells with higher acetic acid retention. These cells with higher biosensor signal were demonstrated to be more sensitive to acetic acid. Biosensor-based screening of the CRISPRi library strains enabled identification of strains with increased acetic acid sensitivity: strains with gRNAs targeting TIF34, MSN5, PAP1, COX10 or TRA1. Conclusions This study demonstrated that biosensors are valuable tools for screening and monitoring acetic acid tolerance in yeast. Fine-tuning the expression of essential genes can lead to altered acetic acid tolerance. Supplementary Information The online version contains supplementary material available at 10.1186/s12934-022-01938-7.
Collapse
Affiliation(s)
- Maurizio Mormino
- Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden
| | - Ibai Lenitz
- Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden
| | - Verena Siewers
- Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden
| | - Yvonne Nygård
- Department of Biology and Biological Engineering, Chalmers University of Technology, Gothenburg, Sweden.
| |
Collapse
|
3
|
Paul EE, Marintchev A. The PCI domains are “winged” HEAT domains. PLoS One 2022; 17:e0268664. [PMID: 36094910 PMCID: PMC9467303 DOI: 10.1371/journal.pone.0268664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2022] [Accepted: 08/17/2022] [Indexed: 11/18/2022] Open
Abstract
The HEAT domains are a family of helical hairpin repeat domains, composed of four or more hairpins. HEAT is derived from the names of four family members: huntingtin, eukaryotic translation elongation factor 3 (eEF3), protein phosphatase 2 regulatory A subunit (PP2A), and mechanistic target of rapamycin (mTOR). HEAT domain-containing proteins play roles in a wide range of cellular processes, such as protein synthesis, nuclear transport and metabolism, and cell signaling. The PCI domains are a related group of helical hairpin domains, with a “winged-helix” (WH) subdomain at their C-terminus, which is responsible for multi-subunit complex formation with other PCI domains. The name is derived from the complexes, where these domains are found: the 26S Proteasome “lid” regulatory subcomplex, the COP9 signalosome (CSN), and eukaryotic translation initiation factor 3 (eIF3). We noted that in structure similarity searches using HEAT domains, sometimes PCI domains appeared in the search results ahead of other HEAT domains, which indicated that the PCI domains could be members of the HEAT domain family, and not a related but separate group, as currently thought. Here, we report extensive structure similarity analysis of HEAT and PCI domains, both within and between the two groups of proteins. We present evidence that the PCI domains as a group have greater structural similarity with individual groups of HEAT domains than some of the HEAT domain groups have among each other. Therefore, our results indicate that the PCI domains have evolved from a HEAT domain that acquired a WH subdomain. The WH subdomain in turn mediated self-association into a multi-subunit complex, which eventually evolved into the common ancestor of the Proteasome lid/CSN/eIF3.
Collapse
Affiliation(s)
- Eleanor Elise Paul
- Department of Physiology & Biophysics, Boston University School of Medicine, Boston, Massachusetts, United States of America
| | - Assen Marintchev
- Department of Physiology & Biophysics, Boston University School of Medicine, Boston, Massachusetts, United States of America
- * E-mail:
| |
Collapse
|
4
|
Reprogramming mRNA Expression in Response to Defect in RNA Polymerase III Assembly in the Yeast Saccharomyces cerevisiae. Int J Mol Sci 2021; 22:ijms22147298. [PMID: 34298922 PMCID: PMC8306304 DOI: 10.3390/ijms22147298] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 06/25/2021] [Accepted: 07/03/2021] [Indexed: 12/18/2022] Open
Abstract
The coordinated transcription of the genome is the fundamental mechanism in molecular biology. Transcription in eukaryotes is carried out by three main RNA polymerases: Pol I, II, and III. One basic problem is how a decrease in tRNA levels, by downregulating Pol III efficiency, influences the expression pattern of protein-coding genes. The purpose of this study was to determine the mRNA levels in the yeast mutant rpc128-1007 and its overdose suppressors, RBS1 and PRT1. The rpc128-1007 mutant prevents assembly of the Pol III complex and functionally mimics similar mutations in human Pol III, which cause hypomyelinating leukodystrophies. We applied RNAseq followed by the hierarchical clustering of our complete RNA-seq transcriptome and functional analysis of genes from the clusters. mRNA upregulation in rpc128-1007 cells was generally stronger than downregulation. The observed induction of mRNA expression was mostly indirect and resulted from the derepression of general transcription factor Gcn4, differently modulated by suppressor genes. rpc128-1007 mutation, regardless of the presence of suppressors, also resulted in a weak increase in the expression of ribosome biogenesis genes. mRNA genes that were downregulated by the reduction of Pol III assembly comprise the proteasome complex. In summary, our results provide the regulatory links affected by Pol III assembly that contribute differently to cellular fitness.
Collapse
|
5
|
Malcova I, Senohrabkova L, Novakova L, Hasek J. eIF3a Destabilization and TDP-43 Alter Dynamics of Heat-Induced Stress Granules. Int J Mol Sci 2021; 22:ijms22105164. [PMID: 34068231 PMCID: PMC8153170 DOI: 10.3390/ijms22105164] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2021] [Revised: 05/04/2021] [Accepted: 05/08/2021] [Indexed: 12/17/2022] Open
Abstract
Stress granules (SGs) are membrane-less assemblies arising upon various stresses in eukaryotic cells. They sequester mRNAs and proteins from stressful conditions and modulate gene expression to enable cells to resume translation and growth after stress relief. SGs containing the translation initiation factor eIF3a/Rpg1 arise in yeast cells upon robust heat shock (HS) at 46 °C only. We demonstrate that the destabilization of Rpg1 within the PCI domain in the Rpg1-3 variant leads to SGs assembly already at moderate HS at 42 °C. These are bona fide SGs arising upon translation arrest containing mRNAs, which are components of the translation machinery, and associating with P-bodies. HS SGs associate with endoplasmatic reticulum and mitochondria and their contact sites ERMES. Although Rpg1-3-labeled SGs arise at a lower temperature, their disassembly is delayed after HS at 46 °C. Remarkably, the delayed disassembly of HS SGs after the robust HS is reversed by TDP-43, which is a human protein connected with amyotrophic lateral sclerosis. TDP-43 colocalizes with HS SGs in yeast cells and facilitates cell regrowth after the stress relief. Based on our results, we propose yeast HS SGs labeled by Rpg1 and its variants as a novel model system to study functions of TDP-43 in stress granules disassembly.
Collapse
Affiliation(s)
- Ivana Malcova
- Institute of Microbiology, Czech Academy of Sciences, Videnska 1083, 14220 Prague, Czech Republic; (L.S.); (L.N.); (J.H.)
- Correspondence: ; Tel.: +420-241062769
| | - Lenka Senohrabkova
- Institute of Microbiology, Czech Academy of Sciences, Videnska 1083, 14220 Prague, Czech Republic; (L.S.); (L.N.); (J.H.)
- First Faculty of Medicine, Charles University, Katerinska 42, 12108 Prague, Czech Republic
| | - Lenka Novakova
- Institute of Microbiology, Czech Academy of Sciences, Videnska 1083, 14220 Prague, Czech Republic; (L.S.); (L.N.); (J.H.)
| | - Jiri Hasek
- Institute of Microbiology, Czech Academy of Sciences, Videnska 1083, 14220 Prague, Czech Republic; (L.S.); (L.N.); (J.H.)
| |
Collapse
|
6
|
Ma S, Dong Z, Cui Q, Liu JY, Zhang JT. eIF3i regulation of protein synthesis, cell proliferation, cell cycle progression, and tumorigenesis. Cancer Lett 2020; 500:11-20. [PMID: 33301799 DOI: 10.1016/j.canlet.2020.12.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 11/22/2020] [Accepted: 12/06/2020] [Indexed: 02/07/2023]
Abstract
eIF3i, a 36-kDa protein, is a putative subunit of the eIF3 complex important for translation initiation of mRNAs. It is a WD40 domain-containing protein with seven WD40 repeats that forms a β-propeller structure with an important function in pre-initiation complex formation and mRNA translation initiation. In addition to participating in the eIF3 complex formation for global translational control, eIF3i may bind to specific mRNAs and regulate their translation individually. Furthermore, eIF3i has been shown to bind to TGF-β type II receptor and participate in TGF-β signaling. It may also participate in and regulate other signaling pathways including Wnt/β-catenin pathway via translational regulation of COX-2 synthesis. These multiple canonical and noncanonical functions of eIF3i in translational control and in regulating signal transduction pathways may be responsible for its role in cell differentiation, cell cycle regulation, proliferation, and tumorigenesis. In this review, we will critically evaluate recent progresses and assess future prospects in studying eIF3i.
Collapse
Affiliation(s)
- Shijie Ma
- Affiliated Cancer Hospital & Institute of Guangzhou Medical University, Guangzhou, Guangdong, 510095, China.
| | - Zizheng Dong
- Department of Cancer Biology, University of Toledo College of Medicine and Life Sciences, Toledo, OH, 43614, USA
| | - Qingbin Cui
- Department of Cancer Biology, University of Toledo College of Medicine and Life Sciences, Toledo, OH, 43614, USA
| | - Jing-Yuan Liu
- Department of Medicine, University of Toledo College of Medicine and Life Sciences, Toledo, OH, 43614, USA.
| | - Jian-Ting Zhang
- Department of Cancer Biology, University of Toledo College of Medicine and Life Sciences, Toledo, OH, 43614, USA.
| |
Collapse
|
7
|
Nocua PA, Requena JM, Puerta CJ. Identification of the interactomes associated with SCD6 and RBP42 proteins in Leishmania braziliensis. J Proteomics 2020; 233:104066. [PMID: 33296709 DOI: 10.1016/j.jprot.2020.104066] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 11/16/2020] [Accepted: 11/29/2020] [Indexed: 02/04/2023]
Abstract
Leishmania are protozoan parasites responsible for leishmaniasis. These parasites present a precise gene regulation that allows them to survive different environmental conditions during their digenetic life cycle. This adaptation depends on the regulation of the expression of a wide variety of genes, which occurs, mainly at the post-transcriptional level. This differential gene expression is achieved by mechanisms based mainly in RNA binding proteins that regulate the translation and/or stability of mRNA targets by interaction with cis elements principally located in the untranslated regions (UTR). In recent studies, our group identified and characterized two proteins, SCD6 and RBP42, as RNA binding proteins in Leishmania braziliensis. To find clues about the cellular processes in which these proteins are involved, this work was aimed to determine the SCD6- and RBP42-interacting proteins (interactome) in L. braziliensis promastigotes. For this purpose, after an in vivo UV cross-linking, cellular extracts were used to immunoprecipitated, by specific antibodies, protein complexes in which SCD6 or RBP42 were present. Protein mass spectrometry analysis of the immunoprecipitated proteins identified 96 proteins presumably associated with SCD6 and 173 proteins associated with RBP42. Notably, a significant proportion of the identified proteins were shared in both interactomes, indicating a possible functional relationship between SCD6 and RBP42. Remarkably, many of the proteins identified in the SCD6 and RBP42 interactomes are related to RNA metabolism and translation processes, and many of them have been described as components of ribonucleoprotein (RNP) granules in Leishmania and related trypanosomatids. Thus, these results support a role of SCD6 and RBP42 in the assembly and/or function of mRNA-protein complexes, participating in the fate (decay/accumulation/translation) of L. braziliensis transcripts. SIGNIFICANCE: Parasites of the Leishmania genus present a particular regulation of gene expression, operating mainly at the post-transcriptional level, surely aimed to modulate quickly both mRNA and protein levels to survive the sudden environmental changes that occur during a parasite's life cycle as it moves from one host to another. This regulation of gene expression processes would be governed by the interaction of mRNA with RNA binding proteins. Nevertheless, the entirety of protein networks involved in these regulatory processes is far from being understood. In this regard, our work is contributing to stablish protein networks in which the L. braziliensis SCD6 and RBP42 proteins are involved; these proteins, in previous works, have been described as RNA binding proteins and found to participate in gene regulation in different cells and organisms. Additionally, our data point out a possible functional relationship between SCD6 and RBP42 proteins as constituents of mRNA granules, like processing bodies or stress granules, which are essential structures in the regulation of gene expression. This knowledge could provide a new approach for the development of therapeutic targets to control Leishmania infections.
