1
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Villa N, Fraser CS. Human eukaryotic initiation factor 4G directly binds the 40S ribosomal subunit to promote efficient translation. J Biol Chem 2024; 300:107242. [PMID: 38569933 PMCID: PMC11063902 DOI: 10.1016/j.jbc.2024.107242] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2023] [Revised: 03/15/2024] [Accepted: 03/19/2024] [Indexed: 04/05/2024] Open
Abstract
Messenger RNA (mRNA) recruitment to the 40S ribosomal subunit is mediated by eukaryotic initiation factor 4F (eIF4F). This complex includes three subunits: eIF4E (m7G cap-binding protein), eIF4A (DEAD-box helicase), and eIF4G. Mammalian eIF4G is a scaffold that coordinates the activities of eIF4E and eIF4A and provides a bridge to connect the mRNA and 40S ribosomal subunit through its interaction with eIF3. While the roles of many eIF4G binding domains are relatively clear, the precise function of RNA binding by eIF4G remains to be elucidated. In this work, we used an eIF4G-dependent translation assay to reveal that the RNA binding domain (eIF4G-RBD; amino acids 682-720) stimulates translation. This stimulating activity is observed when eIF4G is independently tethered to an internal region of the mRNA, suggesting that the eIF4G-RBD promotes translation by a mechanism that is independent of the m7G cap and mRNA tethering. Using a kinetic helicase assay, we show that the eIF4G-RBD has a minimal effect on eIF4A helicase activity, demonstrating that the eIF4G-RBD is not required to coordinate eIF4F-dependent duplex unwinding. Unexpectedly, native gel electrophoresis and fluorescence polarization assays reveal a previously unidentified direct interaction between eIF4G and the 40S subunit. Using binding assays, our data show that this 40S subunit interaction is separate from the previously characterized interaction between eIF4G and eIF3. Thus, our work reveals how eIF4F can bind to the 40S subunit using eIF3-dependent and eIF3-independent binding domains to promote translation initiation.
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Affiliation(s)
- Nancy Villa
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, California, USA
| | - Christopher S Fraser
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, California, USA.
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2
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Brito Querido J, Díaz-López I, Ramakrishnan V. The molecular basis of translation initiation and its regulation in eukaryotes. Nat Rev Mol Cell Biol 2024; 25:168-186. [PMID: 38052923 DOI: 10.1038/s41580-023-00624-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/24/2023] [Indexed: 12/07/2023]
Abstract
The regulation of gene expression is fundamental for life. Whereas the role of transcriptional regulation of gene expression has been studied for several decades, it has been clear over the past two decades that post-transcriptional regulation of gene expression, of which translation regulation is a major part, can be equally important. Translation can be divided into four main stages: initiation, elongation, termination and ribosome recycling. Translation is controlled mainly during its initiation, a process which culminates in a ribosome positioned with an initiator tRNA over the start codon and, thus, ready to begin elongation of the protein chain. mRNA translation has emerged as a powerful tool for the development of innovative therapies, yet the detailed mechanisms underlying the complex process of initiation remain unclear. Recent studies in yeast and mammals have started to shed light on some previously unclear aspects of this process. In this Review, we discuss the current state of knowledge on eukaryotic translation initiation and its regulation in health and disease. Specifically, we focus on recent advances in understanding the processes involved in assembling the 43S pre-initiation complex and its recruitment by the cap-binding complex eukaryotic translation initiation factor 4F (eIF4F) at the 5' end of mRNA. In addition, we discuss recent insights into ribosome scanning along the 5' untranslated region of mRNA and selection of the start codon, which culminates in joining of the 60S large subunit and formation of the 80S initiation complex.
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Affiliation(s)
- Jailson Brito Querido
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK
- Department of Biological Chemistry, University of Michigan, Ann Arbor, MI, USA
- Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA
| | - Irene Díaz-López
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK
| | - V Ramakrishnan
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge, UK.
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3
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Jin M, Xie M, Dong L, Xue F, Li W, Jiang L, Li J, Zhang M, Song H, Lu Q, Yu Q. Exploration of Positive and Negative Schizophrenia Symptom Heterogeneity and Establishment of Symptom-Related miRNA-mRNA Regulatory Network: Based on Transcriptome Sequencing Data. Mol Neurobiol 2024:10.1007/s12035-024-03942-x. [PMID: 38267752 DOI: 10.1007/s12035-024-03942-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2023] [Accepted: 01/10/2024] [Indexed: 01/26/2024]
Abstract
Schizophrenia (SCZ) symptoms can be classified as positive and negative ones, each of which has distinct traits and possibly differences in gene expression and regulation. The co-expression networks linked to PANSS (Positive and Negative Syndrome Scale) scores were identified by weighted gene co-expression network analysis (WGCNA) using the expression profiles of miRNA and mRNA in the peripheral blood of first-episode SCZ patients. The heterogeneity between positive and negative symptoms was demonstrated using gene functional enrichment, gene-medication interaction, and immune cell composition analysis. Then, target gene prediction and correlation analysis of miRNA and mRNA constructed a symptom-related miRNA-mRNA regulatory network, screened regulatory pairs, and predicted binding sites. A total of six mRNA co-expression modules, two miRNA co-expression modules, and ten hub genes were screened to be significantly associated with positive symptoms; five mRNA co-expression modules and eight hub genes were correlated with negative symptoms. Positive symptom-related modules were significantly enriched in axon guidance, actin skeleton regulation, and sphingolipid signaling pathway, while negative symptom-related modules were significantly enriched in adaptive immune response, leukocyte migration, dopaminergic synapses, etc. The development of positive symptoms may have been influenced by potential regulatory pairings such as miR-98-5p-EIF3J, miR-98-5p-SOCS4, let-7b-5p-CLUH, miR-454-3p-GTF2H1, and let-7b-5p-SNX17. Additionally, immune cells were substantially connected with several hub genes for symptoms. Positive and negative symptoms in SCZ individuals were heterogeneous to some extent. miRNAs such as let-7b-5p and miR-98-5p might contribute to the incidence of positive symptoms by targeting mRNAs, while the immune system's role in developing negative symptoms may be more nuanced.
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Affiliation(s)
- Mengdi Jin
- Department of Epidemiology and Biostatistics, School of Public Health, Jilin University, 1163 Xinmin Street, Changchun, 130021, China
| | - Mengtong Xie
- Department of Epidemiology and Biostatistics, School of Public Health, Jilin University, 1163 Xinmin Street, Changchun, 130021, China
| | - Lin Dong
- Department of Epidemiology and Biostatistics, School of Public Health, Jilin University, 1163 Xinmin Street, Changchun, 130021, China
| | - Fengyu Xue
- Department of Epidemiology and Biostatistics, School of Public Health, Jilin University, 1163 Xinmin Street, Changchun, 130021, China
| | - Weizhen Li
- Department of Epidemiology and Biostatistics, School of Public Health, Jilin University, 1163 Xinmin Street, Changchun, 130021, China
| | - Lintong Jiang
- Department of Epidemiology and Biostatistics, School of Public Health, Jilin University, 1163 Xinmin Street, Changchun, 130021, China
| | - Junnan Li
- Department of Epidemiology and Biostatistics, School of Public Health, Jilin University, 1163 Xinmin Street, Changchun, 130021, China
| | - Min Zhang
- Department of Epidemiology and Biostatistics, School of Public Health, Jilin University, 1163 Xinmin Street, Changchun, 130021, China
| | - Haideng Song
- Department of Epidemiology and Biostatistics, School of Public Health, Jilin University, 1163 Xinmin Street, Changchun, 130021, China
| | - Qingxing Lu
- Department of Epidemiology and Biostatistics, School of Public Health, Jilin University, 1163 Xinmin Street, Changchun, 130021, China
| | - Qiong Yu
- Department of Epidemiology and Biostatistics, School of Public Health, Jilin University, 1163 Xinmin Street, Changchun, 130021, China.
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4
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Schubert K, Karousis ED, Ban I, Lapointe CP, Leibundgut M, Bäumlin E, Kummerant E, Scaiola A, Schönhut T, Ziegelmüller J, Puglisi JD, Mühlemann O, Ban N. Universal features of Nsp1-mediated translational shutdown by coronaviruses. Mol Cell 2023; 83:3546-3557.e8. [PMID: 37802027 PMCID: PMC10575594 DOI: 10.1016/j.molcel.2023.09.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Revised: 05/16/2023] [Accepted: 09/06/2023] [Indexed: 10/08/2023]
Abstract
Nonstructural protein 1 (Nsp1) produced by coronaviruses inhibits host protein synthesis. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Nsp1 C-terminal domain was shown to bind the ribosomal mRNA channel to inhibit translation, but it is unclear whether this mechanism is broadly used by coronaviruses, whether the Nsp1 N-terminal domain binds the ribosome, or how Nsp1 allows viral RNAs to be translated. Here, we investigated Nsp1 from SARS-CoV-2, Middle East respiratory syndrome coronavirus (MERS-CoV), and Bat-Hp-CoV coronaviruses using structural, biophysical, and biochemical experiments, revealing a conserved role for the C-terminal domain. Additionally, the N-terminal domain of Bat-Hp-CoV Nsp1 binds to the decoding center of the 40S subunit, where it would prevent mRNA and eIF1A accommodation. Structure-based experiments demonstrated the importance of decoding center interactions in all three coronaviruses and showed that the same regions of Nsp1 are necessary for the selective translation of viral RNAs. Our results provide a mechanistic framework to understand how Nsp1 controls preferential translation of viral RNAs.
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Affiliation(s)
- Katharina Schubert
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich 8049, Switzerland
| | - Evangelos D Karousis
- Department of Chemistry and Biochemistry, University of Bern, Bern 3012, Switzerland; Multidisciplinary Center for Infectious Diseases, University of Bern, Bern 3012, Switzerland.
| | - Ivo Ban
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich 8049, Switzerland
| | - Christopher P Lapointe
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Marc Leibundgut
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich 8049, Switzerland
| | - Emilie Bäumlin
- Department of Chemistry and Biochemistry, University of Bern, Bern 3012, Switzerland; Multidisciplinary Center for Infectious Diseases, University of Bern, Bern 3012, Switzerland
| | - Eric Kummerant
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich 8049, Switzerland
| | - Alain Scaiola
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich 8049, Switzerland
| | - Tanja Schönhut
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich 8049, Switzerland
| | - Jana Ziegelmüller
- Department of Chemistry and Biochemistry, University of Bern, Bern 3012, Switzerland
| | - Joseph D Puglisi
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA
| | - Oliver Mühlemann
- Department of Chemistry and Biochemistry, University of Bern, Bern 3012, Switzerland
| | - Nenad Ban
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich 8049, Switzerland.
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5
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Ochkasova A, Arbuzov G, Malygin A, Graifer D. Two "Edges" in Our Knowledge on the Functions of Ribosomal Proteins: The Revealed Contributions of Their Regions to Translation Mechanisms and the Issues of Their Extracellular Transport by Exosomes. Int J Mol Sci 2023; 24:11458. [PMID: 37511213 PMCID: PMC10380927 DOI: 10.3390/ijms241411458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2023] [Revised: 07/10/2023] [Accepted: 07/12/2023] [Indexed: 07/30/2023] Open
Abstract
Ribosomal proteins (RPs), the constituents of the ribosome, belong to the most abundant proteins in the cell. A highly coordinated network of interactions implicating RPs and ribosomal RNAs (rRNAs) forms the functionally competent structure of the ribosome, enabling it to perform translation, the synthesis of polypeptide chain on the messenger RNA (mRNA) template. Several RPs contact ribosomal ligands, namely, those with transfer RNAs (tRNAs), mRNA or translation factors in the course of translation, and the contribution of a number of these particular contacts to the translation process has recently been established. Many ribosomal proteins also have various extra-ribosomal functions unrelated to translation. The least-understood and -discussed functions of RPs are those related to their participation in the intercellular communication via extracellular vesicles including exosomes, etc., which often carry RPs as passengers. Recently reported data show that such a kind of communication can reprogram a receptor cell and change its phenotype, which is associated with cancer progression and metastasis. Here, we review the state-of-art ideas on the implications of specific amino acid residues of RPs in the particular stages of the translation process in higher eukaryotes and currently available data on the transport of RPs by extracellular vesicles and its biological effects.
