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Takallou S, Hajikarimlou M, Al-Gafari M, Wang J, Kazmirchuk TDD, Said KB, Samanfar B, Golshani A. The Involvement of YNR069C in Protein Synthesis in the Baker's Yeast, Saccharomyces cerevisiae. BIOLOGY 2024; 13:138. [PMID: 38534408 DOI: 10.3390/biology13030138] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2023] [Revised: 02/17/2024] [Accepted: 02/19/2024] [Indexed: 03/28/2024]
Abstract
Maintaining translation fidelity is a critical step within the process of gene expression. It requires the involvement of numerous regulatory elements to ensure the synthesis of functional proteins. The efficient termination of protein synthesis can play a crucial role in preserving this fidelity. Here, we report on investigating a protein of unknown function, YNR069C (also known as BSC5), for its activity in the process of translation. We observed a significant increase in the bypass of premature stop codons upon the deletion of YNR069C. Interestingly, the genomic arrangement of this ORF suggests a compatible mode of expression reliant on translational readthrough, incorporating the neighboring open reading frame. We also showed that the deletion of YNR069C results in an increase in the rate of translation. Based on our results, we propose that YNR069C may play a role in translation fidelity, impacting the overall quantity and quality of translation. Our genetic interaction analysis supports our hypothesis, associating the role of YNR069C to the regulation of protein synthesis.
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Affiliation(s)
- Sarah Takallou
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Maryam Hajikarimlou
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Mustafa Al-Gafari
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Jiashu Wang
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Thomas David Daniel Kazmirchuk
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
| | - Kamaledin B Said
- Department of Pathology and Microbiology, College of Medicine, University of Hail, Hail 55476, Saudi Arabia
| | - Bahram Samanfar
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
- Agriculture and Agri-Food Canada, Ottawa Research and Development Centre (ORDC), Ottawa, ON K1A 0C6, Canada
| | - Ashkan Golshani
- Ottawa Institute of Systems Biology, University of Ottawa, Ottawa, ON K1N 6N5, Canada
- Department of Biology, Carleton University, Ottawa, ON K1S 5B6, Canada
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2
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Zhang L, Tang F. Molecular mechanism of Serratia marcescens Bizio infection in Reticulitermes chinensis Snyder based on full-length SMRT transcriptome sequencing. BULLETIN OF ENTOMOLOGICAL RESEARCH 2024:1-13. [PMID: 38328866 DOI: 10.1017/s000748532300072x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2024]
Abstract
Reticulitermes chinensis Snyder is an important pest in forestry and construction and is widely distributed in China. We found that Serratia marcescens Bizio strain SM1 has insecticidal activity to R. chinensis, but the pathogenic mechanism of SM1 to R. chinensis is not clear. Therefore, full-length transcriptome sequencing was performed on R. chinensis infected with SM1 and the control group. A total of 230 differentially expressed genes were identified by comparing SM1 infection group and the control group, among which 103 were downregulated and 127 were upregulated. We found downregulated genes in nine metabolic pathway categories, among which carbohydrate metabolism had the most downregulated genes, followed by energy metabolism and amino acid metabolism. We also found that some downregulated genes were related to pattern recognition receptors, cellular immunity, and humoral immunity, indicating that R. chinensis immunity was negatively affected by SM1 infection. In addition, some genes in signal transduction and genetic information processing pathways were downregulated. In this study, high-throughput full-length transcriptome analysis was used to analyse the pathogenic mechanism of SM1 to R. chinensis. The results of this study provide useful information for exploring the relationship between SM1 and R. chinensis, and provide theoretical support for the future application of SM1 and the prevention and treatment of R. chinensis.
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Affiliation(s)
- Ling Zhang
- Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, People's Republic of China
- College of Forestry, Nanjing Forestry University, Nanjing 210037, People's Republic of China
| | - Fang Tang
- Co-Innovation Center for Sustainable Forestry in Southern China, Nanjing Forestry University, Nanjing 210037, People's Republic of China
- College of Forestry, Nanjing Forestry University, Nanjing 210037, People's Republic of China
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3
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Zhou X, Chen Y, Zhang Z, Miao J, Chen G, Qian Z. Identification of differentially expressed genes, signaling pathways and immune infiltration in postmenopausal osteoporosis by integrated bioinformatics analysis. Heliyon 2024; 10:e23794. [PMID: 38205281 PMCID: PMC10777010 DOI: 10.1016/j.heliyon.2023.e23794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2023] [Revised: 12/12/2023] [Accepted: 12/13/2023] [Indexed: 01/12/2024] Open
Abstract
Background Postmenopausal osteoporosis is a systemic metabolic disorder typified by an imbalance in bone turnover, where bone resorption supersedes bone formation. This imbalance primarily arises from a decline in bone mass induced by estrogen deficiency, and an elevated risk of fractures resulting from degradation of bone microstructure. Despite recognizing these changes, the precise causative factors and potential molecular pathways remain elusive. In this study, we aimed to identify differentially expressed genes (DEGs), associated pathways, and the role of immune infiltration in osteoporosis, leveraging an integrated bioinformatics approach to shed light on potential underlying molecular mechanisms. Methods We retrieved the expression profiles of GSE230665 from the Gene Expression Omnibus database, comprising 15 femur samples, including 12 postmenopausal osteoporosis samples and 3 normal controls. From the aggregated microarray datasets, we derived differentially expressed genes (DEGs) for further bioinformatics analysis. We used WGCNA, analyzed DEGs, PPI, and conducted GO analysis to identify pivotal genes. We then used the CIBERSORT method to explore the degree of immune cell infiltration within femur specimens affected by postmenopausal osteoporosis. To probe into the relationship between pivotal genes and infiltrating immune cells, we conducted correlation analysis. Results We identified a total of 12,204 DEGs. Among these, 12,157 were up-regulated, and 47 were down-regulated. GO and KEGG pathway analyses indicated that these DEGs predominantly targeted cellular protein localization activity and associated signaling pathways. The protein-protein interaction network highlighted four central hub-genes: RPL31, RPL34, EEF1G, and BPTF. Principal component analysis indicated a positive correlation between the expression of these genes and resting NK cells (as per CIBERSORT). In contrast, the expression of RPL31, RPL34, and EEF1G showed a negative correlation with T cells (gamma delta per CIBERSORT). Conclusions Immune infiltration plays a role in the development of osteoporosis.
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Affiliation(s)
- Xiaoli Zhou
- Department of Spine Surgery, Tianjin Hospital, Tianjin University, Tianjin 300211, China
- Department of Toxicology, Tianjin Centers for Disease Control and Prevention, Tianjin 300011, China
| | - Yang Chen
- Department of Spine Surgery, Tianjin Hospital, Tianjin University, Tianjin 300211, China
| | - Zepei Zhang
- Department of Spine Surgery, Tianjin Hospital, Tianjin University, Tianjin 300211, China
| | - Jun Miao
- Department of Spine Surgery, Tianjin Hospital, Tianjin University, Tianjin 300211, China
| | - Guangdong Chen
- Department of Orthopaedics, Cangzhou Central Hospital, Hebei 061001, China
| | - Zhiyong Qian
- Department of Toxicology, Tianjin Centers for Disease Control and Prevention, Tianjin 300011, China
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4
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Rüttermann M, Koci M, Lill P, Geladas ED, Kaschani F, Klink BU, Erdmann R, Gatsogiannis C. Structure of the peroxisomal Pex1/Pex6 ATPase complex bound to a substrate. Nat Commun 2023; 14:5942. [PMID: 37741838 PMCID: PMC10518020 DOI: 10.1038/s41467-023-41640-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2022] [Accepted: 09/12/2023] [Indexed: 09/25/2023] Open
Abstract
The double-ring AAA+ ATPase Pex1/Pex6 is required for peroxisomal receptor recycling and is essential for peroxisome formation. Pex1/Pex6 mutations cause severe peroxisome associated developmental disorders. Despite its pathophysiological importance, mechanistic details of the heterohexamer are not yet available. Here, we report cryoEM structures of Pex1/Pex6 from Saccharomyces cerevisiae, with an endogenous protein substrate trapped in the central pore of the catalytically active second ring (D2). Pairs of Pex1/Pex6(D2) subdomains engage the substrate via a staircase of pore-1 loops with distinct properties. The first ring (D1) is catalytically inactive but undergoes significant conformational changes resulting in alternate widening and narrowing of its pore. These events are fueled by ATP hydrolysis in the D2 ring and disengagement of a "twin-seam" Pex1/Pex6(D2) heterodimer from the staircase. Mechanical forces are propagated in a unique manner along Pex1/Pex6 interfaces that are not available in homo-oligomeric AAA-ATPases. Our structural analysis reveals the mechanisms of how Pex1 and Pex6 coordinate to achieve substrate translocation.
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Affiliation(s)
- Maximilian Rüttermann
- Institute for Medical Physics and Biophysics, University Münster, Münster, Germany
- Center for Soft Nanoscience (SoN), University Münster, Münster, Germany
| | - Michelle Koci
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Pascal Lill
- Institute for Medical Physics and Biophysics, University Münster, Münster, Germany
- Center for Soft Nanoscience (SoN), University Münster, Münster, Germany
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany
| | - Ermis Dionysios Geladas
- Institute for Medical Physics and Biophysics, University Münster, Münster, Germany
- Center for Soft Nanoscience (SoN), University Münster, Münster, Germany
| | - Farnusch Kaschani
- Analytics Core Facility Essen, Center of Medical Biotechnology (ZMB), Faculty of Biology, University of Duisburg-Essen, Essen, Germany
| | - Björn Udo Klink
- Institute for Medical Physics and Biophysics, University Münster, Münster, Germany
- Center for Soft Nanoscience (SoN), University Münster, Münster, Germany
| | - Ralf Erdmann
- Institute for Biochemistry and Pathobiochemistry, Department of Systems Biochemistry, Ruhr-University Bochum, Bochum, Germany
| | - Christos Gatsogiannis
- Institute for Medical Physics and Biophysics, University Münster, Münster, Germany.
- Center for Soft Nanoscience (SoN), University Münster, Münster, Germany.
- Department of Structural Biochemistry, Max Planck Institute of Molecular Physiology, Dortmund, Germany.
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5
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Kišonaitė M, Wild K, Lapouge K, Gesé GV, Kellner N, Hurt E, Sinning I. Structural inventory of cotranslational protein folding by the eukaryotic RAC complex. Nat Struct Mol Biol 2023; 30:670-677. [PMID: 37081320 DOI: 10.1038/s41594-023-00973-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Accepted: 03/20/2023] [Indexed: 04/22/2023]
Abstract
The challenge of nascent chain folding at the ribosome is met by the conserved ribosome-associated complex (RAC), which forms a chaperone triad with the Hsp70 protein Ssb in fungi, and consists of the non-canonical Hsp70 Ssz1 and the J domain protein Zuotin (Zuo1). Here we determine cryo-EM structures of Chaetomium thermophilum RAC bound to 80S ribosomes. RAC adopts two distinct conformations accommodating continuous ribosomal rotation by a flexible lever arm. It is held together by a tight interaction between the Ssz1 substrate-binding domain and the Zuo1 N terminus, and additional contacts between the Ssz1 nucleotide-binding domain and Zuo1 J- and Zuo1 homology domains, which form a rigid unit. The Zuo1 HPD motif conserved in J-proteins is masked in a non-canonical interaction by the Ssz1 nucleotide-binding domain, and allows the positioning of Ssb for activation by Zuo1. Overall, we provide the basis for understanding how RAC cooperates with Ssb in a dynamic nascent chain interaction and protein folding.
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Affiliation(s)
- Miglė Kišonaitė
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Klemens Wild
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Karine Lapouge
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | | | - Nikola Kellner
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Ed Hurt
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany
| | - Irmgard Sinning
- Heidelberg University Biochemistry Center (BZH), Heidelberg, Germany.
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6
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Archaea/eukaryote-specific ribosomal proteins - guardians of a complex structure. Comput Struct Biotechnol J 2023; 21:1249-1261. [PMID: 36817958 PMCID: PMC9932298 DOI: 10.1016/j.csbj.2023.01.037] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2022] [Revised: 01/09/2023] [Accepted: 01/26/2023] [Indexed: 01/29/2023] Open
Abstract
In three domains of life, proteins are synthesized by large ribonucleoprotein particles called ribosomes. All ribosomes are composed of ribosomal RNAs (rRNA) and numerous ribosomal proteins (r-protein). The three-dimensional shape of ribosomes is mainly defined by a tertiary structure of rRNAs. In addition, rRNAs have a major role in decoding the information carried by messenger RNAs and catalyzing the peptide bond formation. R-proteins are essential for shaping the network of interactions that contribute to a various aspects of the protein synthesis machinery, including assembly of ribosomes and interaction of ribosomal subunits. Structural studies have revealed that many key components of ribosomes are conserved in all life domains. Besides the core structure, ribosomes contain domain-specific structural features that include additional r-proteins and extensions of rRNA and r-proteins. This review focuses specifically on those r-proteins that are found only in archaeal and eukaryotic ribosomes. The role of these archaea/eukaryote specific r-proteins in stabilizing the ribosome structure is discussed. Several examples illustrate their functions in the formation of the internal network of ribosomal subunits and interactions between the ribosomal subunits. In addition, the significance of these r-proteins in ribosome biogenesis and protein synthesis is highlighted.