Collapse
Affiliation(s)
- Paola A Nocua
- Laboratorio de Parasitología Molecular, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá, Colombia; Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Universidad Autónoma de Madrid, Madrid, Spain.
| | - José M Requena
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Universidad Autónoma de Madrid, Madrid, Spain.
| | - Concepción J Puerta
- Laboratorio de Parasitología Molecular, Facultad de Ciencias, Pontificia Universidad Javeriana, Bogotá, Colombia.
| |
Collapse
|
8
|
Structural Differences in Translation Initiation between Pathogenic Trypanosomatids and Their Mammalian Hosts. Cell Rep 2020; 33:108534. [PMID: 33357443 PMCID: PMC7773551 DOI: 10.1016/j.celrep.2020.108534] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 10/08/2020] [Accepted: 11/25/2020] [Indexed: 11/25/2022] Open
Abstract
Canonical mRNA translation in eukaryotes begins with the formation of the 43S pre-initiation complex (PIC). Its assembly requires binding of initiator Met-tRNAiMet and several eukaryotic initiation factors (eIFs) to the small ribosomal subunit (40S). Compared to their mammalian hosts, trypanosomatids present significant structural differences in their 40S, suggesting substantial variability in translation initiation. Here, we determine the structure of the 43S PIC from Trypanosoma cruzi, the parasite causing Chagas disease. Our structure shows numerous specific features, such as the variant eIF3 structure and its unique interactions with the large rRNA expansion segments (ESs) 9S, 7S, and 6S, and the association of a kinetoplastid-specific DDX60-like helicase. It also reveals the 40S-binding site of the eIF5 C-terminal domain and structures of key terminal tails of several conserved eIFs underlying their activities within the PIC. Our results are corroborated by glutathione S-transferase (GST) pull-down assays in both human and T. cruzi and mass spectrometry data. Structure of the 43S pre-initiation complex from Trypanosoma cruzi is solved at 3.33 Å The kinetoplastids’ eIF3 core is a septamer that binds mainly the unique, extended ES7s A kinetoplastid-specific DDX60-like helicase binds to the 43S PIC entry pore The 40S positions of eIF5-CTD and key tails of several eIFs are determined
Collapse
|
9
|
DENR promotes translation reinitiation via ribosome recycling to drive expression of oncogenes including ATF4. Nat Commun 2020; 11:4676. [PMID: 32938922 PMCID: PMC7494916 DOI: 10.1038/s41467-020-18452-2] [Citation(s) in RCA: 46] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Accepted: 08/14/2020] [Indexed: 12/19/2022] Open
Abstract
Translation efficiency varies considerably between different mRNAs, thereby impacting protein expression. Translation of the stress response master-regulator ATF4 increases upon stress, but the molecular mechanisms are not well understood. We discover here that translation factors DENR, MCTS1 and eIF2D are required to induce ATF4 translation upon stress by promoting translation reinitiation in the ATF4 5'UTR. We find DENR and MCTS1 are only needed for reinitiation after upstream Open Reading Frames (uORFs) containing certain penultimate codons, perhaps because DENR•MCTS1 are needed to evict only certain tRNAs from post-termination 40S ribosomes. This provides a model for how DENR and MCTS1 promote translation reinitiation. Cancer cells, which are exposed to many stresses, require ATF4 for survival and proliferation. We find a strong correlation between DENR•MCTS1 expression and ATF4 activity across cancers. Furthermore, additional oncogenes including a-Raf, c-Raf and Cdk4 have long uORFs and are translated in a DENR•MCTS1 dependent manner.
Collapse
|
10
|
Wagner S, Herrmannová A, Hronová V, Gunišová S, Sen ND, Hannan RD, Hinnebusch AG, Shirokikh NE, Preiss T, Valášek LS. Selective Translation Complex Profiling Reveals Staged Initiation and Co-translational Assembly of Initiation Factor Complexes. Mol Cell 2020; 79:546-560.e7. [PMID: 32589964 PMCID: PMC7447980 DOI: 10.1016/j.molcel.2020.06.004] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Revised: 04/10/2020] [Accepted: 05/18/2020] [Indexed: 11/25/2022]
Abstract
Translational control targeting the initiation phase is central to the regulation of gene expression. Understanding all of its aspects requires substantial technological advancements. Here we modified yeast translation complex profile sequencing (TCP-seq), related to ribosome profiling, and adapted it for mammalian cells. Human TCP-seq, capable of capturing footprints of 40S subunits (40Ss) in addition to 80S ribosomes (80Ss), revealed that mammalian and yeast 40Ss distribute similarly across 5'TRs, indicating considerable evolutionary conservation. We further developed yeast and human selective TCP-seq (Sel-TCP-seq), enabling selection of 40Ss and 80Ss associated with immuno-targeted factors. Sel-TCP-seq demonstrated that eIF2 and eIF3 travel along 5' UTRs with scanning 40Ss to successively dissociate upon AUG recognition; notably, a proportion of eIF3 lingers on during the initial elongation cycles. Highlighting Sel-TCP-seq versatility, we also identified four initiating 48S conformational intermediates, provided novel insights into ATF4 and GCN4 mRNA translational control, and demonstrated co-translational assembly of initiation factor complexes.
Collapse
Affiliation(s)
- Susan Wagner
- EMBL-Australia Collaborating Group, Department of Genome Sciences, John Curtin School of Medical Research, Australian National University, Canberra, ACT 2601, Australia; Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20, Prague, Czech Republic.
| | - Anna Herrmannová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20, Prague, Czech Republic
| | - Vladislava Hronová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20, Prague, Czech Republic
| | - Stanislava Gunišová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20, Prague, Czech Republic
| | - Neelam D Sen
- Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Ross D Hannan
- Australian Cancer Research Foundation Department of Cancer Biology and Therapeutics, John Curtin School of Medical Research, Australian National University, Canberra, ACT 2601, Australia
| | - Alan G Hinnebusch
- Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Nikolay E Shirokikh
- EMBL-Australia Collaborating Group, Department of Genome Sciences, John Curtin School of Medical Research, Australian National University, Canberra, ACT 2601, Australia
| | - Thomas Preiss
- EMBL-Australia Collaborating Group, Department of Genome Sciences, John Curtin School of Medical Research, Australian National University, Canberra, ACT 2601, Australia; Victor Chang Cardiac Research Institute, Darlinghurst, NSW 2010, Australia.
| | - Leoš Shivaya Valášek
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Videnska 1083, 142 20, Prague, Czech Republic.
| |
Collapse
|
11
|
Bohlen J, Fenzl K, Kramer G, Bukau B, Teleman AA. Selective 40S Footprinting Reveals Cap-Tethered Ribosome Scanning in Human Cells. Mol Cell 2020; 79:561-574.e5. [DOI: 10.1016/j.molcel.2020.06.005] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2019] [Revised: 04/10/2020] [Accepted: 05/18/2020] [Indexed: 11/27/2022]
|
12
|
Zhang C, Cui T, Zhang F, Xue Z, Miao J, Wang W, Liu X. Identification of differentially activated pathways in Phytophthora sojae at the mycelial, cyst, and oospore stages by TMT-based quantitative proteomics analysis. J Proteomics 2020; 221:103776. [PMID: 32268220 DOI: 10.1016/j.jprot.2020.103776] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 03/25/2020] [Accepted: 04/02/2020] [Indexed: 01/24/2023]
Abstract
Phytophthora sojae is a widely distributed, destructive oomycete plant pathogen that has been developed as a model for oomycete biology. Given the important but limited reports on the comparison of the sexual and asexual stages in Phytophthora, we performed a large-scale quantitative proteomics study on two key asexual life stages of P. sojae-the mycelium and cyst-as well as on the oospore, which is a key sexual stage. Over 29,631 peptides from 4688 proteins were analyzed. Briefly, 445 proteins, 624 proteins, and 579 proteins were defined as differentially quantified proteins in cyst vs mycelium, oospore vs cyst, and oospore vs mycelium comparisons, respectively (|log2 fold change| > 1 and P < 0.05). Compared to the mycelium and oospore, fatty acid and nitrogen metabolism were specifically induced in cysts. In oospores, the up-regulated proteins focused on RNA transport and protein processing in endoplasmic reticulum, indicating translation, folding, and the secretion of core cellular or stage-specific proteins active in oospores, which might be used for oospore germination. The data presented expand our knowledge of pathways specifically linked to asexual and sexual stages of this pathogen. BIOLOGICAL SIGNIFICANCE: The sexual spores (oospores) in oomycetes have thick cell walls and can survive in the soil for years, thus providing a primary source and allowing the reinfection of their host plant in subsequent growing seasons. However, the proteomic study on oospores remains very limited as they are generally considered to be dormant. In the present study, we successfully isolated oospores, and performed a large-scale comparative quantitative proteomics study on this key sexual stage and two representative asexual stages of P. sojae. The results provide an improved understanding of P. sojae biology and suggest potential metabolic targets for disease control at the three different developmental stages in oomycetes.
Collapse
Affiliation(s)
- Can Zhang
- Department of Plant Pathology, China Agricultural University, Beijing 100193, China
| | - Tongshan Cui
- Department of Plant Pathology, China Agricultural University, Beijing 100193, China
| | - Fan Zhang
- Department of Plant Pathology, China Agricultural University, Beijing 100193, China
| | - Zhaolin Xue
- Department of Plant Pathology, China Agricultural University, Beijing 100193, China
| | - Jianqiang Miao
- State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Yangling 712100, China
| | - Weizhen Wang
- Department of Plant Pathology, China Agricultural University, Beijing 100193, China
| | - Xili Liu
- State Key Laboratory of Crop Stress Biology for Arid Areas, Northwest A&F University, Yangling 712100, China.
| |
Collapse
|
13
|
Zeman J, Itoh Y, Kukačka Z, Rosůlek M, Kavan D, Kouba T, Jansen ME, Mohammad MP, Novák P, Valášek LS. Binding of eIF3 in complex with eIF5 and eIF1 to the 40S ribosomal subunit is accompanied by dramatic structural changes. Nucleic Acids Res 2019; 47:8282-8300. [PMID: 31291455 PMCID: PMC6735954 DOI: 10.1093/nar/gkz570] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Revised: 06/12/2019] [Accepted: 07/05/2019] [Indexed: 12/31/2022] Open
Abstract
eIF3 is a large multiprotein complex serving as an essential scaffold promoting binding of other eIFs to the 40S subunit, where it coordinates their actions during translation initiation. Perhaps due to a high degree of flexibility of multiple eIF3 subunits, a high-resolution structure of free eIF3 from any organism has never been solved. Employing genetics and biochemistry, we previously built a 2D interaction map of all five yeast eIF3 subunits. Here we further improved the previously reported in vitro reconstitution protocol of yeast eIF3, which we cross-linked and trypsin-digested to determine its overall shape in 3D by advanced mass-spectrometry. The obtained cross-links support our 2D subunit interaction map and reveal that eIF3 is tightly packed with its WD40 and RRM domains exposed. This contrasts with reported cryo-EM structures depicting eIF3 as a molecular embracer of the 40S subunit. Since the binding of eIF1 and eIF5 further fortified the compact architecture of eIF3, we suggest that its initial contact with the 40S solvent-exposed side makes eIF3 to open up and wrap around the 40S head with its extended arms. In addition, we mapped the position of eIF5 to the region below the P- and E-sites of the 40S subunit.