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Affiliation(s)
- Anastasia Ochkasova
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia
| | - Grigory Arbuzov
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia
| | - Alexey Malygin
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia
| | - Dmitri Graifer
- Institute of Chemical Biology and Fundamental Medicine, Siberian Branch of the Russian Academy of Sciences, 630090 Novosibirsk, Russia
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6
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Schubert K, Karousis ED, Ban I, Lapointe CP, Leibundgut M, Bäumlin E, Kummerant E, Scaiola A, Schönhut T, Ziegelmüller J, Puglisi JD, Mühlemann O, Ban N. Universal features of Nsp1-mediated translational shutdown by coronaviruses. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.31.543022. [PMID: 37398176 PMCID: PMC10312502 DOI: 10.1101/2023.05.31.543022] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/04/2023]
Abstract
Nonstructural protein 1 (Nsp1) produced by coronaviruses shuts down host protein synthesis in infected cells. The C-terminal domain of SARS-CoV-2 Nsp1 was shown to bind to the small ribosomal subunit to inhibit translation, but it is not clear whether this mechanism is broadly used by coronaviruses, whether the N-terminal domain of Nsp1 binds the ribosome, or how Nsp1 specifically permits translation of viral mRNAs. Here, we investigated Nsp1 from three representative Betacoronaviruses - SARS-CoV-2, MERS-CoV, and Bat-Hp-CoV - using structural, biophysical, and biochemical assays. We revealed a conserved mechanism of host translational shutdown across the three coronaviruses. We further demonstrated that the N-terminal domain of Bat-Hp-CoV Nsp1 binds to the decoding center of the 40S subunit, where it would prevent mRNA and eIF1A binding. Structure-based biochemical experiments identified a conserved role of these inhibitory interactions in all three coronaviruses and showed that the same regions of Nsp1 are responsible for the preferential translation of viral mRNAs. Our results provide a mechanistic framework to understand how Betacoronaviruses overcome translational inhibition to produce viral proteins.
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Affiliation(s)
- Katharina Schubert
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
| | - Evangelos D Karousis
- Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland
- Multidisciplinary Center for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Ivo Ban
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
| | - Christopher P Lapointe
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Marc Leibundgut
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
| | - Emilie Bäumlin
- Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland
- Multidisciplinary Center for Infectious Diseases, University of Bern, Bern, Switzerland
| | - Eric Kummerant
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
| | - Alain Scaiola
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
| | - Tanja Schönhut
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
| | - Jana Ziegelmüller
- Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland
| | - Joseph D Puglisi
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Oliver Mühlemann
- Department of Chemistry and Biochemistry, University of Bern, Bern, Switzerland
| | - Nenad Ban
- Department of Biology, Institute of Molecular Biology and Biophysics, ETH Zurich, Zurich, Switzerland
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7
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Zhang D, Zhu L, Wang F, Li P, Wang Y, Gao Y. Molecular mechanisms of eukaryotic translation fidelity and their associations with diseases. Int J Biol Macromol 2023; 242:124680. [PMID: 37141965 DOI: 10.1016/j.ijbiomac.2023.124680] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2023] [Accepted: 04/27/2023] [Indexed: 05/06/2023]
Abstract
Converting genetic information into functional proteins is a complex, multi-step process, with each step being tightly regulated to ensure the accuracy of translation, which is critical to cellular health. In recent years, advances in modern biotechnology, especially the development of cryo-electron microscopy and single-molecule techniques, have enabled a clearer understanding of the mechanisms of protein translation fidelity. Although there are many studies on the regulation of protein translation in prokaryotes, and the basic elements of translation are highly conserved in prokaryotes and eukaryotes, there are still great differences in the specific regulatory mechanisms. This review describes how eukaryotic ribosomes and translation factors regulate protein translation and ensure translation accuracy. However, a certain frequency of translation errors does occur in translation, so we describe diseases that arise when the rate of translation errors reaches or exceeds a threshold of cellular tolerance.
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Affiliation(s)
- Dejiu Zhang
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao, China
| | - Lei Zhu
- College of Basic Medical, Qingdao Binhai University, Qingdao, China
| | - Fei Wang
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao, China
| | - Peifeng Li
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao, China
| | - Yin Wang
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao, China.
| | - Yanyan Gao
- Institute for Translational Medicine, The Affiliated Hospital of Qingdao University, College of Medicine, Qingdao University, Qingdao, China.
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8
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Hartenian E, Mendez AS, Didychuk AL, Khosla S, Glaunsinger B. DNA processing by the Kaposi's sarcoma-associated herpesvirus alkaline exonuclease SOX contributes to viral gene expression and infectious virion production. Nucleic Acids Res 2022; 51:182-197. [PMID: 36537232 PMCID: PMC9841436 DOI: 10.1093/nar/gkac1190] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Revised: 11/22/2022] [Accepted: 11/29/2022] [Indexed: 12/24/2022] Open
Abstract
Alkaline exonucleases (AE) are present in several large DNA viruses including bacteriophage λ and herpesviruses, where they play roles in viral DNA processing during genome replication. Given the genetic conservation of AEs across viruses infecting different kingdoms of life, these enzymes likely assume central roles in the lifecycles of viruses where they have yet to be well characterized. Here, we applied a structure-guided functional analysis of the bifunctional AE in the oncogenic human gammaherpesvirus Kaposi's sarcoma-associated herpesvirus (KSHV), called SOX. In addition to identifying a preferred DNA substrate preference for SOX, we define key residues important for DNA binding and DNA processing, and how SOX activity on DNA partially overlaps with its functionally separable cleavage of mRNA. By engineering these SOX mutants into KSHV, we reveal roles for its DNase activity in viral gene expression and infectious virion production. Our results provide mechanistic insight into gammaherpesviral AE activity as well as areas of functional conservation between this mammalian virus AE and its distant relative in phage λ.
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Affiliation(s)
| | - Aaron S Mendez
- Correspondence may also be addressed to Aaron S. Mendez.
| | - Allison L Didychuk
- Department of Plant and Microbial Biology, University of California Berkeley, CA 94720, USA,Department of Molecular Biophysics & Biochemistry, Yale University, New Haven, CT 06511, USA
| | - Shivani Khosla
- Department of Molecular and Cell Biology, University of California Berkeley, CA 94720, USA
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9
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Song Z, Lin J, Su R, Ji Y, Jia R, Li S, Shan G, Huang C. eIF3j inhibits translation of a subset of circular RNAs in eukaryotic cells. Nucleic Acids Res 2022; 50:11529-11549. [PMID: 36330957 PMCID: PMC9723666 DOI: 10.1093/nar/gkac980] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Revised: 10/04/2022] [Accepted: 10/17/2022] [Indexed: 11/06/2022] Open
Abstract
Increasing studies have revealed that a subset of circular RNAs (circRNAs) harbor an open reading frame and can act as protein-coding templates to generate functional proteins that are closely associated with multiple physiological and disease-relevant processes, and thus proper regulation of synthesis of these circRNA-derived proteins is a fundamental cellular process required for homeostasis maintenance. However, how circRNA translation initiation is coordinated by different trans-acting factors remains poorly understood. In particular, the impact of different eukaryotic translation initiation factors (eIFs) on circRNA translation and the physiological relevance of this distinct regulation have not yet been characterized. In this study, we screened all 43 Drosophila eIFs and revealed the conflicting functions of eIF3 subunits in the translational control of the translatable circRNA circSfl: eIF3 is indispensable for circSfl translation, while the eIF3-associated factor eIF3j is the most potent inhibitor. Mechanistically, the binding of eIF3j to circSfl promotes the disassociation of eIF3. The C-terminus of eIF3j and an RNA regulon within the circSfl untranslated region (UTR) are essential for the inhibitory effect of eIF3j. Moreover, we revealed the physiological relevance of eIF3j-mediated circSfl translation repression in response to heat shock. Finally, additional translatable circRNAs were identified to be similarly regulated in an eIF3j-dependent manner. Altogether, our study provides a significant insight into the field of cap-independent translational regulation and undiscovered functions of eIF3.
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Affiliation(s)
| | | | - Rui Su
- School of Life Sciences, Chongqing University, Chongqing 401331, China
| | - Yu Ji
- School of Life Sciences, Chongqing University, Chongqing 401331, China
| | - Ruirui Jia
- School of Life Sciences, Chongqing University, Chongqing 401331, China
| | - Shi Li
- School of Life Sciences, Chongqing University, Chongqing 401331, China
| | - Ge Shan
- School of Basic Medical Sciences, Division of Life Science and Medicine, University of Science and Technology of China, Hefei 230027, China
| | - Chuan Huang
- To whom correspondence should be addressed. Tel: +86 19956025374;
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10
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Lapointe CP, Grosely R, Sokabe M, Alvarado C, Wang J, Montabana E, Villa N, Shin BS, Dever TE, Fraser CS, Fernández IS, Puglisi JD. eIF5B and eIF1A reorient initiator tRNA to allow ribosomal subunit joining. Nature 2022; 607:185-190. [PMID: 35732735 PMCID: PMC9728550 DOI: 10.1038/s41586-022-04858-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2021] [Accepted: 05/11/2022] [Indexed: 01/03/2023]
Abstract
Translation initiation defines the identity and quantity of a synthesized protein. The process is dysregulated in many human diseases1,2. A key commitment step is when the ribosomal subunits join at a translation start site on a messenger RNA to form a functional ribosome. Here, we combined single-molecule spectroscopy and structural methods using an in vitro reconstituted system to examine how the human ribosomal subunits join. Single-molecule fluorescence revealed when the universally conserved eukaryotic initiation factors eIF1A and eIF5B associate with and depart from initiation complexes. Guided by single-molecule dynamics, we visualized initiation complexes that contained both eIF1A and eIF5B using single-particle cryo-electron microscopy. The resulting structure revealed how eukaryote-specific contacts between the two proteins remodel the initiation complex to orient the initiator aminoacyl-tRNA in a conformation compatible with ribosomal subunit joining. Collectively, our findings provide a quantitative and architectural framework for the molecular choreography orchestrated by eIF1A and eIF5B during translation initiation in humans.
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Affiliation(s)
- Christopher P Lapointe
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Rosslyn Grosely
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Masaaki Sokabe
- Department of Molecular and Cellular Biology College of Biological Sciences, University of California, Davis, CA, USA
| | - Carlos Alvarado
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Jinfan Wang
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Elizabeth Montabana
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA
| | - Nancy Villa
- Department of Molecular and Cellular Biology College of Biological Sciences, University of California, Davis, CA, USA
| | - Byung-Sik Shin
- Section on Protein Biosynthesis, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Thomas E Dever
- Section on Protein Biosynthesis, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Christopher S Fraser
- Department of Molecular and Cellular Biology College of Biological Sciences, University of California, Davis, CA, USA
| | - Israel S Fernández
- Department of Structural Biology, St Jude Children's Research Hospital, Memphis, TN, USA.
| | - Joseph D Puglisi
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA, USA.
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11
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Yi SH, Petrychenko V, Schliep JE, Goyal A, Linden A, Chari A, Urlaub H, Stark H, Rodnina MV, Adio S, Fischer N. Conformational rearrangements upon start codon recognition in human 48S translation initiation complex. Nucleic Acids Res 2022; 50:5282-5298. [PMID: 35489072 PMCID: PMC9122606 DOI: 10.1093/nar/gkac283] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Revised: 04/08/2022] [Accepted: 04/20/2022] [Indexed: 01/10/2023] Open
Abstract
Selection of the translation start codon is a key step during protein synthesis in human cells. We obtained cryo-EM structures of human 48S initiation complexes and characterized the intermediates of codon recognition by kinetic methods using eIF1A as a reporter. Both approaches capture two distinct ribosome populations formed on an mRNA with a cognate AUG codon in the presence of eIF1, eIF1A, eIF2–GTP–Met-tRNAiMet and eIF3. The ‘open’ 40S subunit conformation differs from the human 48S scanning complex and represents an intermediate preceding the codon recognition step. The ‘closed’ form is similar to reported structures of complexes from yeast and mammals formed upon codon recognition, except for the orientation of eIF1A, which is unique in our structure. Kinetic experiments show how various initiation factors mediate the population distribution of open and closed conformations until 60S subunit docking. Our results provide insights into the timing and structure of human translation initiation intermediates and suggest the differences in the mechanisms of start codon selection between mammals and yeast.
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Affiliation(s)
- Sung-Hui Yi
- Department of Physical Biochemistry, Max Planck Institute for Multidisciplinary Sciences, Göttingen 37077, Germany
| | - Valentyn Petrychenko
- Department of Structural Dynamics, Max Planck Institute for Multidisciplinary Sciences, Göttingen 37077, Germany
| | - Jan Erik Schliep
- Department of Structural Dynamics, Max Planck Institute for Multidisciplinary Sciences, Göttingen 37077, Germany
| | - Akanksha Goyal
- Department of Physical Biochemistry, Max Planck Institute for Multidisciplinary Sciences, Göttingen 37077, Germany
| | - Andreas Linden
- Bioanalytical Mass Spectroscopy Group, Max Planck Institute for Multidisciplinary Sciences, Göttingen 37077, Germany.,Bioanalytics, Institute for Clinical Chemistry, University Medical Center Göttingen, Göttingen 37075, Germany
| | - Ashwin Chari
- Research Group Structural Biochemistry and Mechanisms, Max Planck Institute for Multidisciplinary Sciences, Göttingen 37077, Germany
| | - Henning Urlaub
- Bioanalytical Mass Spectroscopy Group, Max Planck Institute for Multidisciplinary Sciences, Göttingen 37077, Germany.,Bioanalytics, Institute for Clinical Chemistry, University Medical Center Göttingen, Göttingen 37075, Germany
| | - Holger Stark
- Department of Structural Dynamics, Max Planck Institute for Multidisciplinary Sciences, Göttingen 37077, Germany
| | - Marina V Rodnina
- Department of Physical Biochemistry, Max Planck Institute for Multidisciplinary Sciences, Göttingen 37077, Germany
| | - Sarah Adio
- Department of Molecular Structural Biology, Institute for Microbiology and Genetics, Georg-August University of Göttingen, Göttingen 37077, Germany
| | - Niels Fischer
- Department of Structural Dynamics, Max Planck Institute for Multidisciplinary Sciences, Göttingen 37077, Germany
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12
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Young DJ, Guydosh NR. Rebirth of the translational machinery: The importance of recycling ribosomes. Bioessays 2022; 44:e2100269. [PMID: 35147231 PMCID: PMC9270684 DOI: 10.1002/bies.202100269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2021] [Revised: 01/26/2022] [Accepted: 01/27/2022] [Indexed: 11/10/2022]
Abstract
Translation of the genetic code occurs in a cycle where ribosomes engage mRNAs, synthesize protein, and then disengage in order to repeat the process again. The final part of this process-ribosome recycling, where ribosomes dissociate from mRNAs-involves a complex molecular choreography of specific protein factors to remove the large and small subunits of the ribosome in a coordinated fashion. Errors in this process can lead to the accumulation of ribosomes at stop codons or translation of downstream open reading frames (ORFs). Ribosome recycling is also critical when a ribosome stalls during the elongation phase of translation and must be rescued to allow continued translation of the mRNA. Here we discuss the molecular interactions that drive ribosome recycling, and their regulation in the cell. We also examine the consequences of inefficient recycling with regards to disease, and its functional roles in synthesis of novel peptides, regulation of gene expression, and control of mRNA-associated proteins. Alterations in ribosome recycling efficiency have the potential to impact many cellular functions but additional work is needed to understand how this regulatory power is utilized.