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7
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Wu F, Liu Y, Hu S, Lu C. Ribosomal protein L31 (RPL31) inhibits the proliferation and migration of gastric cancer cells. Heliyon 2023; 9:e13076. [PMID: 36816257 PMCID: PMC9936522 DOI: 10.1016/j.heliyon.2023.e13076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 01/04/2023] [Accepted: 01/16/2023] [Indexed: 01/21/2023] Open
Abstract
Gastric cancer (GC) is a digestive tract malignant tumor and causes the third cancer-related mortality in the world. Aberrant expression of Ribosomal Protein L31 (RPL31) has been reported in several human cancers. The aim of this study was to explore the role and possible biological functions of RPL31 in GC. We firstly employed immunohistochemistry to examine RPL31 expression in tumor and para-cancerous tissues. By lentiviral transfection, we successfully constructed an RPL31-knockdown GC cell model and performed functional validation to reveal the effects of RPL31 on proliferation, apoptosis, cycle, migration, and tumor growth. Our data indicated that RPL31 was abundantly expressed in GC tissues and cell lines (AGS and MGC-803). In addition, RPL31 expression was positively correlated with the extent of tumor infiltrate of GC patients. Functionally, silencing RPL31 in AGS and MGC-803 cells significantly limited the ability of proliferation and migration, promoted cell apoptosis. Consistently, RPL31-knockdown GC cells inhibited the growth of xenografts in mice. Moreover, preliminary analysis on the downstream regulation mechanism revealed that RPL31 functioned as a tumor promoter through targeting JAK-STAT signaling pathway. In conclusion, inhibition of abnormally high expression of RPL31 in GC may be a potential therapeutic strategy for this disease.
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Affiliation(s)
- Fang Wu
- Department of Oncology, The First Affiliated Hospital of Nanchang University. Yongwaizheng Street, No. 17, Nanchang City, Jiangxi Province 330006, China
| | - Yangyang Liu
- Department of Oncology, The First Affiliated Hospital of Nanchang University. Yongwaizheng Street, No. 17, Nanchang City, Jiangxi Province 330006, China
| | - Shenglin Hu
- Department of Internal Medicine, People’s Hospital of Jinan County. Beida Street, No. 5, Jinan City, Jiangxi Province 330699, China
| | - Canrong Lu
- Senior Department of General Surgery, The First Medical Center of Chinese, PLA General Hospital. Fuxin Road, No. 28, Haidian District, Beijing 100853, China,Corresponding author.
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8
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Hu A, Wang Y, Tian J, Chen Z, Chen R, Han X, Chen Y, Liu T, Chen Q. Pan-cancer analysis reveals DDX21 as a potential biomarker for the prognosis of multiple tumor types. Front Oncol 2022; 12:947054. [PMID: 36505822 PMCID: PMC9730287 DOI: 10.3389/fonc.2022.947054] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 10/31/2022] [Indexed: 11/25/2022] Open
Abstract
Background DExD-box helicase 21 (DDX21) is an essential member of the RNA helicase family. DDX21 is involved in the carcinogenesis of various malignancies, but there has been no comprehensive research on its involvement in different types of cancer. Method This study used TCGA, CPTAC, GTEx, GEO, FANTOM5, BioGRID, TIMER2, GEPIA2, cBioPortal, STRING, and Metascape databases and Survival ROC software to evaluate DDX21 gene expression, protein expression, immunohistochemistry, gene mutation, immune infiltration, and protein phosphorylation in 33 TCGA tumor types, as well as the prognostic relationship between DDX21 and different tumors, by survival analysis and similar gene enrichment analysis. Furthermore, Cell Counting Kit-8 (CCK-8) and Transwell studies were employed to assess the effect of DDX21 expression on lung adenocarcinoma (LUAD) cell proliferation and migration. Result The DDX21 gene was highly expressed in most cancers, and overexpression was associated with poor overall survival (OS) and disease-free survival (DFS). DDX21 mutations were most common in uterine corpus endometrial carcinoma (UCEC; >5%), and DDX21 expression was positively correlated with the degree of infiltration of CAF and CD8+ cells in several tumor types. Numerous genes were co-expressed with DDX21. Gene enrichment analysis revealed close links between DDX21, RNA metabolism, and ribosomal protein production. In vitro analysis of LUAD cells showed that DDX21 expression was positively correlated with cell proliferation and migration capacity, consistent with prior bioinformatics studies. Conclusions DDX21 is overexpressed in a variety of cancers, and overexpression in some cancers is associated with poor prognosis. Immune infiltration and DDX21-related gene enrichment analyses indicated that DDX21 may affect cancer development through mechanisms that regulate tumor immunity, RNA metabolism, and ribosomal protein synthesis. This pan-cancer study revealed the prognostic value and the oncogenic role of DDX21.
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Affiliation(s)
- Ankang Hu
- Laboratory Animal Center, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Yonghui Wang
- School of Life Science, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Jiahao Tian
- Clinical Medicine Science, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Zihan Chen
- Cancer Institute, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Renjin Chen
- School of Life Science, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Xufeng Han
- School of Life Science, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Yang Chen
- School of Life Science, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Tingjun Liu
- Laboratory Animal Center, Xuzhou Medical University, Xuzhou, Jiangsu, China
| | - Quangang Chen
- School of Life Science, Xuzhou Medical University, Xuzhou, Jiangsu, China,*Correspondence: Quangang Chen,
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9
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Micic J, Rodríguez-Galán O, Babiano R, Fitzgerald F, Fernández-Fernández J, Zhang Y, Gao N, Woolford JL, de la Cruz J. Ribosomal protein eL39 is important for maturation of the nascent polypeptide exit tunnel and proper protein folding during translation. Nucleic Acids Res 2022; 50:6453-6473. [PMID: 35639884 PMCID: PMC9226512 DOI: 10.1093/nar/gkac366] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 04/04/2022] [Accepted: 05/12/2022] [Indexed: 11/29/2022] Open
Abstract
During translation, nascent polypeptide chains travel from the peptidyl transferase center through the nascent polypeptide exit tunnel (NPET) to emerge from 60S subunits. The NPET includes portions of five of the six 25S/5.8S rRNA domains and ribosomal proteins uL4, uL22, and eL39. Internal loops of uL4 and uL22 form the constriction sites of the NPET and are important for both assembly and function of ribosomes. Here, we investigated the roles of eL39 in tunnel construction, 60S biogenesis, and protein synthesis. We show that eL39 is important for proper protein folding during translation. Consistent with a delay in processing of 27S and 7S pre-rRNAs, eL39 functions in pre-60S assembly during middle nucleolar stages. Our biochemical assays suggest the presence of eL39 in particles at these stages, although it is not visualized in them by cryo-electron microscopy. This indicates that eL39 takes part in assembly even when it is not fully accommodated into the body of pre-60S particles. eL39 is also important for later steps of assembly, rotation of the 5S ribonucleoprotein complex, likely through long range rRNA interactions. Finally, our data strongly suggest the presence of alternative pathways of ribosome assembly, previously observed in the biogenesis of bacterial ribosomal subunits.
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Affiliation(s)
- Jelena Micic
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Olga Rodríguez-Galán
- Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.,Departamento de Genética, Universidad de Sevilla, Seville, Spain
| | - Reyes Babiano
- Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.,Departamento de Genética, Universidad de Sevilla, Seville, Spain
| | - Fiona Fitzgerald
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA, USA
| | - José Fernández-Fernández
- Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.,Departamento de Genética, Universidad de Sevilla, Seville, Spain
| | - Yunyang Zhang
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Joint Centre for Life Sciences, School of Life Sciences, Peking University, Beijing, China
| | - Ning Gao
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Joint Centre for Life Sciences, School of Life Sciences, Peking University, Beijing, China
| | - John L Woolford
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA, USA
| | - Jesús de la Cruz
- Instituto de Biomedicina de Sevilla, Hospital Universitario Virgen del Rocío/CSIC/Universidad de Sevilla, Seville, Spain.,Departamento de Genética, Universidad de Sevilla, Seville, Spain
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10
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Tseng YT, Sung YC, Liu CY, Lo KY. Translation initiation factor eIF4G1 modulates assembly of the polypeptide exit tunnel region in yeast ribosome biogenesis. J Cell Sci 2022; 135:275526. [PMID: 35615984 DOI: 10.1242/jcs.259540] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 05/12/2022] [Indexed: 01/24/2023] Open
Abstract
eIF4G is an important eukaryotic translation initiation factor. In this study, eIF4G1, one of the eIF4G isoforms, was shown to directly participate in biogenesis of the large (60S) ribosomal subunit in Saccharomyces cerevisiae cells. Mutation of eIF4G1 decreased the amount 60S ribosomal subunits significantly. The C-terminal fragment of eIF4G1 could complement the function in 60S biogenesis. Analyses of its purified complex with mass spectrometry indicated that eIF4G1 associated with the pre-60S form directly. Strong genetic and direct protein-protein interactions were observed between eIF4G1 and Ssf1 protein. Upon deletion of eIF4G1, Ssf1, Rrp15, Rrp14 and Mak16 were abnormally retained on the pre-60S complex. This purturbed the loading of Arx1 and eL31 at the polypeptide exit tunnel (PET) site and the transition to a Nog2 complex. Our data indicate that eIF4G1 is important in facilitating PET maturation and 27S processing correctly. This article has an associated First Person interview with the first author of the paper.
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Affiliation(s)
- Yun-Ting Tseng
- Department of Agricultural Chemistry, College of Bioresources and Agriculture, National Taiwan University, Taipei 10617, Taiwan
| | - Yu-Cheng Sung
- Department of Agricultural Chemistry, College of Bioresources and Agriculture, National Taiwan University, Taipei 10617, Taiwan
| | - Ching-Yu Liu
- Department of Agricultural Chemistry, College of Bioresources and Agriculture, National Taiwan University, Taipei 10617, Taiwan
| | - Kai-Yin Lo
- Department of Agricultural Chemistry, College of Bioresources and Agriculture, National Taiwan University, Taipei 10617, Taiwan
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11
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Structural remodeling of ribosome associated Hsp40-Hsp70 chaperones during co-translational folding. Nat Commun 2022; 13:3410. [PMID: 35701497 PMCID: PMC9197937 DOI: 10.1038/s41467-022-31127-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2021] [Accepted: 06/02/2022] [Indexed: 11/16/2022] Open
Abstract
Ribosome associated complex (RAC), an obligate heterodimer of HSP40 and HSP70 (Zuo1 and Ssz1 in yeast), is conserved in eukaryotes and functions as co-chaperone for another HSP70 (Ssb1/2 in yeast) to facilitate co-translational folding of nascent polypeptides. Many mechanistic details, such as the coordination of one HSP40 with two HSP70s and the dynamic interplay between RAC-Ssb and growing nascent chains, remain unclear. Here, we report three sets of structures of RAC-containing ribosomal complexes isolated from Saccharomyces cerevisiae. Structural analyses indicate that RAC on the nascent-chain-free ribosome is in an autoinhibited conformation, and in the presence of a nascent chain at the peptide tunnel exit (PTE), RAC undergoes large-scale structural remodeling to make Zuo1 J-Domain more accessible to Ssb. Our data also suggest a role of Zuo1 in orienting Ssb-SBD proximal to the PTE for easy capture of the substrate. Altogether, in accordance with previous data, our work suggests a sequence of structural remodeling events for RAC-Ssb during co-translational folding, triggered by the binding and passage of growing nascent chain from one to another. Ribosome associated complex (RAC)- HSP70 (Ssb in yeast) is a eukaryotic chaperone system involved in co-translational folding. Here, authors report structures of RAC-containing ribosomal complexes, which suggest a working model for the dynamic actions of RAC-Ssb during the process.
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12
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Silistre H, Raoux-Barbot D, Mancinelli F, Sangouard F, Dupin A, Belyy A, Deruelle V, Renault L, Ladant D, Touqui L, Mechold U. Prevalence of ExoY Activity in Pseudomonas aeruginosa Reference Panel Strains and Impact on Cytotoxicity in Epithelial Cells. Front Microbiol 2021; 12:666097. [PMID: 34675890 PMCID: PMC8524455 DOI: 10.3389/fmicb.2021.666097] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Accepted: 07/30/2021] [Indexed: 11/13/2022] Open
Abstract
ExoY is among the effectors that are injected by the type III secretion system (T3SS) of Pseudomonas aeruginosa into host cells. Inside eukaryotic cells, ExoY interacts with F-actin, which stimulates its potent nucleotidyl cyclase activity to produce cyclic nucleotide monophosphates (cNMPs). ExoY has broad substrate specificity with GTP as a preferential substrate in vitro. How ExoY contributes to the virulence of P. aeruginosa remains largely unknown. Here, we examined the prevalence of active ExoY among strains from the international P. aeruginosa reference panel, a collection of strains that includes environmental and clinical isolates, commonly used laboratory strains, and sequential clonal isolates from cystic fibrosis (CF) patients and thus represents the large diversity of this bacterial species. The ability to secrete active ExoY was determined by measuring the F-actin stimulated guanylate cyclase (GC) activity in bacterial culture supernatants. We found an overall ExoY activity prevalence of about 60% among the 40 examined strains with no significant difference between CF and non-CF isolates. In parallel, we used cellular infection models of human lung epithelial cells to compare the cytotoxic effects of isogenic reference strains expressing active ExoY or lacking the exoY gene. We found that P. aeruginosa strains lacking ExoY were in fact more cytotoxic to the epithelial cells than those secreting active ExoY. This suggests that under certain conditions, ExoY might partly alleviate the cytotoxic effects of other virulence factors of P. aeruginosa.