Collapse
Affiliation(s)
- Jakub Zeman
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, The Czech Republic
| | - Yuzuru Itoh
- Institute of Genetics and Molecular and Cellular Biology, CNRS UMR7104, INSERM UMR964, Illkirch, France
| | - Zdeněk Kukačka
- Laboratory of Structural Biology and Cell Signaling, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, The Czech Republic
| | - Michal Rosůlek
- Laboratory of Structural Biology and Cell Signaling, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, The Czech Republic
| | - Daniel Kavan
- Laboratory of Structural Biology and Cell Signaling, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, The Czech Republic
| | - Tomáš Kouba
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, The Czech Republic
| | - Myrte E Jansen
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, The Czech Republic
| | - Mahabub P Mohammad
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, The Czech Republic
| | - Petr Novák
- Laboratory of Structural Biology and Cell Signaling, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, The Czech Republic
| | - Leoš S Valášek
- Laboratory of Regulation of Gene Expression, Institute of Microbiology of the Czech Academy of Sciences, Prague, Videnska 1083, 142 20, The Czech Republic
| |
Collapse
|
14
|
Raabe K, Honys D, Michailidis C. The role of eukaryotic initiation factor 3 in plant translation regulation. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2019; 145:75-83. [PMID: 31665669 DOI: 10.1016/j.plaphy.2019.10.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2019] [Revised: 10/07/2019] [Accepted: 10/14/2019] [Indexed: 06/10/2023]
Abstract
Regulation of translation represents a critical step in the regulation of gene expression. In plants, the translation regulation plays an important role at all stages of development and, during stress responses, functions as a fast and flexible tool which not only modulates the global translation rate but also controls the production of specific proteins. Regulation of translation is mostly focused on the initiation phase. There, one of essential initiation factors is the large multisubunit protein complex of eukaryotic translation initiation factor 3 (eIF3). In all eukaryotes, the general eIF3 function is to scaffold the formation of the translation initiation complex and to enhance the accuracy of scanning mechanism for start codon selection. Over the past decades, additional eIF3 functions were described as necessary for development in various eukaryotic organisms, including plants. The importance of the eIF3 complex lies not only at the global level of initiation event, but also in the precise translation regulation of specific transcripts. This review gathers the available information on functions of the plant eIF3 complex.
Collapse
Affiliation(s)
- Karel Raabe
- Institute of Experimental Botany, The Czech Academy of Sciences, Rozvojová 263, 165 02, Praha 6, Czech Republic
| | - David Honys
- Institute of Experimental Botany, The Czech Academy of Sciences, Rozvojová 263, 165 02, Praha 6, Czech Republic
| | - Christos Michailidis
- Institute of Experimental Botany, The Czech Academy of Sciences, Rozvojová 263, 165 02, Praha 6, Czech Republic.
| |
Collapse
|
15
|
Eliseev B, Yeramala L, Leitner A, Karuppasamy M, Raimondeau E, Huard K, Alkalaeva E, Aebersold R, Schaffitzel C. Structure of a human cap-dependent 48S translation pre-initiation complex. Nucleic Acids Res 2019; 46:2678-2689. [PMID: 29401259 PMCID: PMC5861459 DOI: 10.1093/nar/gky054] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Accepted: 01/21/2018] [Indexed: 01/13/2023] Open
Abstract
Eukaryotic translation initiation is tightly regulated, requiring a set of conserved initiation factors (eIFs). Translation of a capped mRNA depends on the trimeric eIF4F complex and eIF4B to load the mRNA onto the 43S pre-initiation complex comprising 40S and initiation factors 1, 1A, 2, 3 and 5 as well as initiator-tRNA. Binding of the mRNA is followed by mRNA scanning in the 48S pre-initiation complex, until a start codon is recognised. Here, we use a reconstituted system to prepare human 48S complexes assembled on capped mRNA in the presence of eIF4B and eIF4F. The highly purified h-48S complexes are used for cross-linking/mass spectrometry, revealing the protein interaction network in this complex. We report the electron cryo-microscopy structure of the h-48S complex at 6.3 Å resolution. While the majority of eIF4B and eIF4F appear to be flexible with respect to the ribosome, additional density is detected at the entrance of the 40S mRNA channel which we attribute to the RNA-recognition motif of eIF4B. The eight core subunits of eIF3 are bound at the 40S solvent-exposed side, as well as the subunits eIF3d, eIF3b and eIF3i. elF2 and initiator-tRNA bound to the start codon are present at the 40S intersubunit side. This cryo-EM structure represents a molecular snap-shot revealing the h-48S complex following start codon recognition.
Collapse
Affiliation(s)
- Boris Eliseev
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France
| | - Lahari Yeramala
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France
| | - Alexander Leitner
- ETH Zürich, Institute of Molecular Systems Biology, Auguste-Piccard-Hof 1, 8093 Zürich, Switzerland
| | - Manikandan Karuppasamy
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France
| | - Etienne Raimondeau
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France
| | - Karine Huard
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France
| | - Elena Alkalaeva
- Engelhardt Institute of Molecular Biology, the Russian Academy of Sciences, 119991 Moscow, Russia
| | - Ruedi Aebersold
- ETH Zürich, Institute of Molecular Systems Biology, Auguste-Piccard-Hof 1, 8093 Zürich, Switzerland.,Faculty of Science, University of Zürich, 8057 Zürich, Switzerland
| | - Christiane Schaffitzel
- European Molecular Biology Laboratory, Grenoble Outstation, 71 Avenue des Martyrs, 38042 Grenoble, France.,School of Biochemistry, University of Bristol, Bristol BS8 1TD, UK
| |
Collapse
|
16
|
Liu X, Schuessler PJ, Sahoo A, Walker SE. Reconstitution and analyses of RNA interactions with eukaryotic translation initiation factors and ribosomal preinitiation complexes. Methods 2019; 162-163:42-53. [PMID: 30926531 DOI: 10.1016/j.ymeth.2019.03.024] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2019] [Revised: 03/22/2019] [Accepted: 03/23/2019] [Indexed: 11/25/2022] Open
Abstract
Control of translation initiation plays a critical role in the regulation of gene expression in all organisms, yet the mechanics of translation initiation in eukaryotic organisms are not well understood. Confounding studies of translation are the large number and overlapping functions of many initiation factors in cells, and a lack of cap-dependence in many in vitro systems. To shed light on intricate mechanisms that are often obscured in vivo, we use a fully reconstituted translation initiation system for analyzing RNA interactions with eukaryotic translation initiation factors and complexes from the model organism Saccharomyces cerevisiae. This system exhibits strong cap dependence, and dependence on translation factors varies with mRNA 5' UTR sequences as expected from genome-wide studies of translation. Here we provide optimized protocols for purification and analysis of the effects of labeled and unlabeled mRNA recruitment factors on both the rate and factor dependence of mRNA recruitment to the translation preinitiation complex in response to RNA sequence- and structure-changes. In addition to providing streamlined and detailed protocols, we describe a new construct for purification of higher yields of fluorescently labeled and unlabeled full-length eIF4G.
Collapse
Affiliation(s)
- Xiaozhuo Liu
- Department of Biological Sciences, The State University of New York at Buffalo, 109 Cooke Hall, Buffalo, NY 14260, United States
| | - Peter J Schuessler
- Department of Biological Sciences, The State University of New York at Buffalo, 109 Cooke Hall, Buffalo, NY 14260, United States
| | - Ansuman Sahoo
- Department of Biological Sciences, The State University of New York at Buffalo, 109 Cooke Hall, Buffalo, NY 14260, United States
| | - Sarah E Walker
- Department of Biological Sciences, The State University of New York at Buffalo, 109 Cooke Hall, Buffalo, NY 14260, United States.
| |
Collapse
|
17
|
Senohrabkova L, Malcova I, Hasek J. An aggregation-prone mutant of eIF3a forms reversible assemblies escaping spatial control in exponentially growing yeast cells. Curr Genet 2019; 65:919-940. [PMID: 30715564 DOI: 10.1007/s00294-019-00940-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 01/14/2019] [Accepted: 01/17/2019] [Indexed: 10/27/2022]
Abstract
Cells have elaborated a complex strategy to maintain protein homeostasis under physiological as well as stress conditions with the aim to ensure the smooth functioning of vital processes and producing healthy offspring. Impairment of one of the most important processes in living cells, translation, might have serious consequences including various brain disorders in humans. Here, we describe a variant of the translation initiation factor eIF3a, Rpg1-3, mutated in its PCI domain that displays an attenuated translation efficiency and formation of reversible assemblies at physiological growth conditions. Rpg1-3-GFP assemblies are not sequestered within mother cells only as usual for misfolded-protein aggregates and are freely transmitted from the mother cell into the bud although they are of non-amyloid nature. Their bud-directed transmission and the active movement within the cell area depend on the intact actin cytoskeleton and the related molecular motor Myo2. Mutations in the Rpg1-3 protein render not only eIF3a but, more importantly, also the eIF3 core complex prone to aggregation that is potentiated by the limited availability of Hsp70 and Hsp40 chaperones. Our results open the way to understand mechanisms yeast cells employ to cope with malfunction and aggregation of essential proteins and their complexes.
Collapse
Affiliation(s)
- Lenka Senohrabkova
- Laboratory of Cell Reproduction, Institute of Microbiology of the CAS, Videnska 1083, 14220, Prague 4, Czech Republic
- First Faculty of Medicine, Charles University, Katerinska 42, 12108, Prague 2, Czech Republic
| | - Ivana Malcova
- Laboratory of Cell Reproduction, Institute of Microbiology of the CAS, Videnska 1083, 14220, Prague 4, Czech Republic.
| | - Jiri Hasek
- Laboratory of Cell Reproduction, Institute of Microbiology of the CAS, Videnska 1083, 14220, Prague 4, Czech Republic.
| |
Collapse
|
18
|
James CC, Smyth JW. Alternative mechanisms of translation initiation: An emerging dynamic regulator of the proteome in health and disease. Life Sci 2018; 212:138-144. [PMID: 30290184 DOI: 10.1016/j.lfs.2018.09.054] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2018] [Revised: 09/18/2018] [Accepted: 09/27/2018] [Indexed: 01/06/2023]
Abstract
Eukaryotic mRNAs were historically thought to rely exclusively on recognition and binding of their 5' cap by initiation factors to effect protein translation. While internal ribosome entry sites (IRESs) are well accepted as necessary for the cap-independent translation of many viral genomes, there is now recognition that eukaryotic mRNAs also undergo non-canonical modes of translation initiation. Recently, high-throughput assays have identified thousands of mammalian transcripts with translation initiation occurring at non-canonical start codons, upstream of and within protein coding regions. In addition to IRES-mediated events, regulatory mechanisms of translation initiation have been described involving alternate 5' cap recognition, mRNA sequence elements, and ribosome selection. These mechanisms ensure translation of specific mRNAs under conditions where cap-dependent translation is shut down and contribute to pathological states including cardiac hypertrophy and cancer. Such global and gene-specific dynamic regulation of translation presents us with an increasing number of novel therapeutic targets. While these newly discovered modes of translation initiation have been largely studied in isolation, it is likely that several act on the same mRNA and exquisite coordination is necessary to maintain 'normal' translation. In this short review, we summarize the current state of knowledge of these alternative mechanisms of eukaryotic protein translation, their contribution to normal and pathological cell biology, and the potential of targeting translation initiation therapeutically in human disease.
Collapse
Affiliation(s)
- Carissa C James
- Virginia Tech Carilion Research Institute and School of Medicine, Roanoke, VA, USA; Graduate Program in Translational Biology, Medicine, and Health, Virginia Tech, Blacksburg, VA, USA; Center for Heart and Regenerative Medicine, Virginia Tech Carilion Research Institute, Roanoke, VA, USA
| | - James W Smyth
- Virginia Tech Carilion Research Institute and School of Medicine, Roanoke, VA, USA; Department of Biological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA, USA; Center for Heart and Regenerative Medicine, Virginia Tech Carilion Research Institute, Roanoke, VA, USA.
| |
Collapse
|
19
|
Feng X, Li J, Liu P. The Biological Roles of Translation Initiation Factor 3b. Int J Biol Sci 2018; 14:1630-1635. [PMID: 30416377 PMCID: PMC6216031 DOI: 10.7150/ijbs.26932] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Accepted: 08/05/2018] [Indexed: 11/12/2022] Open
Abstract
Translation has important roles in almost all physiological and pathological processes, and translation initiation factors are particularly relevant to the translation initiation step, which is the most important step in translation regulation. Translation initiation factor 3b (eIF3b), a key subunit of the largest translation initiation factor 3 (eIF3), is widely considered a scaffold protein that acts to ensure the accuracy of translation initiation. A series of recent finds has revealed that eIF3 is closely related to oncogenesis. However, the concrete mechanism by which eIF3b is involve in carcinogenesis remains elusive. Here, we summarize a series of research findings regarding the relationship between eIF3b, translation and cancer.
