1
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Li Z, Iida J, Shiimori M, Okamura K. Exportin-5 binding precedes 5'- and 3'-end processing of tRNA precursors in Drosophila. J Biol Chem 2024; 300:107632. [PMID: 39098529 DOI: 10.1016/j.jbc.2024.107632] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Revised: 07/16/2024] [Accepted: 07/26/2024] [Indexed: 08/06/2024] Open
Abstract
Exportin5 (Exp5) is the major miRNA nuclear export factor and recognizes structural features of pre-miRNA hairpins, while it also exports other minihelix-containing RNAs. In Drosophila, Exp5 is suggested to play a major role in tRNA export because the gene encoding the canonical tRNA export factor Exportin-t is missing in its genome. To understand molecular functions of fly Exp5, we studied the Exp5/RNA interactome in the cell line S2R + using the crosslinking and immunoprecipitation (CLIP) technology. The CLIP experiment captured known substrates such as tRNAs and miRNAs and detected candidates of novel Exp5 substrates including various mRNAs and long non-coding RNAs (lncRNAs). Some mRNAs and lncRNAs enriched PAR-CLIP tags compared to their expression levels, suggesting selective binding of Exp5 to them. Intronless mRNAs tended to enrich PAR-CLIP tags; therefore, we proposed that Exp5 might play a role in the export of specific classes of mRNAs/lncRNAs. This result suggested that Drosophila Exp5 might have a wider variety of substrates than initially thought. Surprisingly, Exp5 CLIP reads often contained sequences corresponding to the flanking 5'-leaders and 3'-trailers of tRNAs, which were thought to be removed prior to nuclear export. In fact, we found pre-tRNAs before end-processing were present in the cytoplasm, supporting the idea that tRNA end-processing is a cytoplasmic event. In summary, our results provide a genome-wide list of Exp5 substrate candidates and suggest that flies may lack a mechanism to distinguish pre-tRNAs with or without the flanking sequences.
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Affiliation(s)
- Ze Li
- Graduate School of Science and Technology, Nara Institute of Science and Technology, Ikoma, Nara, Japan
| | - Junko Iida
- Graduate School of Science and Technology, Nara Institute of Science and Technology, Ikoma, Nara, Japan
| | - Masami Shiimori
- Graduate School of Science and Technology, Nara Institute of Science and Technology, Ikoma, Nara, Japan
| | - Katsutomo Okamura
- Graduate School of Science and Technology, Nara Institute of Science and Technology, Ikoma, Nara, Japan; Temasek Life Sciences Laboratory, National University of Singapore, Singapore, Singapore.
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2
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Lv X, Zhang R, Li S, Jin X. tRNA Modifications and Dysregulation: Implications for Brain Diseases. Brain Sci 2024; 14:633. [PMID: 39061374 PMCID: PMC11274612 DOI: 10.3390/brainsci14070633] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2024] [Revised: 06/05/2024] [Accepted: 06/12/2024] [Indexed: 07/28/2024] Open
Abstract
Transfer RNAs (tRNAs) are well-known for their essential function in protein synthesis. Recent research has revealed a diverse range of chemical modifications that tRNAs undergo, which are crucial for various cellular processes. These modifications are necessary for the precise and efficient translation of proteins and also play important roles in gene expression regulation and cellular stress response. This review examines the role of tRNA modifications and dysregulation in the pathophysiology of various brain diseases, including epilepsy, stroke, neurodevelopmental disorders, brain tumors, Alzheimer's disease, and Parkinson's disease. Through a comprehensive analysis of existing research, our study aims to elucidate the intricate relationship between tRNA dysregulation and brain diseases. This underscores the critical need for ongoing exploration in this field and provides valuable insights that could facilitate the development of innovative diagnostic tools and therapeutic approaches, ultimately improving outcomes for individuals grappling with complex neurological conditions.
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Affiliation(s)
- Xinxin Lv
- School of Medicine, Nankai University, Tianjin 300071, China; (X.L.); (S.L.)
| | - Ruorui Zhang
- Dana and David Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, CA 90089, USA;
| | - Shanshan Li
- School of Medicine, Nankai University, Tianjin 300071, China; (X.L.); (S.L.)
| | - Xin Jin
- School of Medicine, Nankai University, Tianjin 300071, China; (X.L.); (S.L.)
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3
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Diaz C, Thankam FG, Agrawal DK. Karyopherins in the Remodeling of Extracellular Matrix: Implications in Tendon Injury. JOURNAL OF ORTHOPAEDICS AND SPORTS MEDICINE 2023; 5:357-374. [PMID: 37829147 PMCID: PMC10569131 DOI: 10.26502/josm.511500122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/14/2023]
Abstract
Rotator Cuff Tendinopathies (RCT) are debilitating conditions characterized by alterations in the extracellular matrix (ECM) of the shoulder tendon, resulting in pain, discomfort, and functional limitations. Specific mediators, including HIF-1α, TGF-β, MMP-9 and others have been implicated in the morphological changes observed in the tendon ECM. These mediators rely on karyopherins, a family of nuclear proteins involved in nucleo-cytoplasmic transport; however, the role of karyopherins in RCT remains understudied despite their potential role in nuclear transport mechanisms. Also, the understanding regarding the precise contributions of karyopherins in RCT holds great promise for deciphering the underlying pathophysiological mechanisms of the disease and potentially fostering the development of targeted therapeutic strategies. This article critically discusses the implications, possibilities, and perspectives of karyopherins in the pathophysiology of RCT.