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Affiliation(s)
- Hazel Silistre
- Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie, Institut Pasteur, CNRS UMR 3528, Paris, France
| | - Dorothée Raoux-Barbot
- Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie, Institut Pasteur, CNRS UMR 3528, Paris, France
| | - Federica Mancinelli
- Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie, Institut Pasteur, CNRS UMR 3528, Paris, France
| | - Flora Sangouard
- Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie, Institut Pasteur, CNRS UMR 3528, Paris, France
| | - Alice Dupin
- Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie, Institut Pasteur, CNRS UMR 3528, Paris, France
| | - Alexander Belyy
- Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie, Institut Pasteur, CNRS UMR 3528, Paris, France
| | - Vincent Deruelle
- Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie, Institut Pasteur, CNRS UMR 3528, Paris, France
| | - Louis Renault
- Université Paris-Saclay, CEA, CNRS, Institute for Integrative Biology of the Cell (I2BC), Gif-sur-Yvette, France
| | - Daniel Ladant
- Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie, Institut Pasteur, CNRS UMR 3528, Paris, France
| | - Lhousseine Touqui
- Mucoviscidose: Physiopathologie et Phénogénomique, Centre de Recherche Saint-Antoine (CRSA), INSERM UMR S 938, Sorbonne Université, Paris, France.,Mucoviscidose et Bronchopathies Chroniques, Département Santé Globale, Institute Pasteur, Paris, France
| | - Undine Mechold
- Unité de Biochimie des Interactions Macromoléculaires, Département de Biologie Structurale et Chimie, Institut Pasteur, CNRS UMR 3528, Paris, France
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13
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Zou Q, Qi H. Deletion of ribosomal paralogs Rpl39 and Rpl39l compromises cell proliferation via protein synthesis and mitochondrial activity. Int J Biochem Cell Biol 2021; 139:106070. [PMID: 34428590 DOI: 10.1016/j.biocel.2021.106070] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2021] [Revised: 07/25/2021] [Accepted: 08/19/2021] [Indexed: 11/15/2022]
Abstract
Accumulating evidences suggest that the composition and functional roles of ribosomes are heterogeneous in cells, partly due to the temporal-spatial expression of paralogous ribosomal proteins (RPs), of which functional relationships remain largely unexplored. In mouse, the X chromosome-linked RPL39 and its male germline specific paralog RPL39L are thought to express mutually exclusively due to the meiotic sex chromosome inactivation, hinders the understanding of their functional relationships. In the present study, we investigated the expression and functional relations of Rpl39 and Rpl39l in a proliferative mouse cell line, in which both genes are expressed simultaneously, with the expression level of Rpl39 higher than that of Rpl39l. Disruption of Rpl39 via CRISPR/Cas9 method caused decreased cell proliferation, nascent protein synthesis and altered mitochondrial functions, whereas double mutations of Rpl39 and Rpl39l augmented these phenotypes, suggesting that both RPs contribute to the cellular physiology. Consistently, overexpression of Rpl39, Rpl39l or an alanine mutant of RPL39, rescued cell proliferation similarly in Rpl39-/-::Rpl39l-/- dual gene null cells. Deletion of Rpl39l induced compensatory expression of Rpl39, rendering the deleterious effects of Rpl39l mutation. Supporting this, Rpl39l mutation was more detrimental to cells under a low serum condition, under which the compensatory expression of Rpl39 was inhibited. Moreover, the low serum condition induced expression of both genes, suggesting that they possess stress responsive roles. Taken together, these data indicate that both RPL39 and RPL39L influence cell proliferation via protein synthesis and mitochondrial functions, suggesting a link between protein translation and cellular metabolism through these ribosomal protein paralogs.
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Affiliation(s)
- Qianxing Zou
- CAS Key Laboratory of Regenerative Biology; Center for Cell Lineage and Development; Guangdong Provincial Key Laboratory of Stem Cell and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Huayu Qi
- CAS Key Laboratory of Regenerative Biology; Center for Cell Lineage and Development; Guangdong Provincial Key Laboratory of Stem Cell and Regenerative Medicine, Guangzhou Institutes of Biomedicine and Health, Chinese Academy of Sciences, Guangzhou 510530, China; University of Chinese Academy of Sciences, Beijing 100049, China.
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14
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A role for the ribosome-associated complex in activation of the IRE1 branch of UPR. Cell Rep 2021; 35:109217. [PMID: 34107246 DOI: 10.1016/j.celrep.2021.109217] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 03/31/2021] [Accepted: 05/13/2021] [Indexed: 12/11/2022] Open
Abstract
The ubiquitous ribosome-associated complex (RAC) is a chaperone that spans ribosomes, making contacts near both the polypeptide exit tunnel and the decoding center, a position prime for sensing and coordinating translation and folding. Loss of RAC is known to result in growth defects and sensitization to translational and osmotic stresses. However, the physiological substrates of RAC and the mechanism(s) by which RAC is involved in responding to specific stresses in higher eukaryotes remain obscure. The data presented here uncover an essential function of mammalian RAC in the unfolded protein response (UPR). Knockdown of RAC sensitizes mammalian cells to endoplasmic reticulum (ER) stress and selectively interferes with IRE1 branch activation. Higher-order oligomerization of the inositol-requiring enzyme 1α (IRE1α) kinase/endoribonuclease depends upon RAC. These results reveal a surveillance function for RAC in the UPR, as follows: modulating IRE1α clustering as required for endonuclease activation and splicing of the substrate Xbp1 mRNA.
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15
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Ward T, Tai W, Morton S, Impens F, Van Damme P, Van Haver D, Timmerman E, Venturini G, Zhang K, Jang MY, Willcox JAL, Haghighi A, Gelb BD, Chung WK, Goldmuntz E, Porter GA, Lifton RP, Brueckner M, Yost HJ, Bruneau BG, Gorham J, Kim Y, Pereira A, Homsy J, Benson CC, DePalma SR, Varland S, Chen CS, Arnesen T, Gevaert K, Seidman C, Seidman JG. Mechanisms of Congenital Heart Disease Caused by NAA15 Haploinsufficiency. Circ Res 2021; 128:1156-1169. [PMID: 33557580 PMCID: PMC8048381 DOI: 10.1161/circresaha.120.316966] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
[Figure: see text].
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Affiliation(s)
- Tarsha Ward
- Genetics (T.W., W.T., S.M., G.V., M.Y.J., J.A.L.W., A.H., J.G., Y.K., A.P., J.H., C.C.B., S.R.D., C.S., J.G.S.), Harvard Medical School
| | - Warren Tai
- Genetics (T.W., W.T., S.M., G.V., M.Y.J., J.A.L.W., A.H., J.G., Y.K., A.P., J.H., C.C.B., S.R.D., C.S., J.G.S.), Harvard Medical School
| | - Sarah Morton
- Genetics (T.W., W.T., S.M., G.V., M.Y.J., J.A.L.W., A.H., J.G., Y.K., A.P., J.H., C.C.B., S.R.D., C.S., J.G.S.), Harvard Medical School.,Division of Newborn Medicine, Boston Children's Hospital (S.M.)
| | - Francis Impens
- VIB Center for Medical Biotechnology, B-9000 Ghent, Belgium (F.I., D.V.H., E.T., K.G.).,VIB Proteomics Core, B-9000 Ghent, Belgium (F.I., D.V.H., E.T.).,Biomolecular Medicine (F.I., D.V.H., E.T., K.G.), Ghent University, B-9000 Ghent, Belgium
| | - Petra Van Damme
- Biochemistry and Microbiology (P.V.D.), Ghent University, B-9000 Ghent, Belgium
| | - Delphi Van Haver
- VIB Center for Medical Biotechnology, B-9000 Ghent, Belgium (F.I., D.V.H., E.T., K.G.).,VIB Proteomics Core, B-9000 Ghent, Belgium (F.I., D.V.H., E.T.).,Biomolecular Medicine (F.I., D.V.H., E.T., K.G.), Ghent University, B-9000 Ghent, Belgium
| | - Evy Timmerman
- VIB Center for Medical Biotechnology, B-9000 Ghent, Belgium (F.I., D.V.H., E.T., K.G.).,VIB Proteomics Core, B-9000 Ghent, Belgium (F.I., D.V.H., E.T.).,Biomolecular Medicine (F.I., D.V.H., E.T., K.G.), Ghent University, B-9000 Ghent, Belgium
| | - Gabriela Venturini
- Genetics (T.W., W.T., S.M., G.V., M.Y.J., J.A.L.W., A.H., J.G., Y.K., A.P., J.H., C.C.B., S.R.D., C.S., J.G.S.), Harvard Medical School.,University of Sao Paulo (G.V.)
| | - Kehan Zhang
- Biomedical Engineering, Boston University, MA (K.Z., C.S.C.).,The Wyss Institute for Biologically Inspired Engineering at Harvard University, Boston, MA (K.Z., C.S.C.)
| | - Min Young Jang
- Genetics (T.W., W.T., S.M., G.V., M.Y.J., J.A.L.W., A.H., J.G., Y.K., A.P., J.H., C.C.B., S.R.D., C.S., J.G.S.), Harvard Medical School
| | - Jon A L Willcox
- Genetics (T.W., W.T., S.M., G.V., M.Y.J., J.A.L.W., A.H., J.G., Y.K., A.P., J.H., C.C.B., S.R.D., C.S., J.G.S.), Harvard Medical School
| | - Alireza Haghighi
- Genetics (T.W., W.T., S.M., G.V., M.Y.J., J.A.L.W., A.H., J.G., Y.K., A.P., J.H., C.C.B., S.R.D., C.S., J.G.S.), Harvard Medical School.,Howard Hughes Medical Institute (A.H., C.S.), Harvard Medical School.,Medicine, Brigham and Women's Hospital (A.H., C.S.)
| | - Bruce D Gelb
- Genetics and Genomic Sciences, Icahn School of Medicine at Mount Sinai, New York (B.D.G.)
| | - Wendy K Chung
- Pediatrics and Medicine, Columbia University Medical Center, New York (W.K.C.)
| | - Elizabeth Goldmuntz
- Cardiology, Children's Hospital of Philadelphia, Department of Pediatrics, The Perelman School of Medicine, University of Pennsylvania, Philadelphia (E.G.)
| | | | - Richard P Lifton
- Genetics, Yale University School of Medicine, New Haven (R.P.L., M.B.).,Laboratory of Human Genetics and Genomics, Rockefeller University, New York (R.P.L.)
| | - Martina Brueckner
- Genetics, Yale University School of Medicine, New Haven (R.P.L., M.B.).,Pediatrics, Yale University School of Medicine, New Haven (M.B.)
| | - H Joseph Yost
- Molecular Medicine Program, University of Utah, Salt Lake City (H.J.Y.)
| | | | - Joshua Gorham
- Genetics (T.W., W.T., S.M., G.V., M.Y.J., J.A.L.W., A.H., J.G., Y.K., A.P., J.H., C.C.B., S.R.D., C.S., J.G.S.), Harvard Medical School
| | - Yuri Kim
- Genetics (T.W., W.T., S.M., G.V., M.Y.J., J.A.L.W., A.H., J.G., Y.K., A.P., J.H., C.C.B., S.R.D., C.S., J.G.S.), Harvard Medical School.,Division of Cardiovascular Medicine, Brigham and Women's Hospital (Y.K.)
| | - Alexandre Pereira
- Genetics (T.W., W.T., S.M., G.V., M.Y.J., J.A.L.W., A.H., J.G., Y.K., A.P., J.H., C.C.B., S.R.D., C.S., J.G.S.), Harvard Medical School
| | - Jason Homsy
- Genetics (T.W., W.T., S.M., G.V., M.Y.J., J.A.L.W., A.H., J.G., Y.K., A.P., J.H., C.C.B., S.R.D., C.S., J.G.S.), Harvard Medical School
| | - Craig C Benson
- Genetics (T.W., W.T., S.M., G.V., M.Y.J., J.A.L.W., A.H., J.G., Y.K., A.P., J.H., C.C.B., S.R.D., C.S., J.G.S.), Harvard Medical School
| | - Steven R DePalma
- Genetics (T.W., W.T., S.M., G.V., M.Y.J., J.A.L.W., A.H., J.G., Y.K., A.P., J.H., C.C.B., S.R.D., C.S., J.G.S.), Harvard Medical School
| | - Sylvia Varland
- Biomedicine (S.V., T.A.), University of Bergen, N-5020 Bergen, Norway.,Biological Sciences (S.V., T.A.), University of Bergen, N-5020 Bergen, Norway.,Donnelly Centre for Cellular and Biomolecular Research, Toronto, Canada (S.V.)
| | - Christopher S Chen
- Biomedical Engineering, Boston University, MA (K.Z., C.S.C.).,The Wyss Institute for Biologically Inspired Engineering at Harvard University, Boston, MA (K.Z., C.S.C.)
| | - Thomas Arnesen
- Biomedicine (S.V., T.A.), University of Bergen, N-5020 Bergen, Norway.,Biological Sciences (S.V., T.A.), University of Bergen, N-5020 Bergen, Norway.,Surgery, Haukeland University Hospital, N-5021 Bergen, Norway (T.A.)
| | - Kris Gevaert
- Biomolecular Medicine (F.I., D.V.H., E.T., K.G.), Ghent University, B-9000 Ghent, Belgium
| | - Christine Seidman
- Genetics (T.W., W.T., S.M., G.V., M.Y.J., J.A.L.W., A.H., J.G., Y.K., A.P., J.H., C.C.B., S.R.D., C.S., J.G.S.), Harvard Medical School.,Howard Hughes Medical Institute (A.H., C.S.), Harvard Medical School.,Medicine, Brigham and Women's Hospital (A.H., C.S.)
| | - J G Seidman
- Genetics (T.W., W.T., S.M., G.V., M.Y.J., J.A.L.W., A.H., J.G., Y.K., A.P., J.H., C.C.B., S.R.D., C.S., J.G.S.), Harvard Medical School
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16
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Ghosh A, Shcherbik N. Cooperativity between the Ribosome-Associated Chaperone Ssb/RAC and the Ubiquitin Ligase Ltn1 in Ubiquitination of Nascent Polypeptides. Int J Mol Sci 2020; 21:ijms21186815. [PMID: 32957466 PMCID: PMC7554835 DOI: 10.3390/ijms21186815] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Revised: 09/12/2020] [Accepted: 09/14/2020] [Indexed: 11/25/2022] Open
Abstract
Eukaryotic cells have evolved multiple mechanisms to detect and eliminate aberrant polypeptides. Co-translational protein surveillance systems play an important role in these mechanisms. These systems include ribosome-associated protein quality control (RQC) that detects aberrant nascent chains stalled on ribosomes and promotes their ubiquitination and degradation by the proteasome, and ribosome-associated chaperone Ssb/RAC, which ensures correct nascent chain folding. Despite the known function of RQC and Ssb/ribosome-associated complex (RAC) in monitoring the quality of newly generated polypeptides, whether they cooperate during initial stages of protein synthesis remains unexplored. Here, we provide evidence that Ssb/RAC and the ubiquitin ligase Ltn1, the major component of RQC, display genetic and functional cooperativity. Overexpression of Ltn1 rescues growth suppression of the yeast strain-bearing deletions of SSB genes during proteotoxic stress. Moreover, Ssb/RAC promotes Ltn1-dependent ubiquitination of nascent chains associated with 80S ribosomal particles but not with translating ribosomes. Consistent with this finding, quantitative western blot analysis revealed lower levels of Ltn1 associated with 80S ribosomes and with free 60S ribosomal subunits in the absence of Ssb/RAC. We propose a mechanism in which Ssb/RAC facilitates recruitment of Ltn1 to ribosomes, likely by detecting aberrations in nascent chains and leading to their ubiquitination and degradation.