Collapse
Affiliation(s)
- Xuefei Feng
- Center for Translational Medicine, the First Affiliated Hospital of Xi'an Jiaotong University.,Key Laboratory for Tumor Precision Medicine of Shaanxi Province, the First Affiliated Hospital of Xi'an Jiaotong University
| | - Juan Li
- Center for Translational Medicine, the First Affiliated Hospital of Xi'an Jiaotong University.,Key Laboratory for Tumor Precision Medicine of Shaanxi Province, the First Affiliated Hospital of Xi'an Jiaotong University
| | - Peijun Liu
- Center for Translational Medicine, the First Affiliated Hospital of Xi'an Jiaotong University.,Key Laboratory for Tumor Precision Medicine of Shaanxi Province, the First Affiliated Hospital of Xi'an Jiaotong University
| |
Collapse
|
20
|
Shirokikh NE, Preiss T. Translation initiation by cap-dependent ribosome recruitment: Recent insights and open questions. WILEY INTERDISCIPLINARY REVIEWS-RNA 2018; 9:e1473. [PMID: 29624880 DOI: 10.1002/wrna.1473] [Citation(s) in RCA: 91] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Revised: 02/02/2018] [Accepted: 02/14/2018] [Indexed: 12/14/2022]
Abstract
Gene expression universally relies on protein synthesis, where ribosomes recognize and decode the messenger RNA template by cycling through translation initiation, elongation, and termination phases. All aspects of translation have been studied for decades using the tools of biochemistry and molecular biology available at the time. Here, we focus on the mechanism of translation initiation in eukaryotes, which is remarkably more complex than prokaryotic initiation and is the target of multiple types of regulatory intervention. The "consensus" model, featuring cap-dependent ribosome entry and scanning of mRNA leader sequences, represents the predominantly utilized initiation pathway across eukaryotes, although several variations of the model and alternative initiation mechanisms are also known. Recent advances in structural biology techniques have enabled remarkable molecular-level insights into the functional states of eukaryotic ribosomes, including a range of ribosomal complexes with different combinations of translation initiation factors that are thought to represent bona fide intermediates of the initiation process. Similarly, high-throughput sequencing-based ribosome profiling or "footprinting" approaches have allowed much progress in understanding the elongation phase of translation, and variants of them are beginning to reveal the remaining mysteries of initiation, as well as aspects of translation termination and ribosomal recycling. A current view on the eukaryotic initiation mechanism is presented here with an emphasis on how recent structural and footprinting results underpin axioms of the consensus model. Along the way, we further outline some contested mechanistic issues and major open questions still to be addressed. This article is categorized under: Translation > Translation Mechanisms Translation > Translation Regulation RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications.
Collapse
Affiliation(s)
- Nikolay E Shirokikh
- EMBL-Australia Collaborating Group, Department of Genome Sciences, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
- Victor Chang Cardiac Research Institute, Darlinghurst, Australia
| | - Thomas Preiss
- EMBL-Australia Collaborating Group, Department of Genome Sciences, The John Curtin School of Medical Research, The Australian National University, Canberra, Australia
- Victor Chang Cardiac Research Institute, Darlinghurst, Australia
| |
Collapse
|
21
|
Valášek LS, Zeman J, Wagner S, Beznosková P, Pavlíková Z, Mohammad MP, Hronová V, Herrmannová A, Hashem Y, Gunišová S. Embraced by eIF3: structural and functional insights into the roles of eIF3 across the translation cycle. Nucleic Acids Res 2017; 45:10948-10968. [PMID: 28981723 PMCID: PMC5737393 DOI: 10.1093/nar/gkx805] [Citation(s) in RCA: 80] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 08/31/2017] [Indexed: 12/31/2022] Open
Abstract
Protein synthesis is mediated via numerous molecules including the ribosome, mRNA, tRNAs, as well as translation initiation, elongation and release factors. Some of these factors play several roles throughout the entire process to ensure proper assembly of the preinitiation complex on the right mRNA, accurate selection of the initiation codon, errorless production of the encoded polypeptide and its proper termination. Perhaps, the most intriguing of these multitasking factors is the eukaryotic initiation factor eIF3. Recent evidence strongly suggests that this factor, which coordinates the progress of most of the initiation steps, does not come off the initiation complex upon subunit joining, but instead it remains bound to 80S ribosomes and gradually falls off during the first few elongation cycles to: (1) promote resumption of scanning on the same mRNA molecule for reinitiation downstream—in case of translation of upstream ORFs short enough to preserve eIF3 bound; or (2) come back during termination on long ORFs to fine tune its fidelity or, if signaled, promote programmed stop codon readthrough. Here, we unite recent structural views of the eIF3–40S complex and discus all known eIF3 roles to provide a broad picture of the eIF3’s impact on translational control in eukaryotic cells.
Collapse
Affiliation(s)
- Leoš Shivaya Valášek
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Jakub Zeman
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Susan Wagner
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Petra Beznosková
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Zuzana Pavlíková
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Mahabub Pasha Mohammad
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Vladislava Hronová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Anna Herrmannová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| | - Yaser Hashem
- CNRS, Architecture et Réactivité de l'ARN UPR9002, Université de Strasbourg, 67084 Strasbourg, France
| | - Stanislava Gunišová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague 142 20, the Czech Republic
| |
Collapse
|
22
|
Cate JHD. Human eIF3: from 'blobology' to biological insight. Philos Trans R Soc Lond B Biol Sci 2017; 372:rstb.2016.0176. [PMID: 28138064 PMCID: PMC5311922 DOI: 10.1098/rstb.2016.0176] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/16/2016] [Indexed: 02/06/2023] Open
Abstract
Translation in eukaryotes is highly regulated during initiation, a process impacted by numerous readouts of a cell's state. There are many cases in which cellular messenger RNAs likely do not follow the canonical ‘scanning’ mechanism of translation initiation, but the molecular mechanisms underlying these pathways are still being uncovered. Some RNA viruses such as the hepatitis C virus use highly structured RNA elements termed internal ribosome entry sites (IRESs) that commandeer eukaryotic translation initiation, by using specific interactions with the general eukaryotic translation initiation factor eIF3. Here, I present evidence that, in addition to its general role in translation, eIF3 in humans and likely in all multicellular eukaryotes also acts as a translational activator or repressor by binding RNA structures in the 5′-untranslated regions of specific mRNAs, analogous to the role of the mediator complex in transcription. Furthermore, eIF3 in multicellular eukaryotes also harbours a 5′ 7-methylguanosine cap-binding subunit—eIF3d—which replaces the general cap-binding initiation factor eIF4E in the translation of select mRNAs. Based on results from cell biological, biochemical and structural studies of eIF3, it is likely that human translation initiation proceeds through dozens of different molecular pathways, the vast majority of which remain to be explored. This article is part of the themed issue ‘Perspectives on the ribosome’.
Collapse
Affiliation(s)
- Jamie H D Cate
- Departments of Chemistry and Molecular and Cell Biology, University of California, Berkeley, CA 94720-3220, USA .,Lawrence Berkeley National Laboratory, Division of Molecular Biophysics and Integrated Bioimaging, Berkeley, CA 94720, USA
| |
Collapse
|
23
|
Obayashi E, Luna RE, Nagata T, Martin-Marcos P, Hiraishi H, Singh CR, Erzberger JP, Zhang F, Arthanari H, Morris J, Pellarin R, Moore C, Harmon I, Papadopoulos E, Yoshida H, Nasr ML, Unzai S, Thompson B, Aube E, Hustak S, Stengel F, Dagraca E, Ananbandam A, Gao P, Urano T, Hinnebusch AG, Wagner G, Asano K. Molecular Landscape of the Ribosome Pre-initiation Complex during mRNA Scanning: Structural Role for eIF3c and Its Control by eIF5. Cell Rep 2017; 18:2651-2663. [PMID: 28297669 DOI: 10.1016/j.celrep.2017.02.052] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 12/07/2016] [Accepted: 02/16/2017] [Indexed: 10/20/2022] Open
Abstract
During eukaryotic translation initiation, eIF3 binds the solvent-accessible side of the 40S ribosome and recruits the gate-keeper protein eIF1 and eIF5 to the decoding center. This is largely mediated by the N-terminal domain (NTD) of eIF3c, which can be divided into three parts: 3c0, 3c1, and 3c2. The N-terminal part, 3c0, binds eIF5 strongly but only weakly to the ribosome-binding surface of eIF1, whereas 3c1 and 3c2 form a stoichiometric complex with eIF1. 3c1 contacts eIF1 through Arg-53 and Leu-96, while 3c2 faces 40S protein uS15/S13, to anchor eIF1 to the scanning pre-initiation complex (PIC). We propose that the 3c0:eIF1 interaction diminishes eIF1 binding to the 40S, whereas 3c0:eIF5 interaction stabilizes the scanning PIC by precluding this inhibitory interaction. Upon start codon recognition, interactions involving eIF5, and ultimately 3c0:eIF1 association, facilitate eIF1 release. Our results reveal intricate molecular interactions within the PIC, programmed for rapid scanning-arrest at the start codon.
Collapse
Affiliation(s)
- Eiji Obayashi
- Shimane University School of Medicine, Izumo, Shimane 690-8504, Japan
| | - Rafael E Luna
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Takashi Nagata
- Institute of Advanced Energy, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Pilar Martin-Marcos
- Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Hiroyuki Hiraishi
- Molecular Cellular Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA
| | - Chingakham Ranjit Singh
- Molecular Cellular Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA
| | - Jan Peter Erzberger
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, 8093 Zurich, Switzerland
| | - Fan Zhang
- Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Haribabu Arthanari
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Jacob Morris
- Molecular Cellular Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA
| | - Riccardo Pellarin
- California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Chelsea Moore
- Molecular Cellular Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA
| | - Ian Harmon
- Molecular Cellular Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA
| | - Evangelos Papadopoulos
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Hisashi Yoshida
- Graduate School of Medical Life Science, Yokohama City University, Tsurumi-ku, Yokohama 230-0045, Japan; Drug Design Group, Kanagawa Academy of Science and Technology, Takatsu-ku, Kawasaki 213-0012, Japan
| | - Mahmoud L Nasr
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Satoru Unzai
- Graduate School of Medical Life Science, Yokohama City University, Tsurumi-ku, Yokohama 230-0045, Japan
| | - Brytteny Thompson
- Molecular Cellular Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA
| | - Eric Aube
- Molecular Cellular Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA
| | - Samantha Hustak
- Molecular Cellular Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA
| | - Florian Stengel
- Department of Biology, Institute of Molecular Systems Biology, ETH Zurich, 8093 Zurich, Switzerland
| | - Eddie Dagraca
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | | | - Philip Gao
- COBRE-PSF, University of Kansas, Lawrence, KS 66047, USA
| | - Takeshi Urano
- Shimane University School of Medicine, Izumo, Shimane 690-8504, Japan
| | - Alan G Hinnebusch
- Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA
| | - Gerhard Wagner
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115, USA
| | - Katsura Asano
- Molecular Cellular Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506, USA.
| |
Collapse
|
24
|
Hinnebusch AG. Structural Insights into the Mechanism of Scanning and Start Codon Recognition in Eukaryotic Translation Initiation. Trends Biochem Sci 2017; 42:589-611. [PMID: 28442192 DOI: 10.1016/j.tibs.2017.03.004] [Citation(s) in RCA: 196] [Impact Index Per Article: 28.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2017] [Revised: 03/12/2017] [Accepted: 03/20/2017] [Indexed: 12/21/2022]
Abstract
Initiation of translation on eukaryotic mRNAs generally follows the scanning mechanism, wherein a preinitiation complex (PIC) assembled on the small (40S) ribosomal subunit and containing initiator methionyl tRNAi (Met-tRNAi) scans the mRNA leader for an AUG codon. In a current model, the scanning PIC adopts an open conformation and rearranges to a closed state, with fully accommodated Met-tRNAi, upon AUG recognition. Evidence from recent high-resolution structures of PICs assembled with different ligands supports this model and illuminates the molecular functions of eukaryotic initiation factors eIF1, eIF1A, and eIF2 in restricting to AUG codons the transition to the closed conformation. They also reveal that the eIF3 complex interacts with multiple functional sites in the PIC, rationalizing its participation in numerous steps of initiation.
Collapse
Affiliation(s)
- Alan G Hinnebusch
- Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD 20892, USA.
| |
Collapse
|
25
|
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.