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Affiliation(s)
- David J Young
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA
| | - Nicholas R Guydosh
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland, USA
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13
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Egorova T, Biziaev N, Shuvalov A, Sokolova E, Mukba S, Evmenov K, Zotova M, Kushchenko A, Shuvalova E, Alkalaeva E. eIF3j facilitates loading of release factors into the ribosome. Nucleic Acids Res 2021; 49:11181-11196. [PMID: 34591963 PMCID: PMC8565342 DOI: 10.1093/nar/gkab854] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2021] [Revised: 08/23/2021] [Accepted: 09/14/2021] [Indexed: 12/14/2022] Open
Abstract
eIF3j is one of the eukaryotic translation factors originally reported as the labile subunit of the eukaryotic translation initiation factor eIF3. The yeast homolog of this protein, Hcr1, has been implicated in stringent AUG recognition as well as in controlling translation termination and stop codon readthrough. Using a reconstituted mammalian in vitro translation system, we showed that the human protein eIF3j is also important for translation termination. We showed that eIF3j stimulates peptidyl-tRNA hydrolysis induced by a complex of eukaryotic release factors, eRF1-eRF3. Moreover, in combination with the initiation factor eIF3, which also stimulates peptide release, eIF3j activity in translation termination increases. We found that eIF3j interacts with the pre-termination ribosomal complex, and eRF3 destabilises this interaction. In the solution, these proteins bind to each other and to other participants of translation termination, eRF1 and PABP, in the presence of GTP. Using a toe-printing assay, we determined the stage at which eIF3j functions – binding of release factors to the A-site of the ribosome before GTP hydrolysis. Based on these data, we assumed that human eIF3j is involved in the regulation of translation termination by loading release factors into the ribosome.
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Affiliation(s)
- Tatiana Egorova
- Engelhardt Institute of Molecular Biology, the Russian Academy of Sciences, 119991 Moscow, Russia.,Center for Precision Genome Editing and Genetic Technologies for Biomedicine, 119991 Moscow, Russia
| | - Nikita Biziaev
- Engelhardt Institute of Molecular Biology, the Russian Academy of Sciences, 119991 Moscow, Russia
| | - Alexey Shuvalov
- Engelhardt Institute of Molecular Biology, the Russian Academy of Sciences, 119991 Moscow, Russia.,Center for Precision Genome Editing and Genetic Technologies for Biomedicine, 119991 Moscow, Russia
| | - Elizaveta Sokolova
- Engelhardt Institute of Molecular Biology, the Russian Academy of Sciences, 119991 Moscow, Russia.,Center for Precision Genome Editing and Genetic Technologies for Biomedicine, 119991 Moscow, Russia
| | - Sabina Mukba
- Engelhardt Institute of Molecular Biology, the Russian Academy of Sciences, 119991 Moscow, Russia
| | - Konstantin Evmenov
- Engelhardt Institute of Molecular Biology, the Russian Academy of Sciences, 119991 Moscow, Russia
| | - Maria Zotova
- Engelhardt Institute of Molecular Biology, the Russian Academy of Sciences, 119991 Moscow, Russia
| | - Artem Kushchenko
- Engelhardt Institute of Molecular Biology, the Russian Academy of Sciences, 119991 Moscow, Russia
| | - Ekaterina Shuvalova
- Engelhardt Institute of Molecular Biology, the Russian Academy of Sciences, 119991 Moscow, Russia
| | - Elena Alkalaeva
- Engelhardt Institute of Molecular Biology, the Russian Academy of Sciences, 119991 Moscow, Russia.,Center for Precision Genome Editing and Genetic Technologies for Biomedicine, 119991 Moscow, Russia
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14
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Mendez AS, Ly M, González-Sánchez AM, Hartenian E, Ingolia NT, Cate JH, Glaunsinger BA. The N-terminal domain of SARS-CoV-2 nsp1 plays key roles in suppression of cellular gene expression and preservation of viral gene expression. Cell Rep 2021; 37:109841. [PMID: 34624207 PMCID: PMC8481097 DOI: 10.1016/j.celrep.2021.109841] [Citation(s) in RCA: 60] [Impact Index Per Article: 20.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2021] [Revised: 08/16/2021] [Accepted: 09/24/2021] [Indexed: 01/23/2023] Open
Abstract
Nonstructural protein 1 (nsp1) is a coronavirus (CoV) virulence factor that restricts cellular gene expression by inhibiting translation through blocking the mRNA entry channel of the 40S ribosomal subunit and by promoting mRNA degradation. We perform a detailed structure-guided mutational analysis of severe acute respiratory syndrome (SARS)-CoV-2 nsp1, revealing insights into how it coordinates these activities against host but not viral mRNA. We find that residues in the N-terminal and central regions of nsp1 not involved in docking into the 40S mRNA entry channel nonetheless stabilize its association with the ribosome and mRNA, both enhancing its restriction of host gene expression and enabling mRNA containing the SARS-CoV-2 leader sequence to escape translational repression. These data support a model in which viral mRNA binding functionally alters the association of nsp1 with the ribosome, which has implications for drug targeting and understanding how engineered or emerging mutations in SARS-CoV-2 nsp1 could attenuate the virus.
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Affiliation(s)
- Aaron S Mendez
- Department of Plant & Microbial Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Michael Ly
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Angélica M González-Sánchez
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA; Comparative Biochemistry Graduate Program, University of California, Berkeley, Berkeley, CA, USA
| | - Ella Hartenian
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA
| | - Nicholas T Ingolia
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA; California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA, USA
| | - Jamie H Cate
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA; California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA, USA; Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA, USA; Department of Chemistry, University of California, Berkeley, Berkeley, CA, USA; Molecular Biophysics & Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA
| | - Britt A Glaunsinger
- Department of Plant & Microbial Biology, University of California, Berkeley, Berkeley, CA, USA; Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA, USA; California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, CA, USA; Innovative Genomics Institute, University of California, Berkeley, Berkeley, CA, USA; Howard Hughes Medical Institute, Berkeley, CA, USA.
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15
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Yuan S, Balaji S, Lomakin IB, Xiong Y. Coronavirus Nsp1: Immune Response Suppression and Protein Expression Inhibition. Front Microbiol 2021; 12:752214. [PMID: 34659188 PMCID: PMC8512706 DOI: 10.3389/fmicb.2021.752214] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2021] [Accepted: 08/24/2021] [Indexed: 12/30/2022] Open
Abstract
Coronaviruses have brought severe challenges to public health all over the world in the past 20years. SARS-CoV-2, the causative agent of the COVID-19 pandemic that has led to millions of deaths, belongs to the genus beta-coronavirus. Alpha- and beta-coronaviruses encode a unique protein, nonstructural protein 1 (Nsp1) that both suppresses host immune responses and reduces global gene expression levels in the host cells. As a key pathogenicity factor of coronaviruses, Nsp1 redirects the host translation machinery to increase synthesis of viral proteins. Through multiple mechanisms, coronaviruses impede host protein expression through Nsp1, while escaping inhibition to allow the translation of viral RNA. In this review, we discuss current data about suppression of the immune responses and inhibition of protein synthesis induced by coronavirus Nsp1, as well as the prospect of live-attenuated vaccine development with virulence-attenuated viruses with mutations in Nsp1.
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Affiliation(s)
- Shuai Yuan
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, United States
| | - Shravani Balaji
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, United States
| | - Ivan B Lomakin
- Department of Dermatology, Yale University School of Medicine, New Haven, CT, United States
| | - Yong Xiong
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT, United States
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16
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Alghoul F, Laure S, Eriani G, Martin F. Translation inhibitory elements from Hoxa3 and Hoxa11 mRNAs use uORFs for translation inhibition. eLife 2021; 10:e66369. [PMID: 34076576 PMCID: PMC8172242 DOI: 10.7554/elife.66369] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Accepted: 05/20/2021] [Indexed: 01/20/2023] Open
Abstract
During embryogenesis, Hox mRNA translation is tightly regulated by a sophisticated molecular mechanism that combines two RNA regulons located in their 5'UTR. First, an internal ribosome entry site (IRES) enables cap-independent translation. The second regulon is a translation inhibitory element or TIE, which ensures concomitant cap-dependent translation inhibition. In this study, we deciphered the molecular mechanisms of mouse Hoxa3 and Hoxa11 TIEs. Both TIEs possess an upstream open reading frame (uORF) that is critical to inhibit cap-dependent translation. However, the molecular mechanisms used are different. In Hoxa3 TIE, we identify an uORF which inhibits cap-dependent translation and we show the requirement of the non-canonical initiation factor eIF2D for this process. The mode of action of Hoxa11 TIE is different, it also contains an uORF but it is a minimal uORF formed by an uAUG followed immediately by a stop codon, namely a 'start-stop'. The 'start-stop' sequence is species-specific and in mice, is located upstream of a highly stable stem loop structure which stalls the 80S ribosome and thereby inhibits cap-dependent translation of Hoxa11 main ORF.
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Affiliation(s)
- Fatima Alghoul
- Institut de Biologie Moléculaire et Cellulaire, “Architecture et Réactivité de l’ARN” CNRS UPR9002, Université de StrasbourgStrasbourgFrance
| | - Schaeffer Laure
- Institut de Biologie Moléculaire et Cellulaire, “Architecture et Réactivité de l’ARN” CNRS UPR9002, Université de StrasbourgStrasbourgFrance
| | - Gilbert Eriani
- Institut de Biologie Moléculaire et Cellulaire, “Architecture et Réactivité de l’ARN” CNRS UPR9002, Université de StrasbourgStrasbourgFrance
| | - Franck Martin
- Institut de Biologie Moléculaire et Cellulaire, “Architecture et Réactivité de l’ARN” CNRS UPR9002, Université de StrasbourgStrasbourgFrance
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17
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Singh K, Lin J, Lecomte N, Mohan P, Gokce A, Sanghvi VR, Jiang M, Grbovic-Huezo O, Burčul A, Stark SG, Romesser PB, Chang Q, Melchor JP, Beyer RK, Duggan M, Fukase Y, Yang G, Ouerfelli O, Viale A, de Stanchina E, Stamford AW, Meinke PT, Rätsch G, Leach SD, Ouyang Z, Wendel HG. Targeting eIF4A-Dependent Translation of KRAS Signaling Molecules. Cancer Res 2021; 81:2002-2014. [PMID: 33632898 PMCID: PMC8137674 DOI: 10.1158/0008-5472.can-20-2929] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2020] [Revised: 12/01/2020] [Accepted: 02/22/2021] [Indexed: 11/16/2022]
Abstract
Pancreatic adenocarcinoma (PDAC) epitomizes a deadly cancer driven by abnormal KRAS signaling. Here, we show that the eIF4A RNA helicase is required for translation of key KRAS signaling molecules and that pharmacological inhibition of eIF4A has single-agent activity against murine and human PDAC models at safe dose levels. EIF4A was uniquely required for the translation of mRNAs with long and highly structured 5' untranslated regions, including those with multiple G-quadruplex elements. Computational analyses identified these features in mRNAs encoding KRAS and key downstream molecules. Transcriptome-scale ribosome footprinting accurately identified eIF4A-dependent mRNAs in PDAC, including critical KRAS signaling molecules such as PI3K, RALA, RAC2, MET, MYC, and YAP1. These findings contrast with a recent study that relied on an older method, polysome fractionation, and implicated redox-related genes as eIF4A clients. Together, our findings highlight the power of ribosome footprinting in conjunction with deep RNA sequencing in accurately decoding translational control mechanisms and define the therapeutic mechanism of eIF4A inhibitors in PDAC. SIGNIFICANCE: These findings document the coordinate, eIF4A-dependent translation of RAS-related oncogenic signaling molecules and demonstrate therapeutic efficacy of eIF4A blockade in pancreatic adenocarcinoma.