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17
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The ribosome-associated complex RAC serves in a relay that directs nascent chains to Ssb. Nat Commun 2020; 11:1504. [PMID: 32198371 PMCID: PMC7083937 DOI: 10.1038/s41467-020-15313-w] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2019] [Accepted: 03/03/2020] [Indexed: 11/21/2022] Open
Abstract
The conserved ribosome-associated complex (RAC) consisting of Zuo1 (Hsp40) and Ssz1 (non-canonical Hsp70) acts together with the ribosome-bound Hsp70 chaperone Ssb in de novo protein folding at the ribosomal tunnel exit. Current models suggest that the function of Ssz1 is confined to the support of Zuo1, however, it is not known whether RAC by itself serves as a chaperone for nascent chains. Here we show that, via its rudimentary substrate binding domain (SBD), Ssz1 directly binds to emerging nascent chains prior to Ssb. Structural and biochemical analyses identify a conserved LP-motif at the Zuo1 N-terminus forming a polyproline-II helix, which binds to the Ssz1-SBD as a pseudo-substrate. The LP-motif competes with nascent chain binding to the Ssz1-SBD and modulates nascent chain transfer. The combined data indicate that Ssz1 is an active chaperone optimized for transient, low-affinity substrate binding, which ensures the flux of nascent chains through RAC/Ssb. The ribosome-associated complex (RAC), which contains the Hsp40 protein Zuo1 and the non-canonical Hsp70 protein Ssz1 forms a chaperone triad with the fungal-specific Hsp70 protein Ssb. Here the authors combine X-ray crystallography, crosslinking and biochemical experiments and present the structure of the Zuo1 N-terminus bound to Ssz1 and demonstrate that Ssz1 is an active chaperone for nascent chains.
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18
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Gribling-Burrer AS, Chiabudini M, Zhang Y, Qiu Z, Scazzari M, Wölfle T, Wohlwend D, Rospert S. A dual role of the ribosome-bound chaperones RAC/Ssb in maintaining the fidelity of translation termination. Nucleic Acids Res 2020; 47:7018-7034. [PMID: 31114879 PMCID: PMC6648330 DOI: 10.1093/nar/gkz334] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Revised: 04/05/2019] [Accepted: 04/25/2019] [Indexed: 11/22/2022] Open
Abstract
The yeast ribosome-associated complex RAC and the Hsp70 homolog Ssb are anchored to the ribosome and together act as chaperones for the folding and co-translational assembly of nascent polypeptides. In addition, the RAC/Ssb system plays a crucial role in maintaining the fidelity of translation termination; however, the latter function is poorly understood. Here we show that the RAC/Ssb system promotes the fidelity of translation termination via two distinct mechanisms. First, via direct contacts with the ribosome and the nascent chain, RAC/Ssb facilitates the translation of stalling-prone poly-AAG/A sequences encoding for polylysine segments. Impairment of this function leads to enhanced ribosome stalling and to premature nascent polypeptide release at AAG/A codons. Second, RAC/Ssb is required for the assembly of fully functional ribosomes. When RAC/Ssb is absent, ribosome biogenesis is hampered such that core ribosomal particles are structurally altered at the decoding and peptidyl transferase centers. As a result, ribosomes assembled in the absence of RAC/Ssb bind to the aminoglycoside paromomycin with high affinity (KD = 76.6 nM) and display impaired discrimination between stop codons and sense codons. The combined data shed light on the multiple mechanisms by which the RAC/Ssb system promotes unimpeded biogenesis of newly synthesized polypeptides.
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Affiliation(s)
- Anne-Sophie Gribling-Burrer
- Institute of Biochemistry and Molecular Biology, ZBMZ, Medical Faculty, University of Freiburg, D-79104 Freiburg, Germany
| | - Marco Chiabudini
- Institute of Biochemistry and Molecular Biology, ZBMZ, Medical Faculty, University of Freiburg, D-79104 Freiburg, Germany
| | - Ying Zhang
- Institute of Biochemistry and Molecular Biology, ZBMZ, Medical Faculty, University of Freiburg, D-79104 Freiburg, Germany
| | - Zonghao Qiu
- Institute of Biochemistry and Molecular Biology, ZBMZ, Medical Faculty, University of Freiburg, D-79104 Freiburg, Germany
| | - Mario Scazzari
- Institute of Biochemistry and Molecular Biology, ZBMZ, Medical Faculty, University of Freiburg, D-79104 Freiburg, Germany
| | - Tina Wölfle
- Institute of Biochemistry and Molecular Biology, ZBMZ, Medical Faculty, University of Freiburg, D-79104 Freiburg, Germany
| | - Daniel Wohlwend
- Institute of Biochemistry, Chemical and Pharmaceutical Faculty, University of Freiburg, D-79104 Freiburg, Germany
| | - Sabine Rospert
- Institute of Biochemistry and Molecular Biology, ZBMZ, Medical Faculty, University of Freiburg, D-79104 Freiburg, Germany.,BIOSS Centre for Biological Signaling Studies, University of Freiburg, D-79104 Freiburg, Germany
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19
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Abstract
In the past 25 years, genetic and biochemical analyses of ribosome assembly in yeast have identified most of the factors that participate in this complex pathway and have generated models for the mechanisms driving the assembly. More recently, the publication of numerous cryo-electron microscopy structures of yeast ribosome assembly intermediates has provided near-atomic resolution snapshots of ribosome precursor particles. Satisfyingly, these structural data support the genetic and biochemical models and provide additional mechanistic insight into ribosome assembly. In this Review, we discuss the mechanisms of assembly of the yeast small ribosomal subunit and large ribosomal subunit in the nucleolus, nucleus and cytoplasm. Particular emphasis is placed on concepts such as the mechanisms of RNA compaction, the functions of molecular switches and molecular mimicry, the irreversibility of assembly checkpoints and the roles of structural and functional proofreading of pre-ribosomal particles.
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20
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Deuerling E, Gamerdinger M, Kreft SG. Chaperone Interactions at the Ribosome. Cold Spring Harb Perspect Biol 2019; 11:cshperspect.a033977. [PMID: 30833456 DOI: 10.1101/cshperspect.a033977] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
The continuous refreshment of the proteome is critical to maintain protein homeostasis and to adapt cells to changing conditions. Thus, de novo protein biogenesis by ribosomes is vitally important to every cellular system. This process is delicate and error-prone and requires, besides cytosolic chaperones, the guidance by a specialized set of molecular chaperones that bind transiently to the translation machinery and the nascent protein to support early folding events and to regulate cotranslational protein transport. These chaperones include the bacterial trigger factor (TF), the archaeal and eukaryotic nascent polypeptide-associated complex (NAC), and the eukaryotic ribosome-associated complex (RAC). This review focuses on the structures, functions, and substrates of these ribosome-associated chaperones and highlights the most recent findings about their potential mechanisms of action.
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Affiliation(s)
- Elke Deuerling
- Molecular Microbiology, Department of Biology, University of Konstanz, 78464 Konstanz, Germany
| | - Martin Gamerdinger
- Molecular Microbiology, Department of Biology, University of Konstanz, 78464 Konstanz, Germany
| | - Stefan G Kreft
- Molecular Microbiology, Department of Biology, University of Konstanz, 78464 Konstanz, Germany
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21
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Kramer G, Shiber A, Bukau B. Mechanisms of Cotranslational Maturation of Newly Synthesized Proteins. Annu Rev Biochem 2019; 88:337-364. [DOI: 10.1146/annurev-biochem-013118-111717] [Citation(s) in RCA: 98] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The timely production of functional proteins is of critical importance for the biological activity of cells. To reach the functional state, newly synthesized polypeptides have to become enzymatically processed, folded, and assembled into oligomeric complexes and, for noncytosolic proteins, translocated across membranes. Key activities of these processes occur cotranslationally, assisted by a network of machineries that transiently engage nascent polypeptides at distinct phases of translation. The sequence of events is tuned by intrinsic features of the nascent polypeptides and timely association of factors with the translating ribosome. Considering the dynamics of translation, the heterogeneity of cellular proteins, and the diversity of interaction partners, it is a major cellular achievement that these processes are temporally and spatially so precisely coordinated, minimizing the generation of damaged proteins. This review summarizes the current progress we have made toward a comprehensive understanding of the cotranslational interactions of nascent chains, which pave the way to their functional state.
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Affiliation(s)
- Günter Kramer
- Center for Molecular Biology of Heidelberg University (ZMBH) and German Cancer Research Center (DKFZ), DKFZ-ZMBH Alliance, D-69120 Heidelberg, Germany;,
| | - Ayala Shiber
- Center for Molecular Biology of Heidelberg University (ZMBH) and German Cancer Research Center (DKFZ), DKFZ-ZMBH Alliance, D-69120 Heidelberg, Germany;,
| | - Bernd Bukau
- Center for Molecular Biology of Heidelberg University (ZMBH) and German Cancer Research Center (DKFZ), DKFZ-ZMBH Alliance, D-69120 Heidelberg, Germany;,
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22
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Structure and evolution of the 4-helix bundle domain of Zuotin, a J-domain protein co-chaperone of Hsp70. PLoS One 2019; 14:e0217098. [PMID: 31091298 PMCID: PMC6519820 DOI: 10.1371/journal.pone.0217098] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Accepted: 05/03/2019] [Indexed: 11/28/2022] Open
Abstract
The J-domain protein Zuotin is a multi-domain eukaryotic Hsp70 co-chaperone. Though it is primarily ribosome-associated, positioned at the exit of the 60S subunit tunnel where it promotes folding of nascent polypeptide chains, Zuotin also has off-ribosome functions. Domains of Zuotin needed for 60S association and interaction with Hsp70 are conserved in eukaryotes. However, whether the 4-helix bundle (4HB) domain is conserved remains an open question. We undertook evolutionary and structural approaches to clarify this issue. We found that the 4HB segment of human Zuotin also forms a bundle of 4 helices. The positive charge of Helix I, which in Saccharomyces cerevisiae is responsible for interaction with the 40S subunit, is particularly conserved. However, the C-termini of fungal and human 4HBs are not similar. In fungi the C-terminal segment forms a plug that folds back into the bundle; in S. cerevisiae it plays an important role in bundle stability and, off the ribosome, in transcriptional activation. In human, C-terminal helix IV of the 4HB is extended, protruding from the bundle. This extension serves as a linker to the regulatory SANT domains, which are present in animals, plants and protists, but not fungi. Further analysis of Zuotin sequences revealed that the plug likely arose as a result of genomic rearrangement upon SANT domain loss early in the fungal lineage. In the lineage leading to S. cerevisiae, the 4HB was subjected to positive selection with the plug becoming increasingly hydrophobic. Eventually, these hydrophobic plug residues were coopted for a novel regulatory function—activation of a recently emerged transcription factor, Pdr1. Our data suggests that Zuotin evolved off-ribosome functions twice—once involving SANT domains, then later in fungi, after SANT domain loss, by coopting the hydrophobic plug. Zuotin serves as an example of complex intertwining of molecular chaperone function and cell regulation.
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23
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Karamyshev AL, Karamysheva ZN. Lost in Translation: Ribosome-Associated mRNA and Protein Quality Controls. Front Genet 2018; 9:431. [PMID: 30337940 PMCID: PMC6180196 DOI: 10.3389/fgene.2018.00431] [Citation(s) in RCA: 73] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Accepted: 09/11/2018] [Indexed: 12/15/2022] Open
Abstract
Aberrant, misfolded, and mislocalized proteins are often toxic to cells and result in many human diseases. All proteins and their mRNA templates are subject to quality control. There are several distinct mechanisms that control the quality of mRNAs and proteins during translation at the ribosome. mRNA quality control systems, nonsense-mediated decay, non-stop decay, and no-go decay detect premature stop codons, the absence of a natural stop codon, and stalled ribosomes in translation, respectively, and degrade their mRNAs. Defective truncated polypeptide nascent chains generated from faulty mRNAs are degraded by ribosome-associated protein quality control pathways. Regulation of aberrant protein production, a novel pathway, senses aberrant proteins by monitoring the status of nascent chain interactions during translation and triggers degradation of their mRNA. Here, we review the current progress in understanding of the molecular mechanisms of mRNA and protein quality controls at the ribosome during translation.