Collapse
|
26
|
Pisareva VP, Pisarev AV. DHX29 and eIF3 cooperate in ribosomal scanning on structured mRNAs during translation initiation. RNA (NEW YORK, N.Y.) 2016; 22:1859-1870. [PMID: 27733651 PMCID: PMC5113206 DOI: 10.1261/rna.057851.116] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/07/2016] [Accepted: 09/12/2016] [Indexed: 06/06/2023]
Abstract
Eukaryotic translation initiation is a complex process involving many components. eIF3 is a scaffold for multiple initiation factors and plays multiple roles in initiation, and DHX29 helicase enhances the formation of the 48S initiation complex on structured mRNAs. Because DHX29 is not a processive helicase, the mechanism underlying its activity is unclear. Here, we show that DHX29 establishes many points of contact with eIF3. In particular, the unique N terminus of DHX29 associates with the RNA recognition motif of eIF3b and the C terminus of the eIF3a subunits of eIF3, and the disruption of either contact impairs DHX29 activity. In turn, DHX29 has weak points of contact with mRNA in the 48S initiation complex, and the pathway taken by mRNA remains unchanged. These results exclude the direct role for this protein in unwinding. Thus, DHX29 and eIF3 cooperate in scanning on structured mRNAs. Our findings support previous genetic data on the role of eIF3 during scanning.
Collapse
Affiliation(s)
- Vera P Pisareva
- Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA
| | - Andrey V Pisarev
- Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA
| |
Collapse
|
27
|
Aitken CE, Beznosková P, Vlčkova V, Chiu WL, Zhou F, Valášek LS, Hinnebusch AG, Lorsch JR. Eukaryotic translation initiation factor 3 plays distinct roles at the mRNA entry and exit channels of the ribosomal preinitiation complex. eLife 2016; 5. [PMID: 27782884 PMCID: PMC5153249 DOI: 10.7554/elife.20934] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 10/25/2016] [Indexed: 11/13/2022] Open
Abstract
Eukaryotic translation initiation factor 3 (eIF3) is a central player in recruitment of the pre-initiation complex (PIC) to mRNA. We probed the effects on mRNA recruitment of a library of S. cerevisiae eIF3 functional variants spanning its 5 essential subunits using an in vitro-reconstituted system. Mutations throughout eIF3 disrupt its interaction with the PIC and diminish its ability to accelerate recruitment to a native yeast mRNA. Alterations to the eIF3a CTD and eIF3b/i/g significantly slow mRNA recruitment, and mutations within eIF3b/i/g destabilize eIF2•GTP•Met-tRNAi binding to the PIC. Using model mRNAs lacking contacts with the 40S entry or exit channels, we uncovered a critical role for eIF3 requiring the eIF3a NTD, in stabilizing mRNA interactions at the exit channel, and an ancillary role at the entry channel requiring residues of the eIF3a CTD. These functions are redundant: defects at each channel can be rescued by filling the other channel with mRNA. DOI:http://dx.doi.org/10.7554/eLife.20934.001 Cells use the genetic information stored within genes to build proteins, which are largely responsible for performing the molecular tasks essential for life. The ribosome is the molecular machine that translates the information within genes to assemble proteins in all cells, from bacteria to humans. To make a protein, the corresponding gene is first copied to make molecules of messenger ribonucleic acid (or mRNA for short). Then the ribosome binds to the mRNA in a process called translation initiation. Cells tightly regulate translation initiation so that they can decide which proteins to make, according to their needs and in response to changes in the environment. In fact, regulation of translation initiation is often disrupted during viral infections, cancer and other human diseases. A set of proteins called translation initiation factors drive translation initiation; the largest and least understood of these is called eIF3. Cells are unable to load the mRNA onto the ribosome without eIF3, which has two “arms” that sit near where the mRNA enters and exits the ribosome. Aitken et al. used mutant forms of eIF3 from genetically modified yeast to investigate how the arms of the protein work, and if they help the ribosome hold onto the mRNA. These experiments show that the two arms of eIF3 have unique roles. One arm sits near where mRNA exits the ribosome and is important for holding onto the mRNA. The other arm – which is near where mRNA enters the ribosome – helps hold the ribosome and other components of the translation machinery together. This arm may also help to open and close the channel through which messenger RNA enters the ribosome. The next challenges are to find out the precise role this arm plays in translation – in particular, how it helps to open and close the channel in the ribosome, and whether this helps the ribosome load the messenger RNA or even move along it. DOI:http://dx.doi.org/10.7554/eLife.20934.002
Collapse
Affiliation(s)
- Colin Echeverría Aitken
- Laboratory on the Mechanism and Regulation of Protein Synthesis, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
| | - Petra Beznosková
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Prague, Czech Republic
| | - Vladislava Vlčkova
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Prague, Czech Republic
| | - Wen-Ling Chiu
- Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
| | - Fujun Zhou
- Laboratory on the Mechanism and Regulation of Protein Synthesis, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
| | - Leoš Shivaya Valášek
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Prague, Czech Republic
| | - Alan G Hinnebusch
- Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
| | - Jon R Lorsch
- Laboratory on the Mechanism and Regulation of Protein Synthesis, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, United States
| |
Collapse
|
28
|
Wagner S, Herrmannová A, Šikrová D, Valášek LS. Human eIF3b and eIF3a serve as the nucleation core for the assembly of eIF3 into two interconnected modules: the yeast-like core and the octamer. Nucleic Acids Res 2016; 44:10772-10788. [PMID: 27924037 PMCID: PMC5159561 DOI: 10.1093/nar/gkw972] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2016] [Revised: 10/07/2016] [Accepted: 10/11/2016] [Indexed: 12/05/2022] Open
Abstract
The 12-subunit mammalian eIF3 is the largest and most complex translation initiation factor and has been implicated in numerous steps of translation initiation, termination and ribosomal recycling. Imbalanced eIF3 expression levels are observed in various types of cancer and developmental disorders, but the consequences of altered eIF3 subunit expression on its overall structure and composition, and on translation in general, remain unclear. We present the first complete in vivo study monitoring the effects of RNAi knockdown of each subunit of human eIF3 on its function, subunit balance and integrity. We show that the eIF3b and octameric eIF3a subunits serve as the nucleation core around which other subunits assemble in an ordered way into two interconnected modules: the yeast-like core and the octamer, respectively. In the absence of eIF3b neither module forms in vivo, whereas eIF3d knock-down results in severe proliferation defects with no impact on eIF3 integrity. Disrupting the octamer produces an array of subcomplexes with potential roles in translational regulation. This study, outlining the mechanism of eIF3 assembly and illustrating how imbalanced expression of eIF3 subunits impacts the factor's overall expression profile, thus provides a comprehensive guide to the human eIF3 complex and to the relationship between eIF3 misregulation and cancer.
Collapse
Affiliation(s)
- Susan Wagner
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague, 142 20, the Czech Republic
| | - Anna Herrmannová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague, 142 20, the Czech Republic
| | - Darina Šikrová
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague, 142 20, the Czech Republic
| | - Leoš Shivaya Valášek
- Laboratory of Regulation of Gene Expression, Institute of Microbiology ASCR, Videnska 1083, Prague, 142 20, the Czech Republic
| |
Collapse
|
29
|
Wang W, Xu M, Liu X, Tu J. The Rice Eukaryotic Translation Initiation Factor 3 Subunit e (OseIF3e) Influences Organ Size and Pollen Maturation. FRONTIERS IN PLANT SCIENCE 2016; 7:1399. [PMID: 27703462 PMCID: PMC5028392 DOI: 10.3389/fpls.2016.01399] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 09/02/2016] [Indexed: 05/24/2023]
Abstract
Eukaryotic translation initiation factor 3 (eIF3) is a large protein complex that participates in most translation initiation processes. While eIF3 has been well characterized, less is known about the roles of individual eIF3 subunits, particularly in plants. Here, we identified and characterized OseIF3e in rice (Oryza sativa L.). OseIF3e was constitutively expressed in various tissues, but most strongly in vigorously growing organs. Transgenic OseIF3e-silenced rice plants showed inhibited growth in seedling and vegetative stages. Repression of OseIF3e led to defects in pollen maturation but did not affect pollen mitosis. In rice, eIF3e interacted with eIF3 subunits b, d, e, f, h, and k, and with eIF6, forming homo- and heterodimers to initiate translation. Furthermore, OseIF3e was shown by yeast two-hybrid assay to specifically bind to inhibitors of cyclin-dependent kinases 1, 5, and 6. This interaction was mediated by the sequence of amino acid residues at positions 118-138, which included a conserved motif (IGPEQIETLYQFAKF). These results suggested although OseIF3e is not a "functional core" subunit of eIF3, it still plays crucial roles in rice growth and development, in combination with other factors. We proposed a pathway by which OseIF3e influence organ size and pollen maturation in rice, providing an opportunity to optimize plant architecture for crop breeding.
Collapse
|
30
|
Schmidt C, Beilsten-Edmands V, Robinson CV. Insights into Eukaryotic Translation Initiation from Mass Spectrometry of Macromolecular Protein Assemblies. J Mol Biol 2015; 428:344-356. [PMID: 26497764 DOI: 10.1016/j.jmb.2015.10.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Revised: 09/28/2015] [Accepted: 10/14/2015] [Indexed: 02/05/2023]
Abstract
Translation initiation in eukaryotes requires the interplay of at least 10 initiation factors that interact at the different steps of this phase of gene expression. The interactions of initiation factors and related proteins are in general controlled by phosphorylation, which serves as a regulatory switch to turn protein translation on or off. The structures of initiation factors and a complete description of their post-translational modification (PTM) status are therefore required in order to fully understand these processes. In recent years, mass spectrometry has contributed considerably to provide this information and nowadays is proving to be indispensable when studying dynamic heterogeneous protein complexes such as the eukaryotic initiation factors. Herein, we highlight mass spectrometric approaches commonly applied to identify interacting subunits and their PTMs and the structural techniques that allow the architecture of protein complexes to be assessed. We present recent structural investigations of initiation factors and their interactions with other factors and with ribosomes and we assess the models generated. These models allow us to locate PTMs within initiation factor complexes and to highlight possible roles for phosphorylation sites in regulating interaction interfaces.
Collapse
Affiliation(s)
- Carla Schmidt
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom.
| | - Victoria Beilsten-Edmands
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom.
| | - Carol V Robinson
- Department of Chemistry, Physical and Theoretical Chemistry Laboratory, University of Oxford, South Parks Road, Oxford OX1 3QZ, United Kingdom.
| |
Collapse
|
31
|
Ghosh A, Komar AA. Eukaryote-specific extensions in ribosomal proteins of the small subunit: Structure and function. ACTA ACUST UNITED AC 2015; 3:e999576. [PMID: 26779416 DOI: 10.1080/21690731.2014.999576] [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] [Received: 10/16/2014] [Revised: 12/03/2014] [Accepted: 12/12/2014] [Indexed: 01/05/2023]
Abstract
High-resolution structures of yeast ribosomes have improved our understanding of the architecture and organization of eukaryotic rRNA and proteins, as well as eukaryote-specific extensions present in some conserved ribosomal proteins. Despite this progress, assignment of specific functions to individual proteins and/or eukaryote-specific protein extensions remains challenging. It has been suggested that eukaryote-specific extensions of conserved proteins from the small ribosomal subunit may facilitate eukaryote-specific reactions in the initiation phase of protein synthesis. This review summarizes emerging data describing the structural and functional significance of eukaryote-specific extensions of conserved small ribosomal subunit proteins, particularly their possible roles in recruitment and spatial organization of eukaryote-specific initiation factors.