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Affiliation(s)
- Kamini Singh
- Cancer Biology and Genetics Program, Memorial Sloan-Kettering Cancer Center, New York, New York
| | - Jianan Lin
- The Jackson Laboratory for Genomic Medicine, Farmington, Connecticut
- Department of Biomedical Engineering, University of Connecticut, Storrs, Connecticut
| | - Nicolas Lecomte
- David M. Rubenstein Center for Pancreatic Cancer Research, Memorial Sloan-Kettering Cancer Center, New York, New York
| | - Prathibha Mohan
- Cancer Biology and Genetics Program, Memorial Sloan-Kettering Cancer Center, New York, New York
| | - Askan Gokce
- David M. Rubenstein Center for Pancreatic Cancer Research, Memorial Sloan-Kettering Cancer Center, New York, New York
| | - Viraj R Sanghvi
- Cancer Biology and Genetics Program, Memorial Sloan-Kettering Cancer Center, New York, New York
- Department of Molecular and Cellular Pharmacology, Sylvester Comprehensive Cancer Center, Miller School of Medicine, University of Miami, Miami, Florida
| | - Man Jiang
- Cancer Biology and Genetics Program, Memorial Sloan-Kettering Cancer Center, New York, New York
| | - Olivera Grbovic-Huezo
- Cancer Biology and Genetics Program, Memorial Sloan-Kettering Cancer Center, New York, New York
| | - Antonija Burčul
- Computational Biology Department, Memorial Sloan-Kettering Cancer Center, New York, New York
| | - Stefan G Stark
- Computational Biology Department, Memorial Sloan-Kettering Cancer Center, New York, New York
- Department of Computer Science, Biomedical Informatics, ETH, Zürich, Zürich, Switzerland
| | - Paul B Romesser
- Department of Radiation Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York
| | - Qing Chang
- Molecular Pharmacology Program, Memorial Sloan-Kettering Cancer Center, New York, New York
| | - Jerry P Melchor
- David M. Rubenstein Center for Pancreatic Cancer Research, Memorial Sloan-Kettering Cancer Center, New York, New York
| | - Rachel K Beyer
- Cancer Research Technology Program, Frederick National Laboratory for Cancer Research, Frederick, Maryland
| | - Mark Duggan
- Tri-Institutional Drug Development Initiative, Memorial Sloan-Kettering Cancer Center, New York, New York
| | - Yoshiyuki Fukase
- Tri-Institutional Drug Development Initiative, Memorial Sloan-Kettering Cancer Center, New York, New York
| | - Guangli Yang
- The Organic Synthesis Core Facility, Memorial Sloan-Kettering Cancer Center, New York, New York
| | - Ouathek Ouerfelli
- The Organic Synthesis Core Facility, Memorial Sloan-Kettering Cancer Center, New York, New York
| | - Agnes Viale
- Integrated Genomics Operation, Center for Molecular Oncology, Memorial Sloan-Kettering Cancer Center, New York, New York
| | - Elisa de Stanchina
- Molecular Pharmacology Program, Memorial Sloan-Kettering Cancer Center, New York, New York
| | - Andrew W Stamford
- Tri-Institutional Drug Development Initiative, Memorial Sloan-Kettering Cancer Center, New York, New York
| | - Peter T Meinke
- Tri-Institutional Drug Development Initiative, Memorial Sloan-Kettering Cancer Center, New York, New York
| | - Gunnar Rätsch
- Computational Biology Department, Memorial Sloan-Kettering Cancer Center, New York, New York
- Department of Computer Science, Biomedical Informatics, ETH, Zürich, Zürich, Switzerland
| | - Steven D Leach
- Molecular Systems Biology and Surgery, Geisel School of Medicine, Dartmouth, Norris Cotton Cancer Center at Dartmouth-Hitchcock, Lebanon, New Hampshire
| | - Zhengqing Ouyang
- Department of Biostatistics and Epidemiology, School of Public Health and Health Sciences, University of Massachusetts, Amherst, Massachusetts
| | - Hans-Guido Wendel
- Cancer Biology and Genetics Program, Memorial Sloan-Kettering Cancer Center, New York, New York.
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18
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Lapointe CP, Grosely R, Johnson AG, Wang J, Fernández IS, Puglisi JD. Dynamic competition between SARS-CoV-2 NSP1 and mRNA on the human ribosome inhibits translation initiation. Proc Natl Acad Sci U S A 2021; 118:e2017715118. [PMID: 33479166 PMCID: PMC8017934 DOI: 10.1073/pnas.2017715118] [Citation(s) in RCA: 114] [Impact Index Per Article: 38.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a beta-CoV that recently emerged as a human pathogen and is the causative agent of the COVID-19 pandemic. A molecular framework of how the virus manipulates host cellular machinery to facilitate infection remains unclear. Here, we focus on SARS-CoV-2 NSP1, which is proposed to be a virulence factor that inhibits protein synthesis by directly binding the human ribosome. We demonstrate biochemically that NSP1 inhibits translation of model human and SARS-CoV-2 messenger RNAs (mRNAs). NSP1 specifically binds to the small (40S) ribosomal subunit, which is required for translation inhibition. Using single-molecule fluorescence assays to monitor NSP1-40S subunit binding in real time, we determine that eukaryotic translation initiation factors (eIFs) allosterically modulate the interaction of NSP1 with ribosomal preinitiation complexes in the absence of mRNA. We further elucidate that NSP1 competes with RNA segments downstream of the start codon to bind the 40S subunit and that the protein is unable to associate rapidly with 80S ribosomes assembled on an mRNA. Collectively, our findings support a model where NSP1 proteins from viruses in at least two subgenera of beta-CoVs associate with the open head conformation of the 40S subunit to inhibit an early step of translation, by preventing accommodation of mRNA within the entry channel.
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Affiliation(s)
- Christopher P Lapointe
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305
| | - Rosslyn Grosely
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305
| | - Alex G Johnson
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305
| | - Jinfan Wang
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305
| | - Israel S Fernández
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York City, NY 10032
| | - Joseph D Puglisi
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305;
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19
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Lapointe CP, Grosely R, Johnson AG, Wang J, Fernández IS, Puglisi JD. Dynamic competition between SARS-CoV-2 NSP1 and mRNA on the human ribosome inhibits translation initiation. Proc Natl Acad Sci U S A 2021. [PMID: 33479166 DOI: 10.1101/2020.08.20.259770] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/13/2023] Open
Abstract
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a beta-CoV that recently emerged as a human pathogen and is the causative agent of the COVID-19 pandemic. A molecular framework of how the virus manipulates host cellular machinery to facilitate infection remains unclear. Here, we focus on SARS-CoV-2 NSP1, which is proposed to be a virulence factor that inhibits protein synthesis by directly binding the human ribosome. We demonstrate biochemically that NSP1 inhibits translation of model human and SARS-CoV-2 messenger RNAs (mRNAs). NSP1 specifically binds to the small (40S) ribosomal subunit, which is required for translation inhibition. Using single-molecule fluorescence assays to monitor NSP1-40S subunit binding in real time, we determine that eukaryotic translation initiation factors (eIFs) allosterically modulate the interaction of NSP1 with ribosomal preinitiation complexes in the absence of mRNA. We further elucidate that NSP1 competes with RNA segments downstream of the start codon to bind the 40S subunit and that the protein is unable to associate rapidly with 80S ribosomes assembled on an mRNA. Collectively, our findings support a model where NSP1 proteins from viruses in at least two subgenera of beta-CoVs associate with the open head conformation of the 40S subunit to inhibit an early step of translation, by preventing accommodation of mRNA within the entry channel.
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Affiliation(s)
- Christopher P Lapointe
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305
| | - Rosslyn Grosely
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305
| | - Alex G Johnson
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, CA 94305
| | - Jinfan Wang
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305
| | - Israel S Fernández
- Department of Biochemistry and Molecular Biophysics, Columbia University, New York City, NY 10032
| | - Joseph D Puglisi
- Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305;
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20
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Cai YD, Xue Y, Truong CC, Del Carmen-Li J, Ochoa C, Vanselow JT, Murphy KA, Li YH, Liu X, Kunimoto BL, Zheng H, Zhao C, Zhang Y, Schlosser A, Chiu JC. CK2 Inhibits TIMELESS Nuclear Export and Modulates CLOCK Transcriptional Activity to Regulate Circadian Rhythms. Curr Biol 2021; 31:502-514.e7. [PMID: 33217322 PMCID: PMC7878342 DOI: 10.1016/j.cub.2020.10.061] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2020] [Revised: 09/25/2020] [Accepted: 10/20/2020] [Indexed: 11/06/2022]
Abstract
Circadian clocks orchestrate daily rhythms in organismal physiology and behavior to promote optimal performance and fitness. In Drosophila, key pacemaker proteins PERIOD (PER) and TIMELESS (TIM) are progressively phosphorylated to perform phase-specific functions. Whereas PER phosphorylation has been extensively studied, systematic analysis of site-specific TIM phosphorylation is lacking. Here, we identified phosphorylation sites of PER-bound TIM by mass spectrometry, given the importance of TIM as a modulator of PER function in the pacemaker. Among the 12 TIM phosphorylation sites we identified, at least two of them are critical for circadian timekeeping as mutants expressing non-phosphorylatable mutations exhibit altered behavioral rhythms. In particular, we observed that CK2-dependent phosphorylation of TIM(S1404) promotes nuclear accumulation of PER-TIM heterodimers by inhibiting the interaction of TIM and nuclear export component, Exportin 1 (XPO1). We propose that proper level of nuclear PER-TIM accumulation is necessary to facilitate kinase recruitment for the regulation of daily phosphorylation rhythm and phase-specific transcriptional activity of CLOCK (CLK). Our results highlight the contribution of phosphorylation-dependent nuclear export of PER-TIM heterodimers to the maintenance of circadian periodicity and identify a new mechanism by which the negative elements of the circadian clock (PER-TIM) regulate the positive elements (CLK-CYC). Finally, because the molecular phenotype of tim(S1404A) non-phosphorylatable mutant exhibits remarkable similarity to that of a mutation in human timeless that underlies familial advanced sleep phase syndrome (FASPS), our results revealed an unexpected parallel between the functions of Drosophila and human TIM and may provide new insights into the molecular mechanisms underlying human FASPS. Organisms in all domains of life exhibit circadian rhythms. Cai et al. reveal that phosphorylation of TIMELESS modulates kinase accessibility to CLOCK in the nucleus. This mechanism is important in controlling daily phosphorylation rhythm of CLOCK, which is critical for its function as a key regulator of circadian rhythms.
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Affiliation(s)
- Yao D Cai
- Department of Entomology and Nematology, College of Agricultural and Environmental Sciences, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Yongbo Xue
- Department of Biology, University of Nevada, Reno, NV 89557, USA
| | - Cindy C Truong
- Department of Entomology and Nematology, College of Agricultural and Environmental Sciences, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Jose Del Carmen-Li
- Department of Entomology and Nematology, College of Agricultural and Environmental Sciences, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Christopher Ochoa
- Department of Entomology and Nematology, College of Agricultural and Environmental Sciences, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Jens T Vanselow
- Rudolf Virchow Center for Experimental Biomedicine, University of Wurzburg, Wurzburg, Germany
| | - Katherine A Murphy
- Department of Entomology and Nematology, College of Agricultural and Environmental Sciences, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Ying H Li
- Department of Entomology and Nematology, College of Agricultural and Environmental Sciences, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Xianhui Liu
- Department of Entomology and Nematology, College of Agricultural and Environmental Sciences, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Ben L Kunimoto
- Department of Entomology and Nematology, College of Agricultural and Environmental Sciences, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA
| | - Haiyan Zheng
- Biological Mass Spectrometry Facility, Robert Wood Johnson Medical School and Rutgers, the State University of New Jersey, Piscataway, NJ 08854, USA
| | - Caifeng Zhao
- Biological Mass Spectrometry Facility, Robert Wood Johnson Medical School and Rutgers, the State University of New Jersey, Piscataway, NJ 08854, USA
| | - Yong Zhang
- Department of Biology, University of Nevada, Reno, NV 89557, USA
| | - Andreas Schlosser
- Rudolf Virchow Center for Experimental Biomedicine, University of Wurzburg, Wurzburg, Germany
| | - Joanna C Chiu
- Department of Entomology and Nematology, College of Agricultural and Environmental Sciences, University of California, Davis, One Shields Avenue, Davis, CA 95616, USA.