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Affiliation(s)
- Andrey L Karamyshev
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, TX, United States
| | - Zemfira N Karamysheva
- Department of Biological Sciences, Texas Tech University, Lubbock, TX, United States
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24
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Zhang YH, Huang T, Chen L, Xu Y, Hu Y, Hu LD, Cai Y, Kong X. Identifying and analyzing different cancer subtypes using RNA-seq data of blood platelets. Oncotarget 2017; 8:87494-87511. [PMID: 29152097 PMCID: PMC5675649 DOI: 10.18632/oncotarget.20903] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 08/16/2017] [Indexed: 12/11/2022] Open
Abstract
Detection and diagnosis of cancer are especially important for early prevention and effective treatments. Traditional methods of cancer detection are usually time-consuming and expensive. Liquid biopsy, a newly proposed noninvasive detection approach, can promote the accuracy and decrease the cost of detection according to a personalized expression profile. However, few studies have been performed to analyze this type of data, which can promote more effective methods for detection of different cancer subtypes. In this study, we applied some reliable machine learning algorithms to analyze data retrieved from patients who had one of six cancer subtypes (breast cancer, colorectal cancer, glioblastoma, hepatobiliary cancer, lung cancer and pancreatic cancer) as well as healthy persons. Quantitative gene expression profiles were used to encode each sample. Then, they were analyzed by the maximum relevance minimum redundancy method. Two feature lists were obtained in which genes were ranked rigorously. The incremental feature selection method was applied to the mRMR feature list to extract the optimal feature subset, which can be used in the support vector machine algorithm to determine the best performance for the detection of cancer subtypes and healthy controls. The ten-fold cross-validation for the constructed optimal classification model yielded an overall accuracy of 0.751. On the other hand, we extracted the top eighteen features (genes), including TTN, RHOH, RPS20, TRBC2, in another feature list, the MaxRel feature list, and performed a detailed analysis of them. The results indicated that these genes could be important biomarkers for discriminating different cancer subtypes and healthy controls.
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Affiliation(s)
- Yu-Hang Zhang
- Department of General Surgery, Shanghai Jiao Tong University Affiliated Sixth People's Hospital, Shanghai 200233, People's Republic of China.,Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 200031, People's Republic of China
| | - Tao Huang
- Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 200031, People's Republic of China
| | - Lei Chen
- College of Information Engineering, Shanghai Maritime University, Shanghai 201306, People's Republic of China
| | - YaoChen Xu
- Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, People's Republic of China
| | - Yu Hu
- Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 200031, People's Republic of China
| | - Lan-Dian Hu
- Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 200031, People's Republic of China
| | - Yudong Cai
- School of Life Sciences, Shanghai University, Shanghai 200444, People's Republic of China
| | - Xiangyin Kong
- Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, University of Chinese Academy of Sciences, Shanghai 200031, People's Republic of China
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25
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Two chaperones locked in an embrace: structure and function of the ribosome-associated complex RAC. Nat Struct Mol Biol 2017; 24:611-619. [PMID: 28771464 DOI: 10.1038/nsmb.3435] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 06/14/2017] [Indexed: 12/26/2022]
Abstract
Chaperones, which assist protein folding are essential components of every living cell. The yeast ribosome-associated complex (RAC) is a chaperone that is highly conserved in eukaryotic cells. The RAC consists of the J protein Zuo1 and the unconventional Hsp70 homolog Ssz1. The RAC heterodimer stimulates the ATPase activity of the ribosome-bound Hsp70 homolog Ssb, which interacts with nascent polypeptide chains to facilitate de novo protein folding. In addition, the RAC-Ssb system is required to maintain the fidelity of protein translation. Recent work reveals important details of the unique structures of RAC and Ssb and identifies how the chaperones interact with the ribosome. The new findings start to uncover how the exceptional chaperone triad cooperates in protein folding and maintenance of translational fidelity and its connection to extraribosomal functions.
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26
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Ponce-Rojas JC, Avendaño-Monsalve MC, Yañez-Falcón AR, Jaimes-Miranda F, Garay E, Torres-Quiroz F, DeLuna A, Funes S. αβ'-NAC cooperates with Sam37 to mediate early stages of mitochondrial protein import. FEBS J 2017; 284:814-830. [PMID: 28109174 DOI: 10.1111/febs.14024] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2016] [Revised: 12/20/2016] [Accepted: 01/18/2017] [Indexed: 11/30/2022]
Abstract
The mitochondrial proteome is mostly composed of nuclear-encoded proteins. Such polypeptides are synthesized with signals that guide their intracellular transport to the surface of the organelle and later within the different mitochondrial subcompartments until they reach their functional destination. It has been suggested that the nascent-polypeptide associated complex (NAC) - a cytosolic chaperone that recognizes nascent chains on translationally active ribosomes - has a role in the import of nuclear-encoded mitochondrial proteins. However, the molecular mechanisms that regulate the NAC-mediated cotranslational import are still not clear. Here, we show that a particular NAC heterodimer formed by subunits α and β' in Saccharomyces cerevisiae is specifically involved in the process of mitochondrial import and functionally cooperates with Sam37, an outer membrane protein subunit of the sorting and assembly machinery complex. Mutants in both components display growth defects, incorrectly accumulate precursor forms of mitochondrial proteins in the cytosol, and have an altered mitochondrial protein content. We propose that αβ'-NAC and Sam37 are members of the system that recognizes mitochondrial proteins at early stages of their synthesis, escorting them to the import machinery of mitochondria.
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Affiliation(s)
- José Carlos Ponce-Rojas
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico
| | - Maria Clara Avendaño-Monsalve
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico
| | - Armando Roberto Yañez-Falcón
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico
| | - Fabiola Jaimes-Miranda
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico
| | - Erika Garay
- Unidad de Genómica Avanzada (Langebio), Centro de Investigación y de Estudios Avanzados del IPN, Irapuato, Mexico
| | - Francisco Torres-Quiroz
- Departamento de Bioquímica y Biología Estructural, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico
| | - Alexander DeLuna
- Unidad de Genómica Avanzada (Langebio), Centro de Investigación y de Estudios Avanzados del IPN, Irapuato, Mexico
| | - Soledad Funes
- Departamento de Genética Molecular, Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, Mexico
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27
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Multivalent contacts of the Hsp70 Ssb contribute to its architecture on ribosomes and nascent chain interaction. Nat Commun 2016; 7:13695. [PMID: 27917864 PMCID: PMC5150220 DOI: 10.1038/ncomms13695] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 10/25/2016] [Indexed: 01/11/2023] Open
Abstract
Hsp70 chaperones assist de novo folding of newly synthesized proteins in all cells. In yeast, the specialized Hsp70 Ssb directly binds to ribosomes. The structural basis and functional mode of recruitment of Ssb to ribosomes is not understood. Here, we present the molecular details underlying ribosome binding of Ssb in Saccharomyces cerevisiae. This interaction is multifaceted, involving the co-chaperone RAC and two specific regions within Ssb characterized by positive charges. The C-terminus of Ssb mediates the key contact and a second attachment point is provided by a KRR-motif in the substrate binding domain. Strikingly, ribosome binding of Ssb is not essential. Autonomous ribosome attachment becomes necessary if RAC is absent, suggesting a dual mode of Ssb recruitment to nascent chains. We propose, that the multilayered ribosomal interaction allows positioning of Ssb in an optimal orientation to the tunnel exit guaranteeing an efficient nascent polypeptide interaction. The correct folding of proteins often requires the intervention molecular chaperones, which can occur co-translationally. Here the authors identify elements of yeast Ssb (Hsp70) that mediate ribosomal binding, and suggest a mechanism that directs efficient interaction of Ssb with the nascent chain.
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28
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Gumiero A, Conz C, Gesé GV, Zhang Y, Weyer FA, Lapouge K, Kappes J, von Plehwe U, Schermann G, Fitzke E, Wölfle T, Fischer T, Rospert S, Sinning I. Interaction of the cotranslational Hsp70 Ssb with ribosomal proteins and rRNA depends on its lid domain. Nat Commun 2016; 7:13563. [PMID: 27882919 PMCID: PMC5123055 DOI: 10.1038/ncomms13563] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2016] [Accepted: 10/13/2016] [Indexed: 12/22/2022] Open
Abstract
Cotranslational chaperones assist in de novo folding of nascent polypeptides in all organisms. In yeast, the heterodimeric ribosome-associated complex (RAC) forms a unique chaperone triad with the Hsp70 homologue Ssb. We report the X-ray structure of full length Ssb in the ATP-bound open conformation at 2.6 Å resolution and identify a positively charged region in the α-helical lid domain (SBDα), which is present in all members of the Ssb-subfamily of Hsp70s. Mutational analysis demonstrates that this region is strictly required for ribosome binding. Crosslinking shows that Ssb binds close to the tunnel exit via contacts with both, ribosomal proteins and rRNA, and that specific contacts can be correlated with switching between the open (ATP-bound) and closed (ADP-bound) conformation. Taken together, our data reveal how Ssb dynamics on the ribosome allows for the efficient interaction with nascent chains upon RAC-mediated activation of ATP hydrolysis. In yeast, the heterodimeric ribosome-associated complex (RAC) acts in concert with the Hsp70 protein Ssb, forming a unique chaperone triad. Here the authors use structural and biochemical approaches to shed light on how translation and folding are coupled in eukaryotes.
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Affiliation(s)
- Andrea Gumiero
- Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany
| | - Charlotte Conz
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, D-79104 Freiburg, Germany.,BIOSS Centre for Biological Signaling Studies, University of Freiburg, D-79104 Freiburg, Germany
| | - Genís Valentín Gesé
- Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany
| | - Ying Zhang
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, D-79104 Freiburg, Germany.,BIOSS Centre for Biological Signaling Studies, University of Freiburg, D-79104 Freiburg, Germany
| | - Felix Alexander Weyer
- Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany
| | - Karine Lapouge
- Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany
| | - Julia Kappes
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, D-79104 Freiburg, Germany
| | - Ulrike von Plehwe
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, D-79104 Freiburg, Germany
| | - Géza Schermann
- Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany
| | - Edith Fitzke
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, D-79104 Freiburg, Germany.,BIOSS Centre for Biological Signaling Studies, University of Freiburg, D-79104 Freiburg, Germany
| | - Tina Wölfle
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, D-79104 Freiburg, Germany.,BIOSS Centre for Biological Signaling Studies, University of Freiburg, D-79104 Freiburg, Germany
| | - Tamás Fischer
- Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany
| | - Sabine Rospert
- Institute of Biochemistry and Molecular Biology, ZBMZ, Faculty of Medicine, University of Freiburg, D-79104 Freiburg, Germany.,BIOSS Centre for Biological Signaling Studies, University of Freiburg, D-79104 Freiburg, Germany
| | - Irmgard Sinning
- Heidelberg University Biochemistry Center (BZH), INF 328, D-69120 Heidelberg, Germany
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29
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Keefer KM, True HL. Prion-Associated Toxicity is Rescued by Elimination of Cotranslational Chaperones. PLoS Genet 2016; 12:e1006431. [PMID: 27828954 PMCID: PMC5102407 DOI: 10.1371/journal.pgen.1006431] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2016] [Accepted: 10/18/2016] [Indexed: 12/30/2022] Open
Abstract
The nascent polypeptide-associated complex (NAC) is a highly conserved but poorly characterized triad of proteins that bind near the ribosome exit tunnel. The NAC is the first cotranslational factor to bind to polypeptides and assist with their proper folding. Surprisingly, we found that deletion of NAC subunits in Saccharomyces cerevisiae rescues toxicity associated with the strong [PSI+] prion. This counterintuitive finding can be explained by changes in chaperone balance and distribution whereby the folding of the prion protein is improved and the prion is rendered nontoxic. In particular, the ribosome-associated Hsp70 Ssb is redistributed away from Sup35 prion aggregates to the nascent chains, leading to an array of aggregation phenotypes that can mimic both overexpression and deletion of Ssb. This toxicity rescue demonstrates that chaperone modification can block key steps of the prion life cycle and has exciting implications for potential treatment of many human protein conformational disorders. Misfolded proteins can be toxic to cells, causing pathologies such as Alzheimer’s disease, Parkinson’s disease, prion diseases, and ALS. One mechanism by which organisms combat protein misfolding involves molecular chaperones, proteins that help other proteins fold correctly. Here, we describe a novel role for a family of chaperones called the nascent polypeptide-associated complex (NAC). The NAC is a group of proteins that exist in all multicellular organisms, yet we do not fully understand its function. Using yeast as a model system, we have found that deletion of NAC subunits can reduce the toxicity associated with misfolded proteins. This work has implications for human protein misfolding diseases, as modulation of the NAC may present a viable therapeutic avenue by which to slow the progression of neurodegeneration and other protein conformational disorders.