Collapse
Affiliation(s)
- Arnab Ghosh
- Center for Gene Regulation in Health and Disease; Department of Biological, Geological and Environmental Sciences; Cleveland State University ; Cleveland, OH USA
| | - Anton A Komar
- Center for Gene Regulation in Health and Disease; Department of Biological, Geological and Environmental Sciences; Cleveland State University ; Cleveland, OH USA
| |
Collapse
|
32
|
Abstract
In eukaryotes, the translation initiation codon is generally identified by the scanning mechanism, wherein every triplet in the messenger RNA leader is inspected for complementarity to the anticodon of methionyl initiator transfer RNA (Met-tRNAi). Binding of Met-tRNAi to the small (40S) ribosomal subunit, in a ternary complex (TC) with eIF2-GTP, is stimulated by eukaryotic initiation factor 1 (eIF1), eIF1A, eIF3, and eIF5, and the resulting preinitiation complex (PIC) joins the 5' end of mRNA preactivated by eIF4F and poly(A)-binding protein. RNA helicases remove secondary structures that impede ribosome attachment and subsequent scanning. Hydrolysis of eIF2-bound GTP is stimulated by eIF5 in the scanning PIC, but completion of the reaction is impeded at non-AUG triplets. Although eIF1 and eIF1A promote scanning, eIF1 and possibly the C-terminal tail of eIF1A must be displaced from the P decoding site to permit base-pairing between Met-tRNAi and the AUG codon, as well as to allow subsequent phosphate release from eIF2-GDP. A second GTPase, eIF5B, catalyzes the joining of the 60S subunit to produce an 80S initiation complex that is competent for elongation.
Collapse
Affiliation(s)
- Alan G Hinnebusch
- Laboratory of Gene Regulation and Development, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, Maryland 20892;
| |
Collapse
|
33
|
Luna RE, Arthanari H, Hiraishi H, Akabayov B, Tang L, Cox C, Markus MA, Luna LE, Ikeda Y, Watanabe R, Bedoya E, Yu C, Alikhan S, Wagner G, Asano K. The interaction between eukaryotic initiation factor 1A and eIF5 retains eIF1 within scanning preinitiation complexes. Biochemistry 2013; 52:9510-8. [PMID: 24319994 PMCID: PMC3917153 DOI: 10.1021/bi4009775] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Scanning of the mRNA transcript by the preinitiation complex (PIC) requires a panel of eukaryotic initiation factors, which includes eIF1 and eIF1A, the main transducers of stringent AUG selection. eIF1A plays an important role in start codon recognition; however, its molecular contacts with eIF5 are unknown. Using nuclear magnetic resonance, we unveil eIF1A's binding surface on the carboxyl-terminal domain of eIF5 (eIF5-CTD). We validated this interaction by observing that eIF1A does not bind to an eIF5-CTD mutant, altering the revealed eIF1A interaction site. We also found that the interaction between eIF1A and eIF5-CTD is conserved between humans and yeast. Using glutathione S-transferase pull-down assays of purified proteins, we showed that the N-terminal tail (NTT) of eIF1A mediates the interaction with eIF5-CTD and eIF1. Genetic evidence indicates that overexpressing eIF1 or eIF5 suppresses the slow growth phenotype of eIF1A-NTT mutants. These results suggest that the eIF1A-eIF5-CTD interaction during scanning PICs contributes to the maintenance of eIF1 within the open PIC.
Collapse
Affiliation(s)
- Rafael E. Luna
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Haribabu Arthanari
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Hiroyuki Hiraishi
- Molecular, Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506
| | - Barak Akabayov
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Leiming Tang
- Molecular, Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506
| | - Christian Cox
- Molecular, Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506
| | - Michelle A. Markus
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Lunet E. Luna
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Yuka Ikeda
- Molecular, Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506
| | - Ryosuke Watanabe
- Molecular, Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506
| | - Edward Bedoya
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Cathy Yu
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Shums Alikhan
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Gerhard Wagner
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115
| | - Katsura Asano
- Molecular, Cellular and Developmental Biology Program, Division of Biology, Kansas State University, Manhattan, KS 66506
| |
Collapse
|
34
|
Smith MD, Gu Y, Querol-Audí J, Vogan JM, Nitido A, Cate JHD. Human-like eukaryotic translation initiation factor 3 from Neurospora crassa. PLoS One 2013; 8:e78715. [PMID: 24250809 PMCID: PMC3826745 DOI: 10.1371/journal.pone.0078715] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Accepted: 09/22/2013] [Indexed: 02/05/2023] Open
Abstract
Eukaryotic translation initiation factor 3 (eIF3) is a key regulator of translation initiation, but its in vivo assembly and molecular functions remain unclear. Here we show that eIF3 from Neurospora crassa is structurally and compositionally similar to human eIF3. N. crassa eIF3 forms a stable 12-subunit complex linked genetically and biochemically to the 13th subunit, eIF3j, which in humans modulates mRNA start codon selection. Based on N. crassa genetic analysis, most subunits in eIF3 are essential. Subunits that can be deleted (e, h, k and l) map to the right side of the eIF3 complex, suggesting that they may coordinately regulate eIF3 function. Consistent with this model, subunits eIF3k and eIF3l are incorporated into the eIF3 complex as a pair, and their insertion depends on the presence of subunit eIF3h, a key regulator of vertebrate development. Comparisons to other eIF3 complexes suggest that eIF3 assembles around an eIF3a and eIF3c dimer, which may explain the coordinated regulation of human eIF3 levels. Taken together, these results show that Neurospora crassa eIF3 provides a tractable system for probing the structure and function of human-like eIF3 in the context of living cells.
Collapse
Affiliation(s)
- M. Duane Smith
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Yu Gu
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Jordi Querol-Audí
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Jacob M. Vogan
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Adam Nitido
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
| | - Jamie H. D. Cate
- Department of Molecular and Cell Biology, University of California, Berkeley, California, United States of America
- Department of Chemistry, University of California, Berkeley, California, United States of America
- Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America
- * E-mail:
| |
Collapse
|
35
|
Kim JT, Lee SJ, Kim BY, Lee CH, Yeom YI, Choe YK, Yoon DY, Chae SK, Kim JW, Yang Y, Lim JS, Lee HG. Caspase-mediated cleavage and DNase activity of the translation initiation factor 3, subunit G (eIF3g). FEBS Lett 2013; 587:3668-74. [DOI: 10.1016/j.febslet.2013.09.027] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Revised: 09/12/2013] [Accepted: 09/20/2013] [Indexed: 11/26/2022]
|
36
|
Salsman J, Pinder J, Tse B, Corkery D, Dellaire G. The translation initiation factor 3 subunit eIF3K interacts with PML and associates with PML nuclear bodies. Exp Cell Res 2013; 319:2554-65. [PMID: 24036361 DOI: 10.1016/j.yexcr.2013.09.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2012] [Revised: 08/08/2013] [Accepted: 09/02/2013] [Indexed: 12/17/2022]
Abstract
The promyelocytic leukemia protein (PML) is a tumor suppressor protein that regulates a variety of important cellular processes, including gene expression, DNA repair and cell fate decisions. Integral to its function is the ability of PML to form nuclear bodies (NBs) that serve as hubs for the interaction and modification of over 90 cellular proteins. There are seven canonical isoforms of PML, which encode diverse C-termini generated by alternative pre-mRNA splicing. Recruitment of specific cellular proteins to PML NBs is mediated by protein-protein interactions with individual PML isoforms. Using a yeast two-hybrid screen employing peptide sequences unique to PML isoform I (PML-I), we identified an interaction with the eukaryotic initiation factor 3 subunit K (eIF3K), and in the process identified a novel eIF3K isoform, which we term eIF3K-2. We further demonstrate that eIF3K and PML interact both in vitro via pull-down assays, as well as in vivo within human cells by co-immunoprecipitation and co-immunofluorescence. In addition, eIF3K isoform 2 (eIF3K-2) colocalizes to PML bodies, particularly those enriched in PML-I, while eIF3K isoform 1 associates poorly with PML NBs. Thus, we report eIF3K as the first known subunit of the eIF3 translation pre-initiation complex to interact directly with the PML protein, and provide data implicating alternative splicing of both PML and eIF3K as a possible regulatory mechanism for eIF3K localization at PML NBs.
Collapse
Affiliation(s)
- Jayme Salsman
- Department of Pathology, Dalhousie University, P.O. Box 15000, Halifax, Nova Scotia, Canada B3H 4R2
| | | | | | | | | |
Collapse
|
37
|
Zeng L, Wan Y, Li D, Wu J, Shao M, Chen J, Hui L, Ji H, Zhu X. The m subunit of murine translation initiation factor eIF3 maintains the integrity of the eIF3 complex and is required for embryonic development, homeostasis, and organ size control. J Biol Chem 2013; 288:30087-30093. [PMID: 24003236 DOI: 10.1074/jbc.m113.506147] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Mammalian eIF3 is composed of 13 subunits and is the largest eukaryotic initiation factor. eIF3 plays a key role in protein biosynthesis. However, it is not fully understood how different subunits contribute to the structural integrity and function of the eIF3 complex. Whether eIF3 is essential for embryonic development and homeostasis is also not known. Here, we show that eIF3m null embryos are lethal at the peri-implantation stage. Compound heterozygotes (eIF3m(flox)(/-)) or FABP4-Cre-mediated conditional knock-out mice are lethal at mid-gestation stages. Although the heterozygotes are viable, they show markedly reduced organ size and diminished body weight. Acute ablation of eIF3m in adult mouse liver leads to rapidly decreased body weight and death within 2 weeks; these effects are correlated with a severe decline of protein biogenesis in the liver. Protein analyses reveal that eIF3m deficiency significantly impairs the integrity of the eIF3 complex due to down-regulation of multiple other subunits. Two of the subunits, eIF3f and eIF3h, are stabilized by eIF3m through subcomplex formation. Therefore, eIF3m is required for the structural integrity and translation initiation function of eIF3. Furthermore, not only is eIF3m an essential gene, but its expression level is also important for mouse embryonic development and the control of organ size.
Collapse
Affiliation(s)
- Liyong Zeng
- From the State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, and
| | - Yihan Wan
- From the State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, and
| | - Dan Li
- From the State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, and
| | - Jing Wu
- the Model Animal Research Center, Nanjing University, Nanjing, Jiangsu 210061, China
| | - Mengle Shao
- the Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China and
| | - Jiong Chen
- the Model Animal Research Center, Nanjing University, Nanjing, Jiangsu 210061, China
| | - Lijian Hui
- From the State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, and
| | - Hongbin Ji
- From the State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, and
| | - Xueliang Zhu
- From the State Key Laboratory of Cell Biology, Institute of Biochemistry and Cell Biology, and.
| |
Collapse
|
38
|
The translational factor eIF3f: the ambivalent eIF3 subunit. Cell Mol Life Sci 2013; 70:3603-16. [PMID: 23354061 PMCID: PMC3771369 DOI: 10.1007/s00018-013-1263-y] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2012] [Revised: 12/18/2012] [Accepted: 01/07/2013] [Indexed: 11/15/2022]
Abstract
The regulation of the protein synthesis has a crucial role in governing the eukaryotic cell growth. Subtle changes of proteins involved in the translation process may alter the rate of the protein synthesis and modify the cell fate by shifting the balance from normal status into a tumoral or apoptotic one. The largest eukaryotic initiation factor involved in translation regulation is eIF3. Amongst the 13 factors constituting eIF3, the f subunit finely regulates this balance in a cell-type-specific manner. Loss of this factor causes malignancy in several cells, and atrophy in normal muscle cells. The intracellular interacting partners which influence its physiological significance in both cancer and muscle cells are detailed in this review. By delineating the global interaction network of this factor and by clarifying its intracellular role, it becomes apparent that the f subunit represents a promising candidate molecule to use for biotherapeutic applications.
Collapse
|
39
|
Khoshnevis S, Hauer F, Milón P, Stark H, Ficner R. Novel insights into the architecture and protein interaction network of yeast eIF3. RNA (NEW YORK, N.Y.) 2012; 18:2306-19. [PMID: 23105002 PMCID: PMC3504681 DOI: 10.1261/rna.032532.112] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Accepted: 09/17/2012] [Indexed: 05/20/2023]
Abstract
Translation initiation in eukaryotes is a multistep process requiring the orchestrated interaction of several eukaryotic initiation factors (eIFs). The largest of these factors, eIF3, forms the scaffold for other initiation factors, promoting their binding to the 40S ribosomal subunit. Biochemical and structural studies on eIF3 need highly pure eIF3. However, natively purified eIF3 comprise complexes containing other proteins such as eIF5. Therefore we have established in vitro reconstitution protocols for Saccharomyces cerevisiae eIF3 using its five recombinantly expressed and purified subunits. This reconstituted eIF3 complex (eIF3(rec)) exhibits the same size and activity as the natively purified eIF3 (eIF3(nat)). The homogeneity and stoichiometry of eIF3(rec) and eIF3(nat) were confirmed by analytical size exclusion chromatography, mass spectrometry, and multi-angle light scattering, demonstrating the presence of one copy of each subunit in the eIF3 complex. The reconstituted and native eIF3 complexes were compared by single-particle electron microscopy showing a high degree of structural conservation. The interaction network between eIF3 proteins was studied by means of limited proteolysis, analytical size exclusion chromatography, in vitro binding assays, and isothermal titration calorimetry, unveiling distinct protein domains and subcomplexes that are critical for the integrity of the protein network in yeast eIF3. Taken together, the data presented here provide a novel procedure to obtain highly pure yeast eIF3, suitable for biochemical and structural analysis, in addition to a detailed picture of the network of protein interactions within this complex.