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21
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Yuan S, Peng L, Park JJ, Hu Y, Devarkar SC, Dong MB, Shen Q, Wu S, Chen S, Lomakin IB, Xiong Y. Nonstructural Protein 1 of SARS-CoV-2 Is a Potent Pathogenicity Factor Redirecting Host Protein Synthesis Machinery toward Viral RNA. Mol Cell 2020. [PMID: 33188728 DOI: 10.1101/2020.08.09.243451] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
The causative virus of the COVID-19 pandemic, SARS-CoV-2, uses its nonstructural protein 1 (Nsp1) to suppress cellular, but not viral, protein synthesis through yet unknown mechanisms. We show here that among all viral proteins, Nsp1 has the largest impact on host viability in the cells of human lung origin. Differential expression analysis of mRNA-seq data revealed that Nsp1 broadly alters the cellular transcriptome. Our cryo-EM structure of the Nsp1-40S ribosome complex shows that Nsp1 inhibits translation by plugging the mRNA entry channel of the 40S. We also determined the structure of the 48S preinitiation complex formed by Nsp1, 40S, and the cricket paralysis virus internal ribosome entry site (IRES) RNA, which shows that it is nonfunctional because of the incorrect position of the mRNA 3' region. Our results elucidate the mechanism of host translation inhibition by SARS-CoV-2 and advance understanding of the impacts from a major pathogenicity factor of SARS-CoV-2.
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MESH Headings
- Animals
- COVID-19/genetics
- COVID-19/metabolism
- COVID-19/pathology
- Chlorocebus aethiops
- Cryoelectron Microscopy
- Humans
- Protein Biosynthesis
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Viral/genetics
- RNA, Viral/metabolism
- Ribosome Subunits, Small, Eukaryotic/genetics
- Ribosome Subunits, Small, Eukaryotic/metabolism
- Ribosome Subunits, Small, Eukaryotic/ultrastructure
- Ribosome Subunits, Small, Eukaryotic/virology
- SARS-CoV-2/genetics
- SARS-CoV-2/metabolism
- SARS-CoV-2/pathogenicity
- SARS-CoV-2/ultrastructure
- Vero Cells
- Viral Nonstructural Proteins/genetics
- Viral Nonstructural Proteins/metabolism
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Affiliation(s)
- Shuai Yuan
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, USA
| | - Lei Peng
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06520, USA; Systems Biology Institute, Yale University, West Haven, CT 06516, USA
| | - Jonathan J Park
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06520, USA; Systems Biology Institute, Yale University, West Haven, CT 06516, USA
| | - Yingxia Hu
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, USA
| | - Swapnil C Devarkar
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, USA
| | - Matthew B Dong
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06520, USA; Systems Biology Institute, Yale University, West Haven, CT 06516, USA
| | - Qi Shen
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, USA
| | - Shenping Wu
- Department of Pharmacology, Yale University, West Haven, CT 06516, USA
| | - Sidi Chen
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06520, USA; Systems Biology Institute, Yale University, West Haven, CT 06516, USA.
| | - Ivan B Lomakin
- Department of Dermatology, Yale University School of Medicine, New Haven, CT 06520, USA.
| | - Yong Xiong
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, USA.
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22
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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.
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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.
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23
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Kratzat H, Mackens-Kiani T, Ameismeier M, Potocnjak M, Cheng J, Dacheux E, Namane A, Berninghausen O, Herzog F, Fromont-Racine M, Becker T, Beckmann R. A structural inventory of native ribosomal ABCE1-43S pre-initiation complexes. EMBO J 2020; 40:e105179. [PMID: 33289941 PMCID: PMC7780240 DOI: 10.15252/embj.2020105179] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Revised: 09/21/2020] [Accepted: 09/29/2020] [Indexed: 11/24/2022] Open
Abstract
In eukaryotic translation, termination and ribosome recycling phases are linked to subsequent initiation of a new round of translation by persistence of several factors at ribosomal sub‐complexes. These comprise/include the large eIF3 complex, eIF3j (Hcr1 in yeast) and the ATP‐binding cassette protein ABCE1 (Rli1 in yeast). The ATPase is mainly active as a recycling factor, but it can remain bound to the dissociated 40S subunit until formation of the next 43S pre‐initiation complexes. However, its functional role and native architectural context remains largely enigmatic. Here, we present an architectural inventory of native yeast and human ABCE1‐containing pre‐initiation complexes by cryo‐EM. We found that ABCE1 was mostly associated with early 43S, but also with later 48S phases of initiation. It adopted a novel hybrid conformation of its nucleotide‐binding domains, while interacting with the N‐terminus of eIF3j. Further, eIF3j occupied the mRNA entry channel via its ultimate C‐terminus providing a structural explanation for its antagonistic role with respect to mRNA binding. Overall, the native human samples provide a near‐complete molecular picture of the architecture and sophisticated interaction network of the 43S‐bound eIF3 complex and the eIF2 ternary complex containing the initiator tRNA.
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Affiliation(s)
- Hanna Kratzat
- Gene Center and Center for Integrated Protein Science Munich, Department of Biochemistry, University of Munich, Munich, Germany
| | - Timur Mackens-Kiani
- Gene Center and Center for Integrated Protein Science Munich, Department of Biochemistry, University of Munich, Munich, Germany
| | - Michael Ameismeier
- Gene Center and Center for Integrated Protein Science Munich, Department of Biochemistry, University of Munich, Munich, Germany
| | - Mia Potocnjak
- Gene Center and Center for Integrated Protein Science Munich, Department of Biochemistry, University of Munich, Munich, Germany
| | - Jingdong Cheng
- Gene Center and Center for Integrated Protein Science Munich, Department of Biochemistry, University of Munich, Munich, Germany
| | - Estelle Dacheux
- Génétique des Interactions Macromoléculaires, UMR3525 CNRS, Institut Pasteur, Paris, France
| | - Abdelkader Namane
- Génétique des Interactions Macromoléculaires, UMR3525 CNRS, Institut Pasteur, Paris, France
| | - Otto Berninghausen
- Gene Center and Center for Integrated Protein Science Munich, Department of Biochemistry, University of Munich, Munich, Germany
| | - Franz Herzog
- Gene Center and Center for Integrated Protein Science Munich, Department of Biochemistry, University of Munich, Munich, Germany
| | | | - Thomas Becker
- Gene Center and Center for Integrated Protein Science Munich, Department of Biochemistry, University of Munich, Munich, Germany
| | - Roland Beckmann
- Gene Center and Center for Integrated Protein Science Munich, Department of Biochemistry, University of Munich, Munich, Germany
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24
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Brito Querido J, Sokabe M, Kraatz S, Gordiyenko Y, Skehel JM, Fraser CS, Ramakrishnan V. Structure of a human 48 S translational initiation complex. Science 2020; 369:1220-1227. [PMID: 32883864 DOI: 10.1126/science.aba4904] [Citation(s) in RCA: 107] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Accepted: 07/07/2020] [Indexed: 12/20/2022]
Abstract
A key step in translational initiation is the recruitment of the 43S preinitiation complex by the cap-binding complex [eukaryotic initiation factor 4F (eIF4F)] at the 5' end of messenger RNA (mRNA) to form the 48S initiation complex (i.e., the 48S). The 48S then scans along the mRNA to locate a start codon. To understand the mechanisms involved, we used cryo-electron microscopy to determine the structure of a reconstituted human 48S The structure reveals insights into early events of translation initiation complex assembly, as well as how eIF4F interacts with subunits of eIF3 near the mRNA exit channel in the 43S The location of eIF4F is consistent with a slotting model of mRNA recruitment and suggests that downstream mRNA is unwound at least in part by being "pulled" through the 40S subunit during scanning.
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Affiliation(s)
| | - Masaaki Sokabe
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, CA, USA
| | | | | | | | - Christopher S Fraser
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, CA, USA.
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25
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Yuan S, Peng L, Park JJ, Hu Y, Devarkar SC, Dong MB, Shen Q, Wu S, Chen S, Lomakin IB, Xiong Y. Nonstructural Protein 1 of SARS-CoV-2 Is a Potent Pathogenicity Factor Redirecting Host Protein Synthesis Machinery toward Viral RNA. Mol Cell 2020; 80:1055-1066.e6. [PMID: 33188728 PMCID: PMC7833686 DOI: 10.1016/j.molcel.2020.10.034] [Citation(s) in RCA: 124] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 10/05/2020] [Accepted: 10/22/2020] [Indexed: 12/22/2022]
Abstract
The causative virus of the COVID-19 pandemic, SARS-CoV-2, uses its nonstructural protein 1 (Nsp1) to suppress cellular, but not viral, protein synthesis through yet unknown mechanisms. We show here that among all viral proteins, Nsp1 has the largest impact on host viability in the cells of human lung origin. Differential expression analysis of mRNA-seq data revealed that Nsp1 broadly alters the cellular transcriptome. Our cryo-EM structure of the Nsp1-40S ribosome complex shows that Nsp1 inhibits translation by plugging the mRNA entry channel of the 40S. We also determined the structure of the 48S preinitiation complex formed by Nsp1, 40S, and the cricket paralysis virus internal ribosome entry site (IRES) RNA, which shows that it is nonfunctional because of the incorrect position of the mRNA 3′ region. Our results elucidate the mechanism of host translation inhibition by SARS-CoV-2 and advance understanding of the impacts from a major pathogenicity factor of SARS-CoV-2.
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MESH Headings
- Animals
- COVID-19/genetics
- COVID-19/metabolism
- COVID-19/pathology
- Chlorocebus aethiops
- Cryoelectron Microscopy
- Humans
- Protein Biosynthesis
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- RNA, Viral/genetics
- RNA, Viral/metabolism
- Ribosome Subunits, Small, Eukaryotic/genetics
- Ribosome Subunits, Small, Eukaryotic/metabolism
- Ribosome Subunits, Small, Eukaryotic/ultrastructure
- Ribosome Subunits, Small, Eukaryotic/virology
- SARS-CoV-2/genetics
- SARS-CoV-2/metabolism
- SARS-CoV-2/pathogenicity
- SARS-CoV-2/ultrastructure
- Vero Cells
- Viral Nonstructural Proteins/genetics
- Viral Nonstructural Proteins/metabolism
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Affiliation(s)
- Shuai Yuan
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, USA
| | - Lei Peng
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06520, USA; Systems Biology Institute, Yale University, West Haven, CT 06516, USA
| | - Jonathan J Park
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06520, USA; Systems Biology Institute, Yale University, West Haven, CT 06516, USA
| | - Yingxia Hu
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, USA
| | - Swapnil C Devarkar
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, USA
| | - Matthew B Dong
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06520, USA; Systems Biology Institute, Yale University, West Haven, CT 06516, USA
| | - Qi Shen
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, USA
| | - Shenping Wu
- Department of Pharmacology, Yale University, West Haven, CT 06516, USA
| | - Sidi Chen
- Department of Genetics, Yale University School of Medicine, New Haven, CT 06520, USA; Systems Biology Institute, Yale University, West Haven, CT 06516, USA.
| | - Ivan B Lomakin
- Department of Dermatology, Yale University School of Medicine, New Haven, CT 06520, USA.
| | - Yong Xiong
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, CT 06511, USA.
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26
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Young DJ, Guydosh NR. Hcr1/eIF3j Is a 60S Ribosomal Subunit Recycling Accessory Factor In Vivo. Cell Rep 2020; 28:39-50.e4. [PMID: 31269449 DOI: 10.1016/j.celrep.2019.05.111] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2018] [Revised: 04/26/2019] [Accepted: 05/30/2019] [Indexed: 02/07/2023] Open
Abstract
Hcr1/eIF3j is a sub-stoichiometric subunit of eukaryotic initiation factor 3 (eIF3) that can dissociate the post-termination 40S ribosomal subunit from mRNA in vitro. We examine this ribosome recycling role in vivo by ribosome profiling and reporter assays and find that loss of Hcr1 leads to reinitiation of translation in 3' UTRs, consistent with a defect in recycling. However, the defect appears to be in the recycling of the 60S subunit, rather than the 40S subunit, because reinitiation does not require an AUG codon and is suppressed by overexpression of the 60S dissociation factor Rli1/ABCE1. Consistent with a 60S recycling role, overexpression of Hcr1 cannot compensate for loss of 40S recycling factors Tma64/eIF2D and Tma20/MCT-1. Intriguingly, loss of Hcr1 triggers greater expression of RLI1 via an apparent feedback loop. These findings suggest Hcr1/eIF3j is recruited to ribosomes at stop codons and may coordinate the transition to a new round of translation.
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Affiliation(s)
- David J Young
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA
| | - Nicholas R Guydosh
- Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, NIH, Bethesda, MD 20892, USA.
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27
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Sharma J, Keeling KM, Rowe SM. Pharmacological approaches for targeting cystic fibrosis nonsense mutations. Eur J Med Chem 2020; 200:112436. [PMID: 32512483 DOI: 10.1016/j.ejmech.2020.112436] [Citation(s) in RCA: 21] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2020] [Revised: 05/04/2020] [Accepted: 05/06/2020] [Indexed: 12/11/2022]
Abstract
Cystic fibrosis (CF) is a monogenic autosomal recessive disorder. The clinical manifestations of the disease are caused by ∼2,000 mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) protein. It is unlikely that any one approach will be efficient in correcting all defects. The recent approvals of ivacaftor, lumacaftor/ivacaftor and elexacaftor/tezacaftor/ivacaftor represent the genesis of a new era of precision combination medicine for the CF patient population. In this review, we discuss targeted translational readthrough approaches as mono and combination therapies for CFTR nonsense mutations. We examine the current status of efficacy of translational readthrough/nonsense suppression therapies and their limitations, including non-native amino acid incorporation at PTCs and nonsense-mediated mRNA decay (NMD), along with approaches to tackle these limitations. We further elaborate on combining various therapies such as readthrough agents, NMD inhibitors, and corrector/potentiators to improve the efficacy and safety of suppression therapy. These mutation specific strategies that are directed towards the basic CF defects should positively impact CF patients bearing nonsense mutations.