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Affiliation(s)
- Kathryn M. Keefer
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Heather L. True
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, Missouri, United States of America
- * E-mail:
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30
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Greber BJ. Mechanistic insight into eukaryotic 60S ribosomal subunit biogenesis by cryo-electron microscopy. RNA (NEW YORK, N.Y.) 2016; 22:1643-1662. [PMID: 27875256 PMCID: PMC5066618 DOI: 10.1261/rna.057927.116] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Eukaryotic ribosomes, the protein-producing factories of the cell, are composed of four ribosomal RNA molecules and roughly 80 proteins. Their biogenesis is a complex process that involves more than 200 biogenesis factors that facilitate the production, modification, and assembly of ribosomal components and the structural transitions along the maturation pathways of the pre-ribosomal particles. Here, I review recent structural and mechanistic insights into the biogenesis of the large ribosomal subunit that were furthered by cryo-electron microscopy of natively purified pre-60S particles and in vitro reconstituted ribosome assembly factor complexes. Combined with biochemical, genetic, and previous structural data, these structures have provided detailed insights into the assembly and maturation of the central protuberance of the 60S subunit, the network of biogenesis factors near the ribosomal tunnel exit, and the functional activation of the large ribosomal subunit during cytoplasmic maturation.
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Affiliation(s)
- Basil J Greber
- California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, California 94720-3220, USA
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31
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Lee K, Sharma R, Shrestha OK, Bingman CA, Craig EA. Dual interaction of the Hsp70 J-protein cochaperone Zuotin with the 40S and 60S ribosomal subunits. Nat Struct Mol Biol 2016; 23:1003-1010. [PMID: 27669034 PMCID: PMC5097012 DOI: 10.1038/nsmb.3299] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2016] [Accepted: 08/31/2016] [Indexed: 12/30/2022]
Abstract
Ribosome-associated J protein-Hsp70 chaperones promote nascent polypeptide folding and normal translational fidelity. Though known to span the ribosome subunits, understanding of J protein Zuo1 function is limited. New structural and crosslinking data allow more precise positioning of Saccharomyces cerevisiae Zuo1 near the 60S polypeptide exit site, pointing to interactions with ribosomal protein eL31 and 25S rRNA helix 24. The junction between the 60S-interacting and subunit-spanning helices is a hinge, positioning Zuo1 on the 40S, yet accommodating subunit rotation. Interaction between C-terminus of Zuo1 and 40S occurs via 18S rRNA expansion segment 12 (ES12) of helix 44, which originates at the decoding site. Deletions in either ES12 or C-terminus of Zuo1 alter stop codon readthrough and −1 frameshifting. Our study offers insight into how this cotranslational chaperone system may monitor decoding site activity and nascent polypeptide transit, thereby coordinating protein translation and folding.
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Affiliation(s)
- Kanghyun Lee
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Ruchika Sharma
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Om Kumar Shrestha
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Craig A Bingman
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
| | - Elizabeth A Craig
- Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin, USA
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32
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Kim SJ, Strich R. Rpl22 is required for IME1 mRNA translation and meiotic induction in S. cerevisiae. Cell Div 2016; 11:10. [PMID: 27478489 PMCID: PMC4966820 DOI: 10.1186/s13008-016-0024-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 07/08/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The transition from mitotic cell division to meiotic development in S. cerevisiae requires induction of a transient transcription program that is initiated by Ime1-dependent destruction of the repressor Ume6. Although IME1 mRNA is observed in vegetative cultures, Ime1 protein is not suggesting the presence of a regulatory system restricting translation to meiotic cells. RESULTS This study demonstrates that IME1 mRNA translation requires Rpl22A and Rpl22B, eukaryotic-specific ribosomal protein paralogs of the 60S large subunit. In the absence of Rpl22 function, IME1 mRNA synthesis is normal in cultures induced to enter meiosis. However, Ime1 protein production is reduced and the Ume6 repressor is not destroyed in rpl22 mutant cells preventing early meiotic gene induction resulting in a pre-meiosis I arrest. This role for Rpl22 is not a general consequence of mutating non-essential large ribosomal proteins as strains lacking Rpl29 or Rpl39 execute meiosis with nearly wild-type efficiencies. Several results indicate that Rpl22 functions by enhancing IME1 mRNA translation. First, the Ime1 protein synthesized in rpl22 mutant cells demonstrates the same turnover rate as in wild-type cultures. In addition, IME1 transcript is found in polysome fractions isolated from rpl22 mutant cells indicating that mRNA nuclear export and ribosome association occurs. Finally, deleting the unusually long 5'UTR restores Ime1 levels and early meiotic gene transcription in rpl22 mutants suggesting that Rpl22 enhances translation through this element. Polysome profiles revealed that under conditions of high translational output, Rpl22 maintains high free 60S subunit levels thus preventing halfmer formation, a translation species indicative of mRNAs bound by an unpaired 40S subunit. In addition to meiosis, Rpl22 is also required for invasive and pseudohyphal growth. CONCLUSIONS These findings indicate that Rpl22A and Rpl22B are required to selectively translate IME1 mRNA that is required for meiotic induction and subsequent gametogenesis. In addition, our results imply a more general role for Rpl22 in cell fate switches responding to environmental nitrogen signals.
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Affiliation(s)
- Stephen J Kim
- Department of Molecular Biology, Rowan University School of Osteopathic Medicine, Two Medical Center Dr., Stratford, NJ 08055 USA
| | - Randy Strich
- Department of Molecular Biology, Rowan University School of Osteopathic Medicine, Two Medical Center Dr., Stratford, NJ 08055 USA
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33
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Nyathi Y, Pool MR. Analysis of the interplay of protein biogenesis factors at the ribosome exit site reveals new role for NAC. J Cell Biol 2016. [PMID: 26195668 PMCID: PMC4508901 DOI: 10.1083/jcb.201410086] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The protein biogenesis factor NAC regulates the access of the enzyme MetAP and the signal recognition particle (SRP) to the ribosome, functions in SRP-dependent targeting, and can act to protect substrates from aggregation before translocation The ribosome exit site is a focal point for the interaction of protein-biogenesis factors that guide the fate of nascent polypeptides. These factors include chaperones such as NAC, N-terminal-modifying enzymes like Methionine aminopeptidase (MetAP), and the signal recognition particle (SRP), which targets secretory and membrane proteins to the ER. These factors potentially compete with one another in the short time-window when the nascent chain first emerges at the exit site, suggesting a need for regulation. Here, we show that MetAP contacts the ribosome at the universal adaptor site where it is adjacent to the α subunit of NAC. SRP is also known to contact the ribosome at this site. In the absence of NAC, MetAP and SRP antagonize each other, indicating a novel role for NAC in regulating the access of MetAP and SRP to the ribosome. NAC also functions in SRP-dependent targeting and helps to protect substrates from aggregation before translocation.
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Affiliation(s)
- Yvonne Nyathi
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, England, UK
| | - Martin R Pool
- Faculty of Life Sciences, University of Manchester, Manchester M13 9PT, England, UK
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34
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Ribosomal Protein Rps26 Influences 80S Ribosome Assembly in Saccharomyces cerevisiae. mSphere 2016; 1:mSphere00109-15. [PMID: 27303706 PMCID: PMC4863615 DOI: 10.1128/msphere.00109-15] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2015] [Accepted: 02/04/2016] [Indexed: 11/20/2022] Open
Abstract
Rps26 is an essential protein of the eukaryotic small ribosomal subunit. Previous experiments demonstrated an interaction between the eukaryote-specific Y62–K70 segment of Rps26 and the 5′ untranslated region of mRNA. The data suggested a specific role of the Y62–K70 motif during translation initiation. Here, we report that single-site substitutions within the Y62–K70 peptide did not affect the growth of engineered yeast strains, arguing against its having a critical role during translation initiation via specific interactions with the 5′ untranslated region of mRNA molecules. Only the simultaneous replacement of five conserved residues within the Y62–K70 fragment or the replacement of the yeast protein with the human homolog resulted in growth defects and caused significant changes in polysome profiles. The results expand our knowledge of ribosomal protein function and suggest a role of Rps26 during ribosome assembly in yeast. The eukaryotic ribosome consists of a small (40S) and a large (60S) subunit. Rps26 is one of the essential ribosomal proteins of the 40S subunit and is encoded by two almost identical genes, RPS26a and RPS26b. Previous studies demonstrated that Rps26 interacts with the 5′ untranslated region of mRNA via the eukaryote-specific 62-YXXPKXYXK-70 (Y62–K70) motif. Those observations suggested that this peptide within Rps26 might play an important and specific role during translation initiation. By using alanine-scanning mutagenesis and engineered strains of the yeast Saccharomyces cerevisiae, we found that single amino acid substitutions within the Y62–K70 motif of Rps26 did not affect the in vivo function of the protein. In contrast, complete deletion of the Y62–K70 segment was lethal. The simultaneous replacement of five conserved residues within the Y62–K70 segment by alanines resulted in growth defects under stress conditions and produced distinct changes in polysome profiles that were indicative of the accumulation of free 60S subunits. Human Rps26 (Rps26-Hs), which displays significant homology with yeast Rps26, supported the growth of an S. cerevisiae Δrps26a Δrps26b strain. However, the Δrps26a Δrps26b double deletion strain expressing Rps26-Hs displayed substantial growth defects and an altered ratio of 40S/60S ribosomal subunits. The combined data strongly suggest that the eukaryote-specific motif within Rps26 does not play a specific role in translation initiation. Rather, the data indicate that Rps26 as a whole is necessary for proper assembly of the 40S subunit and the 80S ribosome in yeast. IMPORTANCE Rps26 is an essential protein of the eukaryotic small ribosomal subunit. Previous experiments demonstrated an interaction between the eukaryote-specific Y62–K70 segment of Rps26 and the 5′ untranslated region of mRNA. The data suggested a specific role of the Y62–K70 motif during translation initiation. Here, we report that single-site substitutions within the Y62–K70 peptide did not affect the growth of engineered yeast strains, arguing against its having a critical role during translation initiation via specific interactions with the 5′ untranslated region of mRNA molecules. Only the simultaneous replacement of five conserved residues within the Y62–K70 fragment or the replacement of the yeast protein with the human homolog resulted in growth defects and caused significant changes in polysome profiles. The results expand our knowledge of ribosomal protein function and suggest a role of Rps26 during ribosome assembly in yeast.
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Belyy A, Tabakova I, Lang AE, Jank T, Belyi Y, Aktories K. Roles of Asp179 and Glu270 in ADP-Ribosylation of Actin by Clostridium perfringens Iota Toxin. PLoS One 2015; 10:e0145708. [PMID: 26713879 PMCID: PMC4699905 DOI: 10.1371/journal.pone.0145708] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2015] [Accepted: 12/08/2015] [Indexed: 12/19/2022] Open
Abstract
Clostridium perfringens iota toxin is a binary toxin composed of the enzymatically active component Ia and receptor binding component Ib. Ia is an ADP-ribosyltransferase, which modifies Arg177 of actin. The previously determined crystal structure of the actin-Ia complex suggested involvement of Asp179 of actin in the ADP-ribosylation reaction. To gain more insights into the structural requirements of actin to serve as a substrate for toxin-catalyzed ADP-ribosylation, we engineered Saccharomyces cerevisiae strains, in which wild type actin was replaced by actin variants with substitutions in residues located on the Ia-actin interface. Expression of the actin mutant Arg177Lys resulted in complete resistance towards Ia. Actin mutation of Asp179 did not change Ia-induced ADP-ribosylation and growth inhibition of S. cerevisiae. By contrast, substitution of Glu270 of actin inhibited the toxic action of Ia and the ADP-ribosylation of actin. In vitro transcribed/translated human β-actin confirmed the crucial role of Glu270 in ADP-ribosylation of actin by Ia.
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Affiliation(s)
- Alexander Belyy
- Gamaleya Research Institute, Moscow, Russia
- Faculty of Biology, Lomonosov Moscow State University, Moscow, Russia
| | | | - Alexander E. Lang
- Institute for Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, Freiburg, Germany
| | - Thomas Jank
- Institute for Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, Freiburg, Germany
| | - Yury Belyi
- Gamaleya Research Institute, Moscow, Russia
- Freiburg Institute for Advanced Studies (FRIAS), University of Freiburg, Freiburg, Germany
| | - Klaus Aktories
- Institute for Experimental and Clinical Pharmacology and Toxicology, University of Freiburg, Freiburg, Germany
- Freiburg Institute for Advanced Studies (FRIAS), University of Freiburg, Freiburg, Germany
- Centre for Biological Signalling Studies (BIOSS), University of Freiburg, Freiburg, Germany
- * E-mail:
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Breiman A, Fieulaine S, Meinnel T, Giglione C. The intriguing realm of protein biogenesis: Facing the green co-translational protein maturation networks. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2015; 1864:531-50. [PMID: 26555180 DOI: 10.1016/j.bbapap.2015.11.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 11/05/2015] [Indexed: 01/13/2023]
Abstract
The ribosome is the cell's protein-making factory, a huge protein-RNA complex, that is essential to life. Determining the high-resolution structures of the stable "core" of this factory was among the major breakthroughs of the past decades, and was awarded the Nobel Prize in 2009. Now that the mysteries of the ribosome appear to be more traceable, detailed understanding of the mechanisms that regulate protein synthesis includes not only the well-known steps of initiation, elongation, and termination but also the less comprehended features of the co-translational events associated with the maturation of the nascent chains. The ribosome is a platform for co-translational events affecting the nascent polypeptide, including protein modifications, folding, targeting to various cellular compartments for integration into membrane or translocation, and proteolysis. These events are orchestrated by ribosome-associated protein biogenesis factors (RPBs), a group of a dozen or more factors that act as the "welcoming committee" for the nascent chain as it emerges from the ribosome. In plants these factors have evolved to fit the specificity of different cellular compartments: cytoplasm, mitochondria and chloroplast. This review focuses on the current state of knowledge of these factors and their interaction around the exit tunnel of dedicated ribosomes. Particular attention has been accorded to the plant system, highlighting the similarities and differences with other organisms.