Collapse
Affiliation(s)
- Sohail Khoshnevis
- Department of Molecular Structural Biology, Institute of Microbiology and Genetics, Georg-August University Göttingen, 37077 Göttingen, Germany
| | | | - Pohl Milón
- Department of Physical Biochemistry, Max-Planck-Institute for Biophysical Chemistry, 37077 Göttingen, Germany
| | - Holger Stark
- Research Group 3D Electron Cryo-Microscopy
- Department of Molecular Cryo-Electron Microscopy, Institute of Microbiology and Genetics, Georg-August University Göttingen, 37077 Göttingen, Germany
| | - Ralf Ficner
- Department of Molecular Structural Biology, Institute of Microbiology and Genetics, Georg-August University Göttingen, 37077 Göttingen, Germany
- Corresponding authorE-mail
| |
Collapse
|
40
|
Karásková M, Gunišová S, Herrmannová A, Wagner S, Munzarová V, Valášek LS. Functional characterization of the role of the N-terminal domain of the c/Nip1 subunit of eukaryotic initiation factor 3 (eIF3) in AUG recognition. J Biol Chem 2012; 287:28420-34. [PMID: 22718758 PMCID: PMC3436577 DOI: 10.1074/jbc.m112.386656] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
In eukaryotes, for a protein to be synthesized, the 40 S subunit has to first scan the 5′-UTR of the mRNA until it has encountered the AUG start codon. Several initiation factors that ensure high fidelity of AUG recognition were identified previously, including eIF1A, eIF1, eIF2, and eIF5. In addition, eIF3 was proposed to coordinate their functions in this process as well as to promote their initial binding to 40 S subunits. Here we subjected several previously identified segments of the N-terminal domain (NTD) of the eIF3c/Nip1 subunit, which mediates eIF3 binding to eIF1 and eIF5, to semirandom mutagenesis to investigate the molecular mechanism of eIF3 involvement in these reactions. Three major classes of mutant substitutions or internal deletions were isolated that affect either the assembly of preinitiation complexes (PICs), scanning for AUG, or both. We show that eIF5 binds to the extreme c/Nip1-NTD (residues 1–45) and that impairing this interaction predominantly affects the PIC formation. eIF1 interacts with the region (60–137) that immediately follows, and altering this contact deregulates AUG recognition. Together, our data indicate that binding of eIF1 to the c/Nip1-NTD is equally important for its initial recruitment to PICs and for its proper functioning in selecting the translational start site.
Collapse
Affiliation(s)
- Martina Karásková
- Laboratory of Regulation of Gene Expression, Institute of Microbiology Academy of Sciences of the Czech Republic, Videnska 1083, Prague 4, 142 20, the Czech Republic
| | | | | | | | | | | |
Collapse
|
41
|
Neusiedler J, Mocquet V, Limousin T, Ohlmann T, Morris C, Jalinot P. INT6 interacts with MIF4GD/SLIP1 and is necessary for efficient histone mRNA translation. RNA (NEW YORK, N.Y.) 2012; 18:1163-1177. [PMID: 22532700 PMCID: PMC3358639 DOI: 10.1261/rna.032631.112] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/02/2012] [Accepted: 03/06/2012] [Indexed: 05/31/2023]
Abstract
The INT6/EIF3E protein has been implicated in mouse and human breast carcinogenesis. This subunit of the eIF3 translation initiation factor that includes a PCI domain exhibits specific features such as presence in the nucleus and ability to interact with other important cellular protein complexes like the 26S proteasome and the COP9 signalosome. It has been previously shown that INT6 was not essential for bulk translation, and this protein is considered to regulate expression of specific mRNAs. Based on the results of a two-hybrid screen performed with INT6 as bait, we characterize in this article the MIF4GD/SLIP1 protein as an interactor of this eIF3 subunit. MIF4GD was previously shown to associate with SLBP, which binds the stem-loop located at the 3' end of the histone mRNAs, and to be necessary for efficient translation of these cell cycle-regulated mRNAs that lack a poly(A) tail. In line with the interaction of both proteins, we show using the RNA interference approach that INT6 is also essential to S-phase histone mRNA translation. This was observed by analyzing expression of endogenous histones and by testing heterologous constructs placing the luciferase reporter gene under the control of the stem-loop element of various histone genes. With such a reporter plasmid, silencing and overexpression of INT6 exerted opposite effects. In agreement with these results, INT6 and MIF4GD were observed to colocalize in cytoplasmic foci. We conclude from these data that INT6, by establishing interactions with MIF4GD and SLBP, plays an important role in translation of poly(A) minus histone mRNAs.
Collapse
Affiliation(s)
- Julia Neusiedler
- Laboratoire de Biologie Moléculaire de la Cellule, Unité Mixte de Recherche 5239, Centre National de la Recherche Scientifique, Ecole Normale Supérieure de Lyon, 69364 Lyon cedex 07, France
| | - Vincent Mocquet
- Laboratoire de Biologie Moléculaire de la Cellule, Unité Mixte de Recherche 5239, Centre National de la Recherche Scientifique, Ecole Normale Supérieure de Lyon, 69364 Lyon cedex 07, France
| | - Taran Limousin
- Virologie Humaine, Unité 758, Institut National de la Santé et de la Recherche Médicale, Ecole Normale Supérieure de Lyon, 69364 Lyon cedex 07, France
| | - Theophile Ohlmann
- Virologie Humaine, Unité 758, Institut National de la Santé et de la Recherche Médicale, Ecole Normale Supérieure de Lyon, 69364 Lyon cedex 07, France
| | - Christelle Morris
- Laboratoire de Biologie Moléculaire de la Cellule, Unité Mixte de Recherche 5239, Centre National de la Recherche Scientifique, Ecole Normale Supérieure de Lyon, 69364 Lyon cedex 07, France
| | - Pierre Jalinot
- Laboratoire de Biologie Moléculaire de la Cellule, Unité Mixte de Recherche 5239, Centre National de la Recherche Scientifique, Ecole Normale Supérieure de Lyon, 69364 Lyon cedex 07, France
| |
Collapse
|
42
|
Huang CY, Chen JY, Wu SC, Tan CH, Tzeng RY, Lu PJ, Wu YF, Chen RH, Wu YC. C. elegans EIF-3.K promotes programmed cell death through CED-3 caspase. PLoS One 2012; 7:e36584. [PMID: 22590572 PMCID: PMC3348885 DOI: 10.1371/journal.pone.0036584] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2012] [Accepted: 04/10/2012] [Indexed: 12/28/2022] Open
Abstract
Programmed cell death (apoptosis) is essential for the development and homeostasis of metazoans. The central step in the execution of programmed cell death is the activation of caspases. In C. elegans, the core cell death regulators EGL-1(a BH3 domain-containing protein), CED-9 (Bcl-2), and CED-4 (Apaf-1) act in an inhibitory cascade to activate the CED-3 caspase. Here we have identified an additional component eif-3.K (eukaryotic translation initiation factor 3 subunit k) that acts upstream of ced-3 to promote programmed cell death. The loss of eif-3.K reduced cell deaths in both somatic and germ cells, whereas the overexpression of eif-3.K resulted in a slight but significant increase in cell death. Using a cell-specific promoter, we show that eif-3.K promotes cell death in a cell-autonomous manner. In addition, the loss of eif-3.K significantly suppressed cell death-induced through the overexpression of ced-4, but not ced-3, indicating a distinct requirement for eif-3.K in apoptosis. Reciprocally, a loss of ced-3 suppressed cell death induced by the overexpression of eif-3.K. These results indicate that eif-3.K requires ced-3 to promote programmed cell death and that eif-3.K acts upstream of ced-3 to promote this process. The EIF-3.K protein is ubiquitously expressed in embryos and larvae and localizes to the cytoplasm. A structure-function analysis revealed that the 61 amino acid long WH domain of EIF-3.K, potentially involved in protein-DNA/RNA interactions, is both necessary and sufficient for the cell death-promoting activity of EIF-3.K. Because human eIF3k was able to partially substitute for C. elegans eif-3.K in the promotion of cell death, this WH domain-dependent EIF-3.K-mediated cell death process has potentially been conserved throughout evolution.
Collapse
Affiliation(s)
- Chun-Yi Huang
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
| | - Jia-Yun Chen
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
- Institute of Molecular Medicine, National Taiwan University, Taipei, Taiwan
| | - Shu-Chun Wu
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
| | - Chieh-Hsiang Tan
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
| | - Ruei-Ying Tzeng
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
| | - Pei-Ju Lu
- Institute of Molecular Medicine, National Taiwan University, Taipei, Taiwan
| | - Yu-Feng Wu
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
| | - Ruey-Hwa Chen
- Institute of Molecular Medicine, National Taiwan University, Taipei, Taiwan
- Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
- * E-mail: (YCW); (RHC)
| | - Yi-Chun Wu
- Institute of Molecular and Cellular Biology, National Taiwan University, Taipei, Taiwan
- Center for Systems Biology, National Taiwan University, Taipei, Taiwan
- Research Center for Developmental Biology and Regenerative Medicine, National Taiwan University, Taipei, Taiwan
- Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
- * E-mail: (YCW); (RHC)
| |
Collapse
|
43
|
Molecular mechanism of scanning and start codon selection in eukaryotes. Microbiol Mol Biol Rev 2012; 75:434-67, first page of table of contents. [PMID: 21885680 DOI: 10.1128/mmbr.00008-11] [Citation(s) in RCA: 281] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
The correct translation of mRNA depends critically on the ability to initiate at the right AUG codon. For most mRNAs in eukaryotic cells, this is accomplished by the scanning mechanism, wherein the small (40S) ribosomal subunit attaches to the 5' end of the mRNA and then inspects the leader base by base for an AUG in a suitable context, using complementarity with the anticodon of methionyl initiator tRNA (Met-tRNAiMet) as the key means of identifying AUG. Over the past decade, a combination of yeast genetics, biochemical analysis in reconstituted systems, and structural biology has enabled great progress in deciphering the mechanism of ribosomal scanning. A robust molecular model now exists, describing the roles of initiation factors, notably eukaryotic initiation factor 1 (eIF1) and eIF1A, in stabilizing an "open" conformation of the 40S subunit with Met-tRNAiMet bound in a low-affinity state conducive to scanning and in triggering rearrangement into a "closed" conformation incompatible with scanning, which features Met-tRNAiMet more tightly bound to the "P" site and base paired with AUG. It has also emerged that multiple DEAD-box RNA helicases participate in producing a single-stranded "landing pad" for the 40S subunit and in removing the secondary structure to enable the mRNA to traverse the 40S mRNA-binding channel in the single-stranded form for base-by-base inspection in the P site.
Collapse
|
44
|
Kouba T, Rutkai E, Karásková M, Valášek LS. The eIF3c/NIP1 PCI domain interacts with RNA and RACK1/ASC1 and promotes assembly of translation preinitiation complexes. Nucleic Acids Res 2011; 40:2683-99. [PMID: 22123745 PMCID: PMC3315329 DOI: 10.1093/nar/gkr1083] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Several subunits of the multifunctional eukaryotic translation initiation factor 3 (eIF3) contain well-defined domains. Among them is the conserved bipartite PCI domain, typically serving as the principal scaffold for multisubunit 26S proteasome lid, CSN and eIF3 complexes, which constitutes most of the C-terminal region of the c/NIP1 subunit. Interestingly, the c/NIP1-PCI domain is exceptional in that its deletion, despite being lethal, does not affect eIF3 integrity. Here, we show that a short C-terminal truncation and two clustered mutations directly disturbing the PCI domain produce lethal or slow growth phenotypes and significantly reduce amounts of 40S-bound eIF3 and eIF5 in vivo. The extreme C-terminus directly interacts with blades 1–3 of the small ribosomal protein RACK1/ASC1, which is a part of the 40S head, and, consistently, deletion of the ASC1 coding region likewise affects eIF3 association with ribosomes. The PCI domain per se shows strong but unspecific binding to RNA, for the first time implicating this typical protein–protein binding domain in mediating protein–RNA interactions also. Importantly, as our clustered mutations severely reduce RNA binding, we conclude that the c/NIP1 C-terminal region forms an important intermolecular bridge between eIF3 and the 40S head region by contacting RACK1/ASC1 and most probably 18S rRNA.