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Affiliation(s)
- Jyoti Sharma
- Department of Medicine, University of Alabama at Birmingham (UAB), USA; Department of Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), USA
| | - Kim M Keeling
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham (UAB), USA; Department of Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), USA
| | - Steven M Rowe
- Department of Medicine, University of Alabama at Birmingham (UAB), USA; Department of Pediatrics, University of Alabama at Birmingham (UAB), USA; Department of Gregory Fleming James Cystic Fibrosis Research Center, University of Alabama at Birmingham (UAB), USA.
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28
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Ribosomal Protein L13 Promotes IRES-Driven Translation of Foot-and-Mouth Disease Virus in a Helicase DDX3-Dependent Manner. J Virol 2020; 94:JVI.01679-19. [PMID: 31619563 DOI: 10.1128/jvi.01679-19] [Citation(s) in RCA: 34] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2019] [Accepted: 10/11/2019] [Indexed: 12/22/2022] Open
Abstract
Internal ribosome entry site (IRES)-driven translation is a common strategy among positive-sense, single-stranded RNA viruses for bypassing the host cell requirement of a 5' cap structure. In the current study, we identified the ribosomal protein L13 (RPL13) as a critical regulator of IRES-driven translation of foot-and-mouth disease virus (FMDV) but found that it is not essential for cellular global translation. RPL13 is also a determinant for translation and infection of Seneca Valley virus (SVV) and classical swine fever virus (CSFV), and this suggests that its function may also be conserved in unrelated IRES-containing viruses. We further showed that depletion of DEAD box helicase DDX3 disrupts binding of RPL13 to the FMDV IRES, whereas the reduction in RPL13 expression impairs the ability of DDX3 to promote IRES-driven translation directly. DDX3 cooperates with RPL13 to support the assembly of 80S ribosomes for optimal translation initiation of viral mRNA. Finally, we demonstrated that DDX3 affects the recruitment of the eukaryotic initiation factor eIF3 subunits e and j to the viral IRES. This work provides the first connection between DDX3 and eIF3e/j and recognition of the role of RPL13 in modulating viral IRES-dependent translation. This previously uncharacterized process may be involved in selective mRNA translation.IMPORTANCE Accumulating evidence has unveiled the roles of ribosomal proteins (RPs) belonging to the large 60S subunit in regulating selective translation of specific mRNAs. The translation specificity of the large-subunit RPs in this process is thought provoking, given the role they play canonically in catalyzing peptide bond formation. Here, we have identified the ribosomal protein L13 (RPL13) as a critical regulator of IRES-driven translation during FMDV infection. Our study supports a model whereby the FMDV IRESs recruit helicase DDX3 recognizing RPL13 to facilitate IRES-driven translation, with the assistance of eIF3e and eIF3j. A better understanding of these specific interactions surrounding IRES-mediated translation initiation could have important implications for the selective translation of viral mRNA and thus for the development of effective prevention of viral infection.
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29
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Tetrapeptide 60-63 of human ribosomal protein uS3 is crucial for translation initiation. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2019; 1862:194411. [PMID: 31356988 DOI: 10.1016/j.bbagrm.2019.194411] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 07/16/2019] [Accepted: 07/16/2019] [Indexed: 12/14/2022]
Abstract
Conserved ribosomal protein uS3 contains a decapeptide fragment in positions 55-64 (human numbering), which has a very specific ability to cross-link to various RNA derivatives bearing aldehyde groups, likely provided by K62. It has been shown that during translation in the cell-free protein-synthesizing system, uS3 becomes accessible for such cross-linking only after eIF3j leaves the mRNA binding channel of the 40S ribosomal subunit. We studied the functional role of K62 and its nearest neighbors in the ribosomal assembly and translation with the use of HEK293T-derived cell cultures capable of producing FLAG-tagged uS3 (uS3FLAG) or its mutant form with amino acid residues at positions 60-63 replaced with alanines. Analysis of polysome profiles from the respective cells and cytosol lysates showed that the mutation significantly affected the uS3 ability to participate in the assembly of 40S subunits, but it was not essential for their maturation and did not prevent the binding of mRNAs to 40S subunits during translation initiation. The most striking effect of the replacement of amino acid residues in the above uS3 positions was that it almost completely deprived the 40S subunits of their ability to form 80S ribosomes, suggesting that the 48S pre-initiation complexes assembled on these subunits were defective in the binding of 60S subunits. Thus, our results revealed the previously unknown crucial role of the uS3 tetrapeptide 60GEKG63 in translation initiation related to maintaining the proper structure of the 48S complex, most likely via the prevention of premature mRNA loading into the ribosomal channel.
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30
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Johnson AG, Petrov AN, Fuchs G, Majzoub K, Grosely R, Choi J, Puglisi JD. Fluorescently-tagged human eIF3 for single-molecule spectroscopy. Nucleic Acids Res 2019; 46:e8. [PMID: 29136179 PMCID: PMC5778468 DOI: 10.1093/nar/gkx1050] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 10/24/2017] [Indexed: 01/09/2023] Open
Abstract
Human translation initiation relies on the combined activities of numerous ribosome-associated eukaryotic initiation factors (eIFs). The largest factor, eIF3, is an ∼800 kDa multiprotein complex that orchestrates a network of interactions with the small 40S ribosomal subunit, other eIFs, and mRNA, while participating in nearly every step of initiation. How these interactions take place during the time course of translation initiation remains unclear. Here, we describe a method for the expression and affinity purification of a fluorescently-tagged eIF3 from human cells. The tagged eIF3 dodecamer is structurally intact, functions in cell-based assays, and interacts with the HCV IRES mRNA and the 40S-IRES complex in vitro. By tracking the binding of single eIF3 molecules to the HCV IRES RNA with a zero-mode waveguides-based instrument, we show that eIF3 samples both wild-type IRES and an IRES that lacks the eIF3-binding region, and that the high-affinity eIF3-IRES interaction is largely determined by slow dissociation kinetics. The application of single-molecule methods to more complex systems involving eIF3 may unveil dynamics underlying mRNA selection and ribosome loading during human translation initiation.
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Affiliation(s)
- Alex G Johnson
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA 94305, USA.,Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
| | - Alexey N Petrov
- Department of Biological Sciences, Auburn University, Auburn, AL 36849, USA
| | - Gabriele Fuchs
- The RNA Institute, Department of Biological Sciences, University of Albany, Albany, NY 12222, USA
| | - Karim Majzoub
- Department of Microbiology and Immunology, Stanford University, Stanford, CA 94305, USA
| | - Rosslyn Grosely
- Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
| | - Junhong Choi
- Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
| | - Joseph D Puglisi
- Department of Structural Biology, Stanford University, Stanford, CA 94305, USA
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31
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Genuth NR, Barna M. Heterogeneity and specialized functions of translation machinery: from genes to organisms. Nat Rev Genet 2019; 19:431-452. [PMID: 29725087 DOI: 10.1038/s41576-018-0008-z] [Citation(s) in RCA: 141] [Impact Index Per Article: 28.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Regulation of mRNA translation offers the opportunity to diversify the expression and abundance of proteins made from individual gene products in cells, tissues and organisms. Emerging evidence has highlighted variation in the composition and activity of several large, highly conserved translation complexes as a means to differentially control gene expression. Heterogeneity and specialized functions of individual components of the ribosome and of the translation initiation factor complexes eIF3 and eIF4F, which are required for recruitment of the ribosome to the mRNA 5' untranslated region, have been identified. In this Review, we summarize the evidence for selective mRNA translation by components of these macromolecular complexes as a means to dynamically control the translation of the proteome in time and space. We further discuss the implications of this form of gene expression regulation for a growing number of human genetic disorders associated with mutations in the translation machinery.
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Affiliation(s)
- Naomi R Genuth
- Departments of Genetics and Developmental Biology, Stanford University, Stanford, CA, USA.,Department of Biology, Stanford University, Stanford, CA, USA
| | - Maria Barna
- Departments of Genetics and Developmental Biology, Stanford University, Stanford, CA, USA.
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32
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Johnson AG, Lapointe CP, Wang J, Corsepius NC, Choi J, Fuchs G, Puglisi JD. RACK1 on and off the ribosome. RNA (NEW YORK, N.Y.) 2019; 25:881-895. [PMID: 31023766 PMCID: PMC6573788 DOI: 10.1261/rna.071217.119] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/12/2019] [Accepted: 04/21/2019] [Indexed: 05/17/2023]
Abstract
Receptor for activated C kinase 1 (RACK1) is a eukaryote-specific ribosomal protein (RP) implicated in diverse biological functions. To engineer ribosomes for specific fluorescent labeling, we selected RACK1 as a target given its location on the small ribosomal subunit and other properties. However, prior results suggested that RACK1 has roles both on and off the ribosome, and such an exchange might be related to its various cellular functions and hinder our ability to use RACK1 as a stable fluorescent tag for the ribosome. In addition, the kinetics of spontaneous exchange of RACK1 or any RP from a mature ribosome in vitro remain unclear. To address these issues, we engineered fluorescently labeled human ribosomes via RACK1, and applied bulk and single-molecule biochemical analyses to track RACK1 on and off the human ribosome. Our results demonstrate that, despite its cellular nonessentiality from yeast to humans, RACK1 readily reassociates with the ribosome, displays limited conformational dynamics, and remains stably bound to the ribosome for hours in vitro. This work sheds insight into the biochemical basis of RPs exchange on and off a mature ribosome and provides tools for single-molecule analysis of human translation.
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Affiliation(s)
- Alex G Johnson
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305, USA
- Department of Chemical and Systems Biology, Stanford University School of Medicine, Stanford, California 94305, USA
| | - Christopher P Lapointe
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305, USA
| | - Jinfan Wang
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305, USA
| | - Nicholas C Corsepius
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305, USA
| | - Junhong Choi
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305, USA
- Department of Applied Physics, Stanford University, Stanford, California 94305, USA
| | - Gabriele Fuchs
- The RNA Institute, Department of Biological Sciences, University of Albany, Albany, New York 12222, USA
| | - Joseph D Puglisi
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305, USA
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Abstract
The eukaryotic translation pathway has been studied for more than four decades, but the molecular mechanisms that regulate each stage of the pathway are not completely defined. This is in part because we have very little understanding of the kinetic framework for the assembly and disassembly of pathway intermediates. Steps of the pathway are thought to occur in the subsecond to second time frame, but most assays to monitor these events require minutes to hours to complete. Understanding translational control in sufficient detail will therefore require the development of assays that can precisely monitor the kinetics of the translation pathway in real time. Here, we describe the translation pathway from the perspective of its kinetic parameters, discuss advances that are helping us move toward the goal of a rigorous kinetic understanding, and highlight some of the challenges that remain.
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Abstract
In the past 4 years, because of the advent of new cameras, many ribosome structures have been solved by cryoelectron microscopy (cryo-EM) at high, often near-atomic resolution, bringing new mechanistic insights into the processes of translation initiation, peptide elongation, termination, and recycling. Thus, cryo-EM has joined X-ray crystallography as a powerful technique in structural studies of translation. The significance of this new development is that structures of ribosomes in complex with their functional binding partners can now be determined to high resolution in multiple states as they perform their work. The aim of this article is to provide an overview of these new studies and assess the contributions they have made toward an understanding of translation and translational control.
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Merrick WC, Pavitt GD. Protein Synthesis Initiation in Eukaryotic Cells. Cold Spring Harb Perspect Biol 2018; 10:cshperspect.a033092. [PMID: 29735639 DOI: 10.1101/cshperspect.a033092] [Citation(s) in RCA: 197] [Impact Index Per Article: 32.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
This review summarizes our current understanding of the major pathway for the initiation phase of protein synthesis in eukaryotic cells, with a focus on recent advances. We describe the major scanning or messenger RNA (mRNA) m7G cap-dependent mechanism, which is a highly coordinated and stepwise regulated process that requires the combined action of at least 12 distinct translation factors with initiator transfer RNA (tRNA), ribosomes, and mRNAs. We limit our review to studies involving either mammalian or budding yeast cells and factors, as these represent the two best-studied experimental systems, and only include a reference to other organisms where particular insight has been gained. We close with a brief description of what we feel are some of the major unknowns in eukaryotic initiation.
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Affiliation(s)
- William C Merrick
- Department of Biochemistry, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106
| | - Graham D Pavitt
- Division of Molecular and Cellular Function, Faculty of Biology Medicine and Health, Manchester Academic Health Science Centre, The University of Manchester, Manchester M13 9PT, United Kingdom
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Abstract
In mammals, cap-dependent translation of mRNAs is initiated by two distinct mechanisms: cap-binding complex (CBC; a heterodimer of CBP80 and 20)-dependent translation (CT) and eIF4E-dependent translation (ET). Both translation initiation mechanisms share common features in driving cap-dependent translation; nevertheless, they can be distinguished from each other based on their molecular features and biological roles. CT is largely associated with mRNA surveillance such as nonsense-mediated mRNA decay (NMD), whereas ET is predominantly involved in the bulk of protein synthesis. However, several recent studies have demonstrated that CT and ET have similar roles in protein synthesis and mRNA surveillance. In a subset of mRNAs, CT preferentially drives the cap-dependent translation, as ET does, and ET is responsible for mRNA surveillance, as CT does. In this review, we summarize and compare the molecular features of CT and ET with a focus on the emerging roles of CT in translation.