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Affiliation(s)
- Adina Breiman
- Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Univ. Paris-Saclay 91198 Gif-sur-Yvette cedex, France; Department of Molecular Biology and Ecology of Plants, Tel Aviv University, Tel Aviv 69978, Israel
| | - Sonia Fieulaine
- Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Univ. Paris-Saclay 91198 Gif-sur-Yvette cedex, France
| | - Thierry Meinnel
- Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Univ. Paris-Saclay 91198 Gif-sur-Yvette cedex, France
| | - Carmela Giglione
- Institute of Integrative Biology of the Cell (I2BC), CEA, CNRS, Univ. Paris-Sud, Univ. Paris-Saclay 91198 Gif-sur-Yvette cedex, France.
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Wright MA, Aprile FA, Arosio P, Vendruscolo M, Dobson CM, Knowles TPJ. Biophysical approaches for the study of interactions between molecular chaperones and protein aggregates. Chem Commun (Camb) 2015; 51:14425-34. [PMID: 26328629 PMCID: PMC8597951 DOI: 10.1039/c5cc03689e] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2015] [Accepted: 08/07/2015] [Indexed: 12/25/2022]
Abstract
Molecular chaperones are key components of the arsenal of cellular defence mechanisms active against protein aggregation. In addition to their established role in assisting protein folding, increasing evidence indicates that molecular chaperones are able to protect against a range of potentially damaging aspects of protein behaviour, including misfolding and aggregation events that can result in the generation of aberrant protein assemblies whose formation is implicated in the onset and progression of neurodegenerative disorders such as Alzheimer's and Parkinson's diseases. The interactions between molecular chaperones and different amyloidogenic protein species are difficult to study owing to the inherent heterogeneity of the aggregation process as well as the dynamic nature of molecular chaperones under physiological conditions. As a consequence, understanding the detailed microscopic mechanisms underlying the nature and means of inhibition of aggregate formation remains challenging yet is a key objective for protein biophysics. In this review, we discuss recent results from biophysical studies on the interactions between molecular chaperones and protein aggregates. In particular, we focus on the insights gained from current experimental techniques into the dynamics of the oligomerisation process of molecular chaperones, and highlight the opportunities that future biophysical approaches have in advancing our understanding of the great variety of biological functions of this important class of proteins.
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Affiliation(s)
- Maya A. Wright
- Department of Chemistry, University of CambridgeLensfield RoadCambridge CB2 1EWUK+44 (0)1223 336300
| | - Francesco A. Aprile
- Department of Chemistry, University of CambridgeLensfield RoadCambridge CB2 1EWUK+44 (0)1223 336300
| | - Paolo Arosio
- Department of Chemistry, University of CambridgeLensfield RoadCambridge CB2 1EWUK+44 (0)1223 336300
| | - Michele Vendruscolo
- Department of Chemistry, University of CambridgeLensfield RoadCambridge CB2 1EWUK+44 (0)1223 336300
| | - Christopher M. Dobson
- Department of Chemistry, University of CambridgeLensfield RoadCambridge CB2 1EWUK+44 (0)1223 336300
| | - Tuomas P. J. Knowles
- Department of Chemistry, University of CambridgeLensfield RoadCambridge CB2 1EWUK+44 (0)1223 336300
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Kim DH, Lee JE, Xu ZY, Geem KR, Kwon Y, Park JW, Hwang I. Cytosolic targeting factor AKR2A captures chloroplast outer membrane-localized client proteins at the ribosome during translation. Nat Commun 2015; 6:6843. [PMID: 25880450 DOI: 10.1038/ncomms7843] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2014] [Accepted: 03/04/2015] [Indexed: 01/30/2023] Open
Abstract
In eukaryotic cells, organellar proteome biogenesis is pivotal for cellular function. Chloroplasts contain a complex proteome, the biogenesis of which includes post-translational import of nuclear-encoded proteins. However, the mechanisms determining when and how nascent chloroplast-targeted proteins are sorted in the cytosol are unknown. Here, we establish the timing and mode of interaction between ankyrin repeat-containing protein 2 (AKR2A), the cytosolic targeting factor of chloroplast outer membrane (COM) proteins, and its interacting partners during translation at the single-molecule level. The targeting signal of a nascent AKR2A client protein residing in the ribosomal exit tunnel induces AKR2A binding to ribosomal RPL23A. Subsequently, RPL23A-bound AKR2A binds to the targeting signal when it becomes exposed from ribosomes. Failure of AKR2A binding to RPL23A in planta severely disrupts protein targeting to the COM; thus, AKR2A-mediated targeting of COM proteins is coupled to their translation, which in turn is crucial for biogenesis of the entire chloroplast proteome.
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Affiliation(s)
- Dae Heon Kim
- Department of Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - Jae-Eun Lee
- Department of Chemistry, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - Zheng-Yi Xu
- Department of Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - Kyoung Rok Geem
- Department of Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - Yun Kwon
- Department of Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - Joon Won Park
- Department of Chemistry, Pohang University of Science and Technology, Pohang 790-784, Korea
| | - Inhwan Hwang
- Department of Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Korea.,Division of Integrative Biosciences and Biotechnology, Pohang University of Science and Technology, Pohang 790-784, Korea
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Kaschner LA, Sharma R, Shrestha OK, Meyer AE, Craig EA. A conserved domain important for association of eukaryotic J-protein co-chaperones Jjj1 and Zuo1 with the ribosome. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2015; 1853:1035-45. [PMID: 25639645 DOI: 10.1016/j.bbamcr.2015.01.014] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/29/2014] [Revised: 01/20/2015] [Accepted: 01/22/2015] [Indexed: 11/28/2022]
Abstract
J-proteins, obligate co-chaperones, provide specialization for Hsp70 function in a variety of cellular processes. Two of the 13 J-proteins of the yeast cytosol/nucleus, Zuo1 and Jjj1, are associated with 60S ribosomal subunits. Abundant Zuo1 facilitates folding of nascent polypeptides; Jjj1, of much lower abundance, functions in ribosome biogenesis. However, overexpression of Jjj1 substantially rescues growth defects of cells lacking Zuo1. We analyzed a region held in common by Zuo1 and Jjj1, outside the signature J-domain found in all J-proteins. This shared "zuotin homology domain" (ZHD) is important for ribosome association of both proteins. An N-terminal segment of Jjj1, containing the J-domain and ZHD, is ribosome-associated and, like full-length Jjj1, is competent to rescue both the cold- and cation-sensitivity of ∆zuo1. However, this fragment, when expressed at normal levels, cannot rescue the cytosolic ribosome biogenesis defect of ∆jjj1. Our results are consistent with a model in which the primary functions of Zuo1 and Jjj1 occur in the cytosol. In addition, our data suggest that Zuo1 and Jjj1 bind overlapping sites on ribosomes due to an interaction via their common ZHDs, but Jjj1 binds primarily to pre-60S particles and Zuo1 to mature subunits. We hypothesize that ZUO1 and JJJ1, which are conserved throughout eukaryotes, arose from an ancient duplication of a progenitor J-protein gene that encoded the ZHD ribosome-binding region; subsequently, specialized roles and additional ribosome interaction sites evolved.
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Affiliation(s)
- Lindsey A Kaschner
- Graduate Program in Cellular and Molecular Biology, University of Wisconsin-Madison, USA; Department of Biochemistry, University of Wisconsin-Madison, USA
| | - Ruchika Sharma
- Department of Biochemistry, University of Wisconsin-Madison, USA
| | | | - Alison E Meyer
- Department of Biochemistry, University of Wisconsin-Madison, USA
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Structural basis for interaction of a cotranslational chaperone with the eukaryotic ribosome. Nat Struct Mol Biol 2014; 21:1042-6. [PMID: 25362488 DOI: 10.1038/nsmb.2908] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2014] [Accepted: 09/30/2014] [Indexed: 11/08/2022]
Abstract
Cotranslational chaperones, ubiquitous in all living organisms, protect nascent polypeptides from aggregation and facilitate their de novo folding. Importantly, emerging data have also suggested that ribosome-associated cotranslational chaperones have active regulatory roles in modulating protein translation. By characterizing the structure of a type of eukaryotic cotranslational chaperone, the ribosome-associated complex (RAC) from Saccharomyces cerevisiae, we show that RAC cross-links two ribosomal subunits, through a single long α-helix, to limit the predominant intersubunit rotation required for peptide elongation. We further demonstrate that any changes in the continuity, length or rigidity of this middle α-helix impair RAC function in vivo. Our results suggest a new mechanism in which RAC directly regulates protein translation by mechanically coupling cotranslational folding with the peptide-elongation cycle, and they lay the foundation for further exploration of regulatory roles of RAC in translation control.
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Maruyama Y, Miyazaki T, Ikeda K, Okumura T, Sato W, Horie-Inoue K, Okamoto K, Takeda S, Inoue S. Short hairpin RNA library-based functional screening identified ribosomal protein L31 that modulates prostate cancer cell growth via p53 pathway. PLoS One 2014; 9:e108743. [PMID: 25285958 PMCID: PMC4186824 DOI: 10.1371/journal.pone.0108743] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Accepted: 08/25/2014] [Indexed: 11/22/2022] Open
Abstract
Androgen receptor is a primary transcription factor involved in the proliferation of prostate cancer cells. Thus, hormone therapy using antiandrogens, such as bicalutamide, is a first-line treatment for the disease. Although hormone therapy initially reduces the tumor burden, many patients eventually relapse, developing tumors with acquired endocrine resistance. Elucidation of the molecular mechanisms underlying endocrine resistance is therefore a fundamental issue for the understanding and development of alternative therapeutics for advanced prostate cancer. In the present study, we performed short hairpin RNA (shRNA)-mediated functional screening to identify genes involved in bicalutamide-mediated effects on LNCaP prostate cancer cells. Among such candidate genes selected by screening using volcano plot analysis, ribosomal protein L31 (RPL31) was found to be essential for cell proliferation and cell-cycle progression in bicalutamide-resistant LNCaP (BicR) cells, based on small interfering RNA (siRNA)-mediated knockdown experiments. Of note, RPL31 mRNA is more abundantly expressed in BicR cells than in parental LNCaP cells, and clinical data from ONCOMINE and The Cancer Genome Altas showed that RPL31 is overexpressed in prostate carcinomas compared with benign prostate tissues. Intriguingly, protein levels of the tumor suppressor p53 and its targets, p21 and MDM2, were increased in LNCaP and BicR cells treated with RPL31 siRNA. We observed decreased degradation of p53 protein after RPL31 knockdown. Moreover, the suppression of growth and cell cycle upon RPL31 knockdown was partially recovered with p53 siRNA treatment. These results suggest that RPL31 is involved in bicalutamide-resistant growth of prostate cancer cells. The shRNA-mediated functional screen in this study provides new insight into the molecular mechanisms and therapeutic targets of advanced prostate cancer.
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Affiliation(s)
- Yojiro Maruyama
- Division of Gene Regulation and Signal Transduction, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan
- Department of Obstetrics and Gynecology, Juntendo University School of Medicine, Tokyo, Japan
| | - Toshiaki Miyazaki
- Division of Gene Regulation and Signal Transduction, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan
| | - Kazuhiro Ikeda
- Division of Gene Regulation and Signal Transduction, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan
| | - Toshiyuki Okumura
- Division of Gene Regulation and Signal Transduction, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan
| | - Wataru Sato
- Division of Gene Regulation and Signal Transduction, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan
| | - Kuniko Horie-Inoue
- Division of Gene Regulation and Signal Transduction, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan
| | - Koji Okamoto
- Division of Cancer Differentiation, National Cancer Center Research Institute, Tokyo, Japan
| | - Satoru Takeda
- Department of Obstetrics and Gynecology, Juntendo University School of Medicine, Tokyo, Japan
| | - Satoshi Inoue
- Division of Gene Regulation and Signal Transduction, Research Center for Genomic Medicine, Saitama Medical University, Saitama, Japan
- Departments of Geriatric Medicine and Anti-Aging Medicine, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan
- * E-mail:
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Release factor eRF3 mediates premature translation termination on polylysine-stalled ribosomes in Saccharomyces cerevisiae. Mol Cell Biol 2014; 34:4062-76. [PMID: 25154418 DOI: 10.1128/mcb.00799-14] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Ribosome stalling is an important incident enabling the cellular quality control machinery to detect aberrant mRNA. Saccharomyces cerevisiae Hbs1-Dom34 and Ski7 are homologs of the canonical release factor eRF3-eRF1, which recognize stalled ribosomes, promote ribosome release, and induce the decay of aberrant mRNA. Polyadenylated nonstop mRNA encodes aberrant proteins containing C-terminal polylysine segments which cause ribosome stalling due to electrostatic interaction with the ribosomal exit tunnel. Here we describe a novel mechanism, termed premature translation termination, which releases C-terminally truncated translation products from ribosomes stalled on polylysine segments. Premature termination during polylysine synthesis was abolished when ribosome stalling was prevented due to the absence of the ribosomal protein Asc1. In contrast, premature termination was enhanced, when the general rate of translation elongation was lowered. The unconventional termination event was independent of Hbs1-Dom34 and Ski7, but it was dependent on eRF3. Moreover, premature termination during polylysine synthesis was strongly increased in the absence of the ribosome-bound chaperones ribosome-associated complex (RAC) and Ssb (Ssb1 and Ssb2). On the basis of the data, we suggest a model in which eRF3-eRF1 can catalyze the release of nascent polypeptides even though the ribosomal A-site contains a sense codon when the rate of translation is abnormally low.