Collapse
Affiliation(s)
- Tomáš Kouba
- Laboratory of Regulation of Gene Expression, Institute of Microbiology AVCR, v.v.i., Prague, the Czech Republic
| | | | | | | |
Collapse
|
45
|
eIF5 has GDI activity necessary for translational control by eIF2 phosphorylation. Nature 2010; 465:378-81. [PMID: 20485439 PMCID: PMC2875157 DOI: 10.1038/nature09003] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2009] [Accepted: 03/10/2010] [Indexed: 11/23/2022]
Abstract
In protein synthesis initiation, the eukaryotic translation initiation factor (eIF) 2 (a G protein) functions in its GTP-bound state to deliver initiator methionyl-tRNA (tRNAiMet) to the small ribosomal subunit and is necessary for protein synthesis in all cells1,2. Phosphorylation of eIF2 [eIF2(αP)] is critical for translational control in diverse settings including nutrient deprivation, viral infection and memory formation3,4,5. eIF5 functions in start site selection as a GTPase accelerating protein (GAP) for the eIF2•GTP•tRNAiMet ternary complex (TC) within the ribosome bound pre-initiation complex6,7,8. Here we define new regulatory functions of eIF5 in the recycling of eIF2 from its inactive eIF2•GDP state between successive rounds of translation initiation. Firstly we show that eIF5 stabilizes the binding of GDP to eIF2 and is therefore a bi-functional protein that acts as a GDP dissociation inhibitor (GDI). We find that this activity is independent of the GAP function and identify conserved residues within eIF5 that are necessary for this role. In addition we show that eIF5 is a critical component of the eIF2(αP) regulatory complex that inhibits the activity of the guanine-nucleotide exchange factor (GEF) eIF2B. Together our studies define a new step in the translation initiation pathway, one that is critical for normal translational controls.
Collapse
|
46
|
Higareda-Mendoza AE, Pardo-Galván MA. Expression of human eukaryotic initiation factor 3f oscillates with cell cycle in A549 cells and is essential for cell viability. Cell Div 2010; 5:10. [PMID: 20462454 PMCID: PMC2877012 DOI: 10.1186/1747-1028-5-10] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2009] [Accepted: 05/13/2010] [Indexed: 11/10/2022] Open
Abstract
Background Transcriptional and postranslational regulation of the cell cycle has been widely studied. However, there is scarce knowledge concerning translational control of this process. Several mammalian eukaryotic initiation factors (eIFs) seem to be implicated in controlling cell proliferation. In this work, we investigated if the human eIF3f expression and function is cell cycle related. Results The human eIF3f expression has been found to be upregulated in growth-stimulated A549 cells and downregulated in G0. Western blot analysis and eIF3f promotor-luciferase fusions revealed that eIF3f expression peaks twice in the cell cycle: in the S and the M phases. Deregulation of eIF3f expression negatively affects cell viability and induces apoptosis. Conclusions The expression pattern of human eIF3f during the cell cycle confirms that this gene is cell division related. The fact that eIF3f expression peaks in two cell cycle phases raises the possibility that this gene may exert a differential function in the S and M phases. Our results strongly suggest that eIF3f is essential for cell proliferation.
Collapse
Affiliation(s)
- Ana E Higareda-Mendoza
- Departmento de Biología Molecular, Instituto de Investigaciones Químico-Biológicas, Universidad Michoacana de San Nicolás de Hidalgo, Morelia, Michoacán, México.
| | | |
Collapse
|
47
|
Elantak L, Wagner S, Herrmannová A, Karásková M, Rutkai E, Lukavsky PJ, Valásek L. The indispensable N-terminal half of eIF3j/HCR1 cooperates with its structurally conserved binding partner eIF3b/PRT1-RRM and with eIF1A in stringent AUG selection. J Mol Biol 2010; 396:1097-116. [PMID: 20060839 PMCID: PMC2824034 DOI: 10.1016/j.jmb.2009.12.047] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2009] [Revised: 12/17/2009] [Accepted: 12/22/2009] [Indexed: 11/13/2022]
Abstract
Despite the recent progress in our understanding of the numerous
functions of individual subunits of eukaryotic translation initiation factor 3
(eIF3), there is still only little known on the molecular level. Using NMR
spectroscopy, we determined the first solution structure of an interaction
between eIF3 subunits. We revealed that a conserved tryptophan residue in the
human eIF3j N-terminal acidic domain (NTA) is held in the helix α1
– loop L5 hydrophobic pocket of the human eIF3b-RRM. Mutating the
corresponding “pocket” residues in its yeast orthologue reduces
cellular growth rate, eliminates eIF3j/HCR1 association with eIF3b/PRT1
in vitro and in vivo, affects
40S-occupancy of eIF3, and produces a leaky scanning defect indicative of a
deregulation of the AUG selection process. Unexpectedly, we found that the
N-terminal half (NTD) of eIF3j/HCR1 containing the NTA motif is indispensable
and sufficient for wild-type growth of yeast cells. Furthermore, we demonstrate
that deletion of either j/HCR1 or its NTD only, or mutating the key tryptophan
residues results in the severe leaky scanning phenotype partially suppressible
by overexpressed eIF1A, which is thought to stabilize properly formed
pre-initiation complexes at the correct start codon. These findings indicate
that eIF3j/HCR1 remains associated with the scanning pre-initiation complexes
and does not dissociate from the small ribosomal subunit upon mRNA recruitment
as previously believed. Finally, we provide further support for earlier mapping
of the ribosomal binding site for human eIF3j by identifying specific
interactions of eIF3j/HCR1 with small ribosomal proteins RPS2 and RPS23 located
in the vicinity of the mRNA entry channel. Taken together we propose that
eIF3j/HCR1 closely co-operates with eIF3b/PRT1-RRM and eIF1A on the ribosome to
ensure proper formation of the scanning-arrested conformation required for
stringent AUG recognition.
Collapse
Affiliation(s)
- Latifa Elantak
- Structural Studies Division, MRC-Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, England, UK
| | | | | | | | | | | | | |
Collapse
|
48
|
Lumsden T, Bentley AA, Beutler W, Ghosh A, Galkin O, Komar AA. Yeast strains with N-terminally truncated ribosomal protein S5: implications for the evolution, structure and function of the Rps5/Rps7 proteins. Nucleic Acids Res 2009; 38:1261-72. [PMID: 19969550 PMCID: PMC2831326 DOI: 10.1093/nar/gkp1113] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Ribosomal protein (rp)S5 belongs to the family of the highly conserved rp's that contains rpS7 from prokaryotes and rpS5 from eukaryotes. Alignment of rpS5/rpS7 from metazoans (Homo sapiens), fungi (Saccharomyces cerevisiae) and bacteria (Escherichia coli) shows that the proteins contain a conserved central/C-terminal core region and possess variable N-terminal regions. Yeast rpS5 is 69 amino acids (aa) longer than the E. coli rpS7 protein; and human rpS5 is 48 aa longer than the rpS7, respectively. To investigate the function of the yeast rpS5 and in particular the role of its N-terminal region, we obtained and characterized yeast strains in which the wild-type yeast rpS5 was replaced by its truncated variants, lacking 13, 24, 30 and 46 N-terminal amino acids, respectively. All mutant yeast strains were viable and displayed only moderately reduced growth rates, with the exception of the strain lacking 46 N-terminal amino acids, which had a doubling time of about 3 h. Biochemical analysis of the mutant yeast strains suggests that the N-terminal part of the eukaryotic and, in particular, yeast rpS5 may impact the ability of 40S subunits to function properly in translation and affect the efficiency of initiation, specifically the recruitment of initiation factors eIF3 and eIF2.
Collapse
Affiliation(s)
- Thomas Lumsden
- Center for Gene Regulation in Health and Disease, Department of Biological, Geological and Environmental Sciences, Cleveland State University, 2121 Euclid Avenue, Cleveland, OH 44115, USA
| | | | | | | | | | | |
Collapse
|
49
|
Fraser CS. The molecular basis of translational control. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2009; 90:1-51. [PMID: 20374738 DOI: 10.1016/s1877-1173(09)90001-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Our current understanding of eukaryotic protein synthesis has emerged from many years of biochemical, genetic and biophysical approaches. Significant insight into the molecular details of the mechanism has been obtained, although there are clearly many aspects of the process that remain to be resolved. Importantly, our understanding of the mechanism has identified a number of key stages in the pathway that contribute to the regulation of general and gene-specific translation. Not surprisingly, translational control is now widely accepted to play a role in aspects of cell stress, growth, development, synaptic function, aging, and disease. This chapter reviews the mechanism of eukaryotic protein synthesis and its relevance to translational control.
Collapse
Affiliation(s)
- Christopher S Fraser
- Department of Molecular and Cellular Biology, University of California at Davis, Davis, California 95616, USA
| |
Collapse
|
50
|
Sha Z, Brill LM, Cabrera R, Kleifeld O, Scheliga JS, Glickman MH, Chang EC, Wolf DA. The eIF3 interactome reveals the translasome, a supercomplex linking protein synthesis and degradation machineries. Mol Cell 2009; 36:141-52. [PMID: 19818717 PMCID: PMC2789680 DOI: 10.1016/j.molcel.2009.09.026] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2009] [Revised: 06/23/2009] [Accepted: 09/11/2009] [Indexed: 01/18/2023]
Abstract
eIF3 promotes translation initiation, but relatively little is known about its full range of activities in the cell. Here, we employed affinity purification and highly sensitive LC-MS/MS to decipher the fission yeast eIF3 interactome, which was found to contain 230 proteins. eIF3 assembles into a large supercomplex, the translasome, which contains elongation factors, tRNA synthetases, 40S and 60S ribosomal proteins, chaperones, and the proteasome. eIF3 also associates with ribosome biogenesis factors and the importins-beta Kap123p and Sal3p. Our genetic data indicated that the binding to both importins-beta is essential for cell growth, and photobleaching experiments revealed a critical role for Sal3p in the nuclear import of one of the translasome constituents, the proteasome. Our data reveal the breadth of the eIF3 interactome and suggest that factors involved in translation initiation, ribosome biogenesis, translation elongation, quality control, and transport are physically linked to facilitate efficient protein synthesis.
Collapse
Affiliation(s)
- Zhe Sha
- 1 Baylor Plaza, Molecular and Cellular Biology Department, Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, TX 77030
| | - Laurence M. Brill
- Burnham Institute for Medical Research, Signal Transduction Program, NCI Cancer Center Proteomics Facility, 10901 North Torrey Pines Road, La Jolla, CA 92037
| | - Rodrigo Cabrera
- 1 Baylor Plaza, Molecular and Cellular Biology Department, Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, TX 77030
| | - Oded Kleifeld
- Department of Biology, Technion - Israel Institute of Technology, 32000 Haifa Israel
| | - Judith S. Scheliga
- Burnham Institute for Medical Research, Signal Transduction Program, NCI Cancer Center Proteomics Facility, 10901 North Torrey Pines Road, La Jolla, CA 92037
| | - Michael H. Glickman
- Department of Biology, Technion - Israel Institute of Technology, 32000 Haifa Israel
| | - Eric C. Chang
- 1 Baylor Plaza, Molecular and Cellular Biology Department, Lester and Sue Smith Breast Center, Baylor College of Medicine, Houston, TX 77030
| | - Dieter A. Wolf
- Burnham Institute for Medical Research, Signal Transduction Program, NCI Cancer Center Proteomics Facility, 10901 North Torrey Pines Road, La Jolla, CA 92037
| |
Collapse
|