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Affiliation(s)
- Incheol Ryu
- Creative Research Initiatives Center for Molecular Biology of Translation, Korea University, Seoul 02841,
Korea
- School of Life Sciences, Korea University, Seoul 02841,
Korea
| | - Yoon Ki Kim
- Creative Research Initiatives Center for Molecular Biology of Translation, Korea University, Seoul 02841,
Korea
- School of Life Sciences, Korea University, Seoul 02841,
Korea
- Corresponding author. Tel: +82-2-3290-3410; Fax: +82-2-923-9923; E-mail:
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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.
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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
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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’.
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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
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A helicase-independent activity of eIF4A in promoting mRNA recruitment to the human ribosome. Proc Natl Acad Sci U S A 2017; 114:6304-6309. [PMID: 28559306 DOI: 10.1073/pnas.1620426114] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
In the scanning model of translation initiation, the decoding site and latch of the 40S subunit must open to allow the recruitment and migration of messenger RNA (mRNA); however, the precise molecular details for how initiation factors regulate mRNA accommodation into the decoding site have not yet been elucidated. Eukaryotic initiation factor (eIF) 3j is a subunit of eIF3 that binds to the mRNA entry channel and A-site of the 40S subunit. Previous studies have shown that a reduced affinity of eIF3j for the 43S preinitiation complex (PIC) occurs on eIF4F-dependent mRNA recruitment. Because eIF3j and mRNA bind anticooperatively to the 43S PIC, reduced eIF3j affinity likely reflects a state of full accommodation of mRNA into the decoding site. Here, we have used a fluorescence-based anisotropy assay to quantitatively determine how initiation components coordinate their activities to reduce the affinity of eIF3j during the recruitment of mRNA to the 43S PIC. Unexpectedly, we show that a full reduction in eIF3j affinity for the 43S PIC requires an ATP-dependent, but unwinding-independent, activity of eIF4A. This result suggests that in addition to its helicase activity, eIF4A uses the free energy of ATP binding and hydrolysis as a regulatory switch to control the conformation of the 43S PIC during mRNA recruitment. Therefore, our results define eIF4A as a universal initiation factor in cap-dependent translation initiation that functions beyond its role in RNA unwinding.
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40
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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: 199] [Impact Index Per Article: 28.4] [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.
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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.
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41
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Role of Eukaryotic Initiation Factors during Cellular Stress and Cancer Progression. J Nucleic Acids 2016; 2016:8235121. [PMID: 28083147 PMCID: PMC5204094 DOI: 10.1155/2016/8235121] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2016] [Accepted: 11/14/2016] [Indexed: 12/12/2022] Open
Abstract
Protein synthesis can be segmented into distinct phases comprising mRNA translation initiation, elongation, and termination. Translation initiation is a highly regulated and rate-limiting step of protein synthesis that requires more than 12 eukaryotic initiation factors (eIFs). Extensive evidence shows that the transcriptome and corresponding proteome do not invariably correlate with each other in a variety of contexts. In particular, translation of mRNAs specific to angiogenesis, tumor development, and apoptosis is altered during physiological and pathophysiological stress conditions. In cancer cells, the expression and functions of eIFs are hampered, resulting in the inhibition of global translation and enhancement of translation of subsets of mRNAs by alternative mechanisms. A precise understanding of mechanisms involving eukaryotic initiation factors leading to differential protein expression can help us to design better strategies to diagnose and treat cancer. The high spatial and temporal resolution of translation control can have an immediate effect on the microenvironment of the cell in comparison with changes in transcription. The dysregulation of mRNA translation mechanisms is increasingly being exploited as a target to treat cancer. In this review, we will focus on this context by describing both canonical and noncanonical roles of eIFs, which alter mRNA translation.
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42
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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
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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
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Barbosa NM, Boldrin PEG, Rossi D, Yamamoto PA, Watanabe TF, Serrão VH, Hershey JWB, Fraser CS, Valentini SR, Zanelli CF. Mapping surface residues of eIF5A that are important for binding to the ribosome using alanine scanning mutagenesis. Amino Acids 2016; 48:2363-74. [PMID: 27388480 PMCID: PMC5897047 DOI: 10.1007/s00726-016-2279-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2016] [Accepted: 06/11/2016] [Indexed: 01/15/2023]
Abstract
The translation elongation factor eIF5A is conserved through evolution and is necessary to rescue the ribosome during translation elongation of polyproline-containing proteins. Although the site of eIF5A binding to the ribosome is known, no systematic analysis has been performed so far to determine the important residues on the surface of eIF5A required for ribosome binding. In this study, we used clustered charged-to-alanine mutagenesis and structural modeling to address this question. We generated four new mutants of yeast eIF5A: tif51A-4, tif51A-6, tif51A-7 and tif51A-11, and complementation analysis revealed that tif51A-4 and tif51A-7 could not sustain cell growth in a strain lacking wild-type eIF5A. Moreover, the allele tif51A-4 also displayed negative dominance over wild-type eIF5A. Both in vivo GST-pulldowns and in vitro fluorescence anisotropy demonstrated that eIF5A from mutant tif51A-7 exhibited an importantly reduced affinity for the ribosome, implicating the charged residues in cluster 7 as determinant features on the eIF5A surface for contacting the ribosome. Notably, modified eIF5A from mutant tif51A-4, despite exhibiting the most severe growth phenotype, did not abolish ribosome interactions as with mutant tif51A-7. Taking into account the modeling eIF5A + 80S + P-tRNA complex, our data suggest that interactions of eIF5A with ribosomal protein L1 are more important to stabilize the interaction with the ribosome as a whole than the contacts with P-tRNA. Finally, the ability of eIF5A from tif51A-4 to bind to the ribosome while potentially blocking physical interaction with P-tRNA could explain its dominant negative phenotype.
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Affiliation(s)
- Natália M Barbosa
- Department of Biological Sciences, School of Pharmaceutical Sciences, São Paulo State University-UNESP, Rod Araraquara-Jaú Km01, Araraquara, SP, 14800-903, Brazil
| | - Paulo E G Boldrin
- Department of Biological Sciences, School of Pharmaceutical Sciences, São Paulo State University-UNESP, Rod Araraquara-Jaú Km01, Araraquara, SP, 14800-903, Brazil
| | - Danuza Rossi
- Department of Biological Sciences, School of Pharmaceutical Sciences, São Paulo State University-UNESP, Rod Araraquara-Jaú Km01, Araraquara, SP, 14800-903, Brazil
| | - Priscila A Yamamoto
- Department of Biological Sciences, School of Pharmaceutical Sciences, São Paulo State University-UNESP, Rod Araraquara-Jaú Km01, Araraquara, SP, 14800-903, Brazil
| | - Tatiana F Watanabe
- Department of Biological Sciences, School of Pharmaceutical Sciences, São Paulo State University-UNESP, Rod Araraquara-Jaú Km01, Araraquara, SP, 14800-903, Brazil
| | - Vitor H Serrão
- Physics and Interdisciplinary Science Department, Physics Institute of Sao Carlos, University of Sao Paulo-USP, Sao Carlos, SP, 13563-120, Brazil
| | - John W B Hershey
- Molecular and Cellular Biology Department, University of California, Davis, CA, 95616, USA
| | - Christopher S Fraser
- Molecular and Cellular Biology Department, University of California, Davis, CA, 95616, USA
| | - Sandro R Valentini
- Department of Biological Sciences, School of Pharmaceutical Sciences, São Paulo State University-UNESP, Rod Araraquara-Jaú Km01, Araraquara, SP, 14800-903, Brazil
| | - Cleslei F Zanelli
- Department of Biological Sciences, School of Pharmaceutical Sciences, São Paulo State University-UNESP, Rod Araraquara-Jaú Km01, Araraquara, SP, 14800-903, Brazil.
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Sharifulin DE, Bartuli YS, Meschaninova MI, Ven'yaminova AG, Graifer DM, Karpova GG. Exploring accessibility of structural elements of the mammalian 40S ribosomal mRNA entry channel at various steps of translation initiation. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2016; 1864:1328-38. [DOI: 10.1016/j.bbapap.2016.06.011] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2016] [Revised: 06/20/2016] [Accepted: 06/22/2016] [Indexed: 02/05/2023]
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Rossi D, Barbosa NM, Galvão FC, Boldrin PEG, Hershey JWB, Zanelli CF, Fraser CS, Valentini SR. Evidence for a Negative Cooperativity between eIF5A and eEF2 on Binding to the Ribosome. PLoS One 2016; 11:e0154205. [PMID: 27115996 PMCID: PMC4845985 DOI: 10.1371/journal.pone.0154205] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Accepted: 04/10/2016] [Indexed: 01/04/2023] Open
Abstract
eIF5A is the only protein known to contain the essential and unique amino acid residue hypusine. eIF5A functions in both translation initiation due to its stimulation of methionyl-puromycin synthesis and translation elongation, being highly required for peptide-bound formation of specific ribosome stalling sequences such as poly-proline. The functional interaction between eIF5A, tRNA, and eEF2 on the surface of the ribosome is further clarified herein. Fluorescence anisotropy assays were performed to determine the affinity of eIF5A to different ribosomal complexes and reveal its interaction exclusively and directly with the 60S ribosomal subunit in a hypusine-dependent manner (Ki60S-eIF5A-Hyp = 16 nM, Ki60S-eIF5A-Lys = 385 nM). A 3-fold increase in eIF5A affinity to the 80S is observed upon charged-tRNAiMet binding, indicating positive cooperativity between P-site tRNA binding and eIF5A binding to the ribosome. Previously identified conditional mutants of yeast eIF5A, eIF5AQ22H/L93F and eIF5AK56A, display a significant decrease in ribosome binding affinity. Binding affinity between ribosome and eIF5A-wild type or mutants eIF5AK56A, but not eIF5AQ22H/L93F, is impaired in the presence of eEF2 by 4-fold, consistent with negative cooperativity between eEF2 and eIF5A binding to the ribosome. Interestingly, high-copy eEF2 is toxic only to eIF5AQ22H/L93F and causes translation elongation defects in this mutant. These results suggest that binding of eEF2 to the ribosome alters its conformation, resulting in a weakened affinity of eIF5A and impairment of this interplay compromises cell growth due to translation elongation defects.
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Affiliation(s)
- Danuza Rossi
- School of Pharmaceutical Sciences, UNESP - Univ Estadual Paulista, Department of Biological Sciences, Araraquara, SP, Brazil, 14801
- Department of Molecular and Cellular Biology, University of California Davis, Davis, CA, United States of America, 95616
| | - Natalia M. Barbosa
- School of Pharmaceutical Sciences, UNESP - Univ Estadual Paulista, Department of Biological Sciences, Araraquara, SP, Brazil, 14801
| | - Fabio C. Galvão
- School of Pharmaceutical Sciences, UNESP - Univ Estadual Paulista, Department of Biological Sciences, Araraquara, SP, Brazil, 14801
| | - Paulo E. G. Boldrin
- School of Pharmaceutical Sciences, UNESP - Univ Estadual Paulista, Department of Biological Sciences, Araraquara, SP, Brazil, 14801
| | - John W. B. Hershey
- Department of Molecular and Cellular Biology, University of California Davis, Davis, CA, United States of America, 95616
| | - Cleslei F. Zanelli
- School of Pharmaceutical Sciences, UNESP - Univ Estadual Paulista, Department of Biological Sciences, Araraquara, SP, Brazil, 14801
| | - Christopher S. Fraser
- Department of Molecular and Cellular Biology, University of California Davis, Davis, CA, United States of America, 95616
| | - Sandro R. Valentini
- School of Pharmaceutical Sciences, UNESP - Univ Estadual Paulista, Department of Biological Sciences, Araraquara, SP, Brazil, 14801
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Chicher J, Simonetti A, Kuhn L, Schaeffer L, Hammann P, Eriani G, Martin F. Purification of mRNA-programmed translation initiation complexes suitable for mass spectrometry analysis. Proteomics 2015; 15:2417-25. [PMID: 25914180 DOI: 10.1002/pmic.201400628] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2014] [Revised: 02/27/2015] [Accepted: 04/21/2015] [Indexed: 12/21/2022]
Abstract
Liquid Chromatography coupled to tandem mass spectrometry (nanoLC-MS/MS) is a powerful analytical technique for the identification and mass analysis of complex protein mixtures. Here, we present a combination of methods developed for the extensive/deep proteomic analysis of purified ribosome/mRNA particles assembled in rabbit reticulocyte lysate (RRL). Ribosomes are assembled on chimeric biotinylated mRNA-DNA molecules immobilized on streptavidin-coated beads and incubated with RRL to form initiation complexes. After washing steps, the complexes are trypsin-digested directly on the beads in semi-native condition or after their elution from the beads in denaturing Laemmli buffer. The nanoLC-MS/MS analysis performed on complexes assembled on β-globin, viral HCV, and histone H4 mRNAs revealed significant differences in initiation factors composition in agreement with models of translation initiation used by these different types of mRNAs. Using Laemmli-denaturing condition induces release of deeply buried peptides from the ribosome and eukaryotic initiation factor 3 (eIF3) allowing the identification of the nearly complete set of ribosomal proteins.