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Chen DH, Huang Y, Liu C, Ruan Y, Shen WH. Functional conservation and divergence of J-domain-containing ZUO1/ZRF orthologs throughout evolution. PLANTA 2014; 239:1159-1173. [PMID: 24659052 DOI: 10.1007/s00425-014-2058-6] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Accepted: 03/05/2014] [Indexed: 06/03/2023]
Abstract
Heat shock protein 40s (Hsp40s), also known as J-proteins, are conserved in prokaryotes and eukaryotes. The Zuotin/Zuotin-related factor (ZUO1/ZRF) family belongs to a novel Hsp40 clade exclusively found in eukaryotes. Zuotin/Zuotin-related factor proteins are characterized by a large N terminal ZUO1 domain originally identified in the yeast ZUO1 protein. The ZUO1 domain is characterized by a highly conserved J-domain, together with an atypical UBD domain first identified in the human ZRF1 protein. Furthermore, ZUO1/ZRF protein families in animals and plants harbor a pair of C terminal SANT domains, suggesting the divergence of their functions with those in fungi. Zuotin/Zuotin-related factor proteins retain the ancestral function as an Hsp70co-chaperone implicated in protein folding and renaturation after stress; these proteins also perform diverse neofunctions in the cytoplasm and transcriptional and/or epigenetic regulatory functions in the nucleus. Therefore, these proteins are involved in translational fidelity control, ribosomal biogenesis, asymmetric cell division, cell cycle, apoptosis, differentiation, and tumorigenesis. The results of sequence and domain organization analysis of proteins from diverse organisms provided valuable insights into the evolutionary conservation and diversity of ZUO1/ZRF protein family. Further, phylogenetic analysis provides a platform for future functional investigation on the ZUO1/ZRF protein family, particularly in higher plants.
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Suzuki K, Nakamura S, Morimoto M, Fujii K, Noda NN, Inagaki F, Ohsumi Y. Proteomic profiling of autophagosome cargo in Saccharomyces cerevisiae. PLoS One 2014; 9:e91651. [PMID: 24626240 PMCID: PMC3953483 DOI: 10.1371/journal.pone.0091651] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 02/12/2014] [Indexed: 11/18/2022] Open
Abstract
Macroautophagy (autophagy) is a bulk protein-degradation system ubiquitously conserved in eukaryotic cells. During autophagy, cytoplasmic components are enclosed in a membrane compartment, called an autophagosome. The autophagosome fuses with the vacuole/lysosome and is degraded together with its cargo. Because autophagy is important for the maintenance of cellular homeostasis by degrading unwanted proteins and organelles, identification of autophagosome cargo proteins (i.e., the targets of autophagy) will aid in understanding the physiological roles of autophagy. In this study, we developed a method for monitoring intact autophagosomes ex vivo by detecting the fluorescence of GFP-fused aminopeptidase I, the best-characterized selective cargo of autophagosomes in Saccharomyces cerevisiae. This method facilitated optimization of a biochemical procedure to fractionate autophagosomes. A combination of LC-MS/MS with subsequent statistical analyses revealed a list of autophagosome cargo proteins; some of these are selectively enclosed in autophagosomes and delivered to the vacuole in an Atg11-independent manner. The methods we describe will be useful for analyzing the mechanisms and physiological significance of Atg11-independent selective autophagy.
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Affiliation(s)
- Kuninori Suzuki
- Bioimaging Center, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba, Japan
- * E-mail:
| | - Shingo Nakamura
- Department of Structural Biology, Faculty of Advanced Life Science, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Mayumi Morimoto
- Frontier Research Center, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan
| | - Kiyonaga Fujii
- Department of Structural Biology, Faculty of Advanced Life Science, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Nobuo N. Noda
- Laboratory of Molecular Structure, Institute of Microbial Chemistry (BIKAKEN), Tokyo, Japan
| | - Fuyuhiko Inagaki
- Department of Structural Biology, Faculty of Advanced Life Science, Hokkaido University, Sapporo, Hokkaido, Japan
| | - Yoshinori Ohsumi
- Frontier Research Center, Tokyo Institute of Technology, Yokohama, Kanagawa, Japan
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Abstract
Each peptide bond of a protein is generated at the peptidyl transferase center (PTC) of the ribosome and then moves through the exit tunnel, which accommodates ever-changing segments of ≈ 40 amino acids of newly translated polypeptide. A class of proteins, called ribosome arrest peptides, contains specific sequences of amino acids (arrest sequences) that interact with distinct components of the PTC-exit tunnel region of the ribosome and arrest their own translation continuation, often in a manner regulated by environmental cues. Thus, the ribosome that has translated an arrest sequence is inactivated for peptidyl transfer, translocation, or termination. The stalled ribosome then changes the configuration or localization of mRNA, resulting in specific biological outputs, including regulation of the target gene expression and downstream events of mRNA/polypeptide maturation or localization. Living organisms thus seem to have integrated potentially harmful arrest sequences into elaborate regulatory mechanisms to express genetic information in productive directions.
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Affiliation(s)
- Koreaki Ito
- Faculty of Life Sciences, Kyoto Sangyo University, Motoyama, Kamigamo, Kita-Ku, Kyoto 603-8555, Japan.
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Kim YE, Hipp MS, Bracher A, Hayer-Hartl M, Hartl FU. Molecular chaperone functions in protein folding and proteostasis. Annu Rev Biochem 2013; 82:323-55. [PMID: 23746257 DOI: 10.1146/annurev-biochem-060208-092442] [Citation(s) in RCA: 999] [Impact Index Per Article: 90.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The biological functions of proteins are governed by their three-dimensional fold. Protein folding, maintenance of proteome integrity, and protein homeostasis (proteostasis) critically depend on a complex network of molecular chaperones. Disruption of proteostasis is implicated in aging and the pathogenesis of numerous degenerative diseases. In the cytosol, different classes of molecular chaperones cooperate in evolutionarily conserved folding pathways. Nascent polypeptides interact cotranslationally with a first set of chaperones, including trigger factor and the Hsp70 system, which prevent premature (mis)folding. Folding occurs upon controlled release of newly synthesized proteins from these factors or after transfer to downstream chaperones such as the chaperonins. Chaperonins are large, cylindrical complexes that provide a central compartment for a single protein chain to fold unimpaired by aggregation. This review focuses on recent advances in understanding the mechanisms of chaperone action in promoting and regulating protein folding and on the pathological consequences of protein misfolding and aggregation.
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Affiliation(s)
- Yujin E Kim
- Department of Cellular Biochemistry, Max Planck Institute of Biochemistry, 82152 Martinsried, Germany
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Woolford JL, Baserga SJ. Ribosome biogenesis in the yeast Saccharomyces cerevisiae. Genetics 2013; 195:643-81. [PMID: 24190922 PMCID: PMC3813855 DOI: 10.1534/genetics.113.153197] [Citation(s) in RCA: 548] [Impact Index Per Article: 49.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Accepted: 08/26/2013] [Indexed: 01/09/2023] Open
Abstract
Ribosomes are highly conserved ribonucleoprotein nanomachines that translate information in the genome to create the proteome in all cells. In yeast these complex particles contain four RNAs (>5400 nucleotides) and 79 different proteins. During the past 25 years, studies in yeast have led the way to understanding how these molecules are assembled into ribosomes in vivo. Assembly begins with transcription of ribosomal RNA in the nucleolus, where the RNA then undergoes complex pathways of folding, coupled with nucleotide modification, removal of spacer sequences, and binding to ribosomal proteins. More than 200 assembly factors and 76 small nucleolar RNAs transiently associate with assembling ribosomes, to enable their accurate and efficient construction. Following export of preribosomes from the nucleus to the cytoplasm, they undergo final stages of maturation before entering the pool of functioning ribosomes. Elaborate mechanisms exist to monitor the formation of correct structural and functional neighborhoods within ribosomes and to destroy preribosomes that fail to assemble properly. Studies of yeast ribosome biogenesis provide useful models for ribosomopathies, diseases in humans that result from failure to properly assemble ribosomes.
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Affiliation(s)
- John L. Woolford
- Department of Biological Sciences, Center for Nucleic Acids Science and Technology, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
| | - Susan J. Baserga
- Molecular Biophysics and Biochemistry, Genetics and Therapeutic Radiology, Yale University, New Haven, Connecticut 06520-8024
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Zhang Y, Wölfle T, Rospert S. Interaction of nascent chains with the ribosomal tunnel proteins Rpl4, Rpl17, and Rpl39 of Saccharomyces cerevisiae. J Biol Chem 2013; 288:33697-33707. [PMID: 24072706 DOI: 10.1074/jbc.m113.508283] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
As translation proceeds, nascent polypeptides pass through an exit tunnel that traverses the large ribosomal subunit. Three ribosomal proteins, termed Rpl4, Rpl17, and Rpl39 expose domains to the interior of the exit tunnel of eukaryotic ribosomes. Here we generated ribosome-bound nascent chains in a homologous yeast translation system to analyze contacts between the tunnel proteins and nascent chains. As model proteins we employed Dap2, which contains a hydrophobic signal anchor (SA) segment, and the chimera Dap2α, in which the SA was replaced with a hydrophilic segment, with the propensity to form an α-helix. Employing a newly developed FLAG exposure assay, we find that the nascent SA segment but not the hydrophilic segment adopted a stable, α-helical structure within the tunnel when the most C-terminal SA residue was separated by 14 residues from the peptidyl transferase center. Using UV cross-linking, antibodies specifically recognizing Rpl17 or Rpl39, and a His6-tagged version of Rpl4, we established that all three tunnel proteins of yeast contact the SA, whereas only Rpl4 and Rpl39 also contact the hydrophilic segment. Consistent with the localization of the tunnel exposed domains of Rpl17 and Rpl39, the SA was in contact with Rpl17 in the middle region and with Rpl39 in the exit region of the tunnel. In contrast, Rpl4 was in contact with nascent chain residues throughout the ribosomal tunnel.
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Affiliation(s)
- Ying Zhang
- Institute of Biochemistry and Molecular Biology, ZBMZ Centre for Biochemistry and Molecular Cell Research, University of Freiburg, Stefan-Meier-Strasse 17, D-79104 Freiburg, Germany; Centre for Biological Signalling Studies (BIOSS), University of Freiburg, D-79104 Freiburg, Germany
| | - Tina Wölfle
- Institute of Biochemistry and Molecular Biology, ZBMZ Centre for Biochemistry and Molecular Cell Research, University of Freiburg, Stefan-Meier-Strasse 17, D-79104 Freiburg, Germany
| | - Sabine Rospert
- Institute of Biochemistry and Molecular Biology, ZBMZ Centre for Biochemistry and Molecular Cell Research, University of Freiburg, Stefan-Meier-Strasse 17, D-79104 Freiburg, Germany; Centre for Biological Signalling Studies (BIOSS), University of Freiburg, D-79104 Freiburg, Germany.
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The Not4 RING E3 Ligase: A Relevant Player in Cotranslational Quality Control. ISRN MOLECULAR BIOLOGY 2013; 2013:548359. [PMID: 27335678 PMCID: PMC4890865 DOI: 10.1155/2013/548359] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/04/2012] [Accepted: 11/21/2012] [Indexed: 12/02/2022]
Abstract
The Not4 RING E3 ligase is a subunit of the evolutionarily conserved Ccr4-Not complex. Originally identified in yeast by mutations that increase transcription, it was subsequently defined as an ubiquitin ligase. Substrates for this ligase were characterized in yeast and in metazoans. Interestingly, some substrates for this ligase are targeted for polyubiquitination and degradation, while others instead are stable monoubiquitinated proteins. The former are mostly involved in transcription, while the latter are a ribosomal protein and a ribosome-associated chaperone. Consistently, Not4 and all other subunits of the Ccr4-Not complex are present in translating ribosomes. An important function for Not4 in cotranslational quality control has emerged. In the absence of Not4, the total level of polysomes is reduced. In addition, translationally arrested polypeptides, aggregated proteins, and polyubiquitinated proteins accumulate. Its role in quality control is likely to be related on one hand to its importance for the functional assembly of the proteasome and on the other hand to its association with the RNA degradation machines. Not4 is in an ideal position to signal to degradation mRNAs whose translation has been aborted, and this defines Not4 as a key player in the quality control of newly synthesized proteins.
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Gamalinda M, Jakovljevic J, Babiano R, Talkish J, de la Cruz J, Woolford JL. Yeast polypeptide exit tunnel ribosomal proteins L17, L35 and L37 are necessary to recruit late-assembling factors required for 27SB pre-rRNA processing. Nucleic Acids Res 2012; 41:1965-83. [PMID: 23268442 PMCID: PMC3561946 DOI: 10.1093/nar/gks1272] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Ribosome synthesis involves the coordinated folding and processing of pre-rRNAs with assembly of ribosomal proteins. In eukaryotes, these events are facilitated by trans-acting factors that propel ribosome maturation from the nucleolus to the cytoplasm. However, there is a gap in understanding how ribosomal proteins configure pre-ribosomes in vivo to enable processing to occur. Here, we have examined the role of adjacent yeast r-proteins L17, L35 and L37 in folding and processing of pre-rRNAs, and binding of other proteins within assembling ribosomes. These three essential ribosomal proteins, which surround the polypeptide exit tunnel, are required for 60S subunit formation as a consequence of their role in removal of the ITS2 spacer from 27SB pre-rRNA. L17-, L35- and L37-depleted cells exhibit turnover of aberrant pre-60S assembly intermediates. Although the structure of ITS2 does not appear to be grossly affected in their absence, these three ribosomal proteins are necessary for efficient recruitment of factors required for 27SB pre-rRNA processing, namely, Nsa2 and Nog2, which associate with pre-60S ribosomal particles containing 27SB pre-rRNAs. Altogether, these data support that L17, L35 and L37 are specifically required for a recruiting step immediately preceding removal of ITS2.
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Affiliation(s)
- Michael Gamalinda
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA
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