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Affiliation(s)
- Johana Chicher
- Institut de Biologie Moléculaire et Cellulaire, Plateforme Protéomique Strasbourg - Esplanade, Université De Strasbourg, Strasbourg, France
| | - Angelita Simonetti
- Institut de Biologie Moléculaire et Cellulaire, "Architecture et Réactivité de l'ARN", Université De Strasbourg, Strasbourg, France
| | - Lauriane Kuhn
- Institut de Biologie Moléculaire et Cellulaire, Plateforme Protéomique Strasbourg - Esplanade, Université De Strasbourg, Strasbourg, France
| | - Laure Schaeffer
- Institut de Biologie Moléculaire et Cellulaire, "Architecture et Réactivité de l'ARN", Université De Strasbourg, Strasbourg, France
| | - Philippe Hammann
- Institut de Biologie Moléculaire et Cellulaire, Plateforme Protéomique Strasbourg - Esplanade, Université De Strasbourg, Strasbourg, France
| | - Gilbert Eriani
- Institut de Biologie Moléculaire et Cellulaire, "Architecture et Réactivité de l'ARN", Université De Strasbourg, Strasbourg, France
| | - Franck Martin
- Institut de Biologie Moléculaire et Cellulaire, "Architecture et Réactivité de l'ARN", Université De Strasbourg, Strasbourg, France
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Sidrauski C, Tsai JC, Kampmann M, Hearn BR, Vedantham P, Jaishankar P, Sokabe M, Mendez AS, Newton BW, Tang EL, Verschueren E, Johnson JR, Krogan NJ, Fraser CS, Weissman JS, Renslo AR, Walter P. Pharmacological dimerization and activation of the exchange factor eIF2B antagonizes the integrated stress response. eLife 2015; 4:e07314. [PMID: 25875391 PMCID: PMC4426669 DOI: 10.7554/elife.07314] [Citation(s) in RCA: 176] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2015] [Accepted: 04/13/2015] [Indexed: 12/18/2022] Open
Abstract
The general translation initiation factor eIF2 is a major translational control point. Multiple signaling pathways in the integrated stress response phosphorylate eIF2 serine-51, inhibiting nucleotide exchange by eIF2B. ISRIB, a potent drug-like small molecule, renders cells insensitive to eIF2α phosphorylation and enhances cognitive function in rodents by blocking long-term depression. ISRIB was identified in a phenotypic cell-based screen, and its mechanism of action remained unknown. We now report that ISRIB is an activator of eIF2B. Our reporter-based shRNA screen revealed an eIF2B requirement for ISRIB activity. Our results define ISRIB as a symmetric molecule, show ISRIB-mediated stabilization of activated eIF2B dimers, and suggest that eIF2B4 (δ-subunit) contributes to the ISRIB binding site. We also developed new ISRIB analogs, improving its EC50 to 600 pM in cell culture. By modulating eIF2B function, ISRIB promises to be an invaluable tool in proof-of-principle studies aiming to ameliorate cognitive defects resulting from neurodegenerative diseases.
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Affiliation(s)
- Carmela Sidrauski
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States
| | - Jordan C Tsai
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States
| | - Martin Kampmann
- Howard Hughes Medical Institution, University of California, San Francisco, San Francisco, United States
| | - Brian R Hearn
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, United States
| | - Punitha Vedantham
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, United States
| | - Priyadarshini Jaishankar
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, United States
| | - Masaaki Sokabe
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, Davis, United States
| | - Aaron S Mendez
- Howard Hughes Medical Institution, University of California, San Francisco, San Francisco, United States
| | - Billy W Newton
- QB3, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, United States
| | - Edward L Tang
- QB3, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, United States
| | - Erik Verschueren
- QB3, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, United States
| | - Jeffrey R Johnson
- QB3, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, United States
| | - Nevan J Krogan
- QB3, California Institute for Quantitative Biosciences, University of California, San Francisco, San Francisco, United States
| | - Christopher S Fraser
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, Davis, United States
| | - Jonathan S Weissman
- Howard Hughes Medical Institution, University of California, San Francisco, San Francisco, United States
| | - Adam R Renslo
- Department of Pharmaceutical Chemistry, University of California, San Francisco, San Francisco, United States
| | - Peter Walter
- Department of Biochemistry and Biophysics, University of California, San Francisco, San Francisco, United States
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48
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Borgo C, Franchin C, Salizzato V, Cesaro L, Arrigoni G, Matricardi L, Pinna LA, Donella-Deana A. Protein kinase CK2 potentiates translation efficiency by phosphorylating eIF3j at Ser127. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:1693-701. [PMID: 25887626 DOI: 10.1016/j.bbamcr.2015.04.004] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2014] [Revised: 03/17/2015] [Accepted: 04/07/2015] [Indexed: 11/18/2022]
Abstract
In eukaryotic protein synthesis the translation initiation factor 3 (eIF3) is a key player in the recruitment and assembly of the translation initiation machinery. Mammalian eIF3 consists of 13 subunits, including the loosely associated eIF3j subunit that plays a stabilizing role in the eIF3 complex formation and interaction with the 40S ribosomal subunit. By means of both co-immunoprecipitation and mass spectrometry analyses we demonstrate that the protein kinase CK2 interacts with and phosphorylates eIF3j at Ser127. Inhibition of CK2 activity by CX-4945 or down-regulation of the expression of CK2 catalytic subunit by siRNA cause the dissociation of j-subunit from the eIF3 complex as judged from glycerol gradient sedimentation. This finding proves that CK2-phosphorylation of eIF3j is a prerequisite for its association with the eIF3 complex. Expression of Ser127Ala-eIF3j mutant impairs both the interaction of mutated j-subunit with the other eIF3 subunits and the overall protein synthesis. Taken together our data demonstrate that CK2-phosphorylation of eIF3j at Ser127 promotes the assembly of the eIF3 complex, a crucial step in the activation of the translation initiation machinery.
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Affiliation(s)
- Christian Borgo
- Department of Biomedical Sciences, University of Padova, Via U. Bassi 58B, 35131 Padova, Italy; CNR Institute of NeuroSciences, University of Padova, Via U. Bassi 58B, 35131 Padova, Italy
| | - Cinzia Franchin
- Proteomic Center of Padova University, Via G. Orus B2, 35129 Padova, Italy
| | - Valentina Salizzato
- Department of Biomedical Sciences, University of Padova, Via U. Bassi 58B, 35131 Padova, Italy; CNR Institute of NeuroSciences, University of Padova, Via U. Bassi 58B, 35131 Padova, Italy
| | - Luca Cesaro
- Department of Biomedical Sciences, University of Padova, Via U. Bassi 58B, 35131 Padova, Italy; CNR Institute of NeuroSciences, University of Padova, Via U. Bassi 58B, 35131 Padova, Italy
| | - Giorgio Arrigoni
- Proteomic Center of Padova University, Via G. Orus B2, 35129 Padova, Italy
| | - Laura Matricardi
- Venitian Institute of Oncology (IOV-IRCCS), Via Gattamelata 64, 35128 Padova, Italy
| | - Lorenzo A Pinna
- Department of Biomedical Sciences, University of Padova, Via U. Bassi 58B, 35131 Padova, Italy; CNR Institute of NeuroSciences, University of Padova, Via U. Bassi 58B, 35131 Padova, Italy
| | - Arianna Donella-Deana
- Department of Biomedical Sciences, University of Padova, Via U. Bassi 58B, 35131 Padova, Italy; CNR Institute of NeuroSciences, University of Padova, Via U. Bassi 58B, 35131 Padova, Italy.
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49
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Majzoub K, Hafirassou ML, Meignin C, Goto A, Marzi S, Fedorova A, Verdier Y, Vinh J, Hoffmann JA, Martin F, Baumert TF, Schuster C, Imler JL. RACK1 controls IRES-mediated translation of viruses. Cell 2015; 159:1086-1095. [PMID: 25416947 DOI: 10.1016/j.cell.2014.10.041] [Citation(s) in RCA: 128] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2014] [Revised: 09/16/2014] [Accepted: 10/20/2014] [Indexed: 01/31/2023]
Abstract
Fighting viral infections is hampered by the scarcity of viral targets and their variability, resulting in development of resistance. Viruses depend on cellular molecules-which are attractive alternative targets-for their life cycle, provided that they are dispensable for normal cell functions. Using the model organism Drosophila melanogaster, we identify the ribosomal protein RACK1 as a cellular factor required for infection by internal ribosome entry site (IRES)-containing viruses. We further show that RACK1 is an essential determinant for hepatitis C virus translation and infection, indicating that its function is conserved for distantly related human and fly viruses. Inhibition of RACK1 does not affect Drosophila or human cell viability and proliferation, and RACK1-silenced adult flies are viable, indicating that this protein is not essential for general translation. Our findings demonstrate a specific function for RACK1 in selective mRNA translation and uncover a target for the development of broad antiviral intervention.
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Affiliation(s)
- Karim Majzoub
- CNRS UPR9022, Institut de Biologie Moléculaire et Cellulaire, 67000 Strasbourg, France
| | - Mohamed Lamine Hafirassou
- Université de Strasbourg, 67000 Strasbourg, France; Inserm UMR1110, Institut de Recherche sur les Maladies Virales et Hépatiques, 67000 Strasbourg, France
| | - Carine Meignin
- CNRS UPR9022, Institut de Biologie Moléculaire et Cellulaire, 67000 Strasbourg, France; Université de Strasbourg, 67000 Strasbourg, France
| | - Akira Goto
- CNRS UPR9022, Institut de Biologie Moléculaire et Cellulaire, 67000 Strasbourg, France
| | - Stefano Marzi
- CNRS UPR9002, Institut de Biologie Moléculaire et Cellulaire, 67000 Strasbourg, France
| | - Antonina Fedorova
- Université de Strasbourg, 67000 Strasbourg, France; Inserm UMR1110, Institut de Recherche sur les Maladies Virales et Hépatiques, 67000 Strasbourg, France
| | | | - Joëlle Vinh
- USR3149, ESPCI ParisTech, 75005 Paris, France
| | - Jules A Hoffmann
- CNRS UPR9022, Institut de Biologie Moléculaire et Cellulaire, 67000 Strasbourg, France; Université de Strasbourg, 67000 Strasbourg, France; Institut d'Etudes Avancées de l'Université de Strasbourg, 67000 Strasbourg, France
| | - Franck Martin
- CNRS UPR9002, Institut de Biologie Moléculaire et Cellulaire, 67000 Strasbourg, France
| | - Thomas F Baumert
- Université de Strasbourg, 67000 Strasbourg, France; Inserm UMR1110, Institut de Recherche sur les Maladies Virales et Hépatiques, 67000 Strasbourg, France; Institut Hospitalo-Universitaire (IHU), Pôle hépato-digestif, Hôpitaux Universitaires de Strasbourg, 67000 Strasbourg, France
| | - Catherine Schuster
- Université de Strasbourg, 67000 Strasbourg, France; Inserm UMR1110, Institut de Recherche sur les Maladies Virales et Hépatiques, 67000 Strasbourg, France.
| | - Jean-Luc Imler
- CNRS UPR9022, Institut de Biologie Moléculaire et Cellulaire, 67000 Strasbourg, France; Université de Strasbourg, 67000 Strasbourg, France.
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50
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Fraser CS. Quantitative studies of mRNA recruitment to the eukaryotic ribosome. Biochimie 2015; 114:58-71. [PMID: 25742741 DOI: 10.1016/j.biochi.2015.02.017] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 02/20/2015] [Indexed: 12/20/2022]
Abstract
The process of peptide bond synthesis by ribosomes is conserved between species, but the initiation step differs greatly between the three kingdoms of life. This is illustrated by the evolution of roughly an order of magnitude more initiation factor mass found in humans compared with bacteria. Eukaryotic initiation of translation is comprised of a number of sub-steps: (i) recruitment of an mRNA and initiator methionyl-tRNA to the 40S ribosomal subunit; (ii) migration of the 40S subunit along the 5' UTR to locate the initiation codon; and (iii) recruitment of the 60S subunit to form the 80S initiation complex. Although the mechanism and regulation of initiation has been studied for decades, many aspects of the pathway remain unclear. In this review, I will focus discussion on what is known about the mechanism of mRNA selection and its recruitment to the 40S subunit. I will summarize how the 43S preinitiation complex (PIC) is formed and stabilized by interactions between its components. I will discuss what is known about the mechanism of mRNA selection by the eukaryotic initiation factor 4F (eIF4F) complex and how the selected mRNA is recruited to the 43S PIC. The regulation of this process by secondary structure located in the 5' UTR of an mRNA will also be discussed. Finally, I present a possible kinetic model with which to explain the process of mRNA selection and recruitment to the eukaryotic ribosome.
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Affiliation(s)
- Christopher S Fraser
- Department of Molecular and Cellular Biology, College of Biological Sciences, University of California, Davis, CA 95616, USA.
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