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Affiliation(s)
- Connor Diaz
- University of Missouri School of Medicine, Springfield Clinical Campus, Springfield, MO 65807, USA
| | - Finosh G Thankam
- Department of Translational Research, Western University of Health Sciences, Pomona, California 91766, USA
| | - Devendra K Agrawal
- Department of Translational Research, Western University of Health Sciences, Pomona, California 91766, USA
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4
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Abstract
The study of eukaryotic tRNA processing has given rise to an explosion of new information and insights in the last several years. We now have unprecedented knowledge of each step in the tRNA processing pathway, revealing unexpected twists in biochemical pathways, multiple new connections with regulatory pathways, and numerous biological effects of defects in processing steps that have profound consequences throughout eukaryotes, leading to growth phenotypes in the yeast Saccharomyces cerevisiae and to neurological and other disorders in humans. This review highlights seminal new results within the pathways that comprise the life of a tRNA, from its birth after transcription until its death by decay. We focus on new findings and revelations in each step of the pathway including the end-processing and splicing steps, many of the numerous modifications throughout the main body and anticodon loop of tRNA that are so crucial for tRNA function, the intricate tRNA trafficking pathways, and the quality control decay pathways, as well as the biogenesis and biology of tRNA-derived fragments. We also describe the many interactions of these pathways with signaling and other pathways in the cell.
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Affiliation(s)
- Eric M Phizicky
- Department of Biochemistry and Biophysics and Center for RNA Biology, University of Rochester School of Medicine, Rochester, New York 14642, USA
| | - Anita K Hopper
- Department of Molecular Genetics and Center for RNA Biology, Ohio State University, Columbus, Ohio 43235, USA
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5
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Chatterjee K, Hopper AK. In Vivo Cross-Linking and Co-Immunoprecipitation Procedure to Analyze Nuclear tRNA Export Complexes in Yeast Cells. Methods Mol Biol 2023; 2666:115-136. [PMID: 37166661 PMCID: PMC10370246 DOI: 10.1007/978-1-0716-3191-1_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
tRNAs are small noncoding RNAs that are predominantly known for their roles in protein synthesis and also participate in numerous other functions ranging from retroviral replication to apoptosis. In eukaryotic cells, all tRNAs move bidirectionally, shuttling between the nucleus and the cytoplasm. Bidirectional nuclear-cytoplasmic tRNA trafficking requires a complex set of conserved proteins. Here, we describe an in vivo biochemical methodology in Saccharomyces cerevisiae to assess the ability of proteins implicated in tRNA nuclear export to form nuclear export complexes with tRNAs. This method employs tagged putative tRNA nuclear exporter proteins and co-immunoprecipitation of tRNA-exporter complexes using antibody-conjugated magnetic beads. Because the interaction between nuclear exporters and tRNAs may be transient, this methodology employs strategies to effectively trap tRNA-protein complexes in vivo. This pull-down method can be used to verify and characterize candidate proteins and their potential interactors implicated in tRNA nuclear-cytoplasmic trafficking.
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Affiliation(s)
- Kunal Chatterjee
- Department of Molecular Genetics, Center for RNA Biology, The Ohio State University, Columbus, OH, USA.
- Department of Biology, Wittenberg University, Springfield, OH, USA.
| | - Anita K Hopper
- Department of Molecular Genetics, Center for RNA Biology, The Ohio State University, Columbus, OH, USA.
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6
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Chatterjee K, Marshall WA, Hopper AK. Three tRNA nuclear exporters in S. cerevisiae: parallel pathways, preferences, and precision. Nucleic Acids Res 2022; 50:10140-10152. [PMID: 36099418 PMCID: PMC9508810 DOI: 10.1093/nar/gkac754] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 08/11/2022] [Accepted: 09/02/2022] [Indexed: 11/15/2022] Open
Abstract
tRNAs that are transcribed in the nucleus are exported to the cytoplasm to perform their iterative essential function in translation. However, the complex set of tRNA post-transcriptional processing and subcellular trafficking steps are not completely understood. In particular, proteins involved in tRNA nuclear export remain unknown since the canonical tRNA nuclear exportin, Los1/Exportin-t, is unessential in all tested organisms. We previously reported that budding yeast Mex67-Mtr2, a mRNA nuclear exporter, co-functions with Los1 in tRNA nuclear export. Here we employed in vivo co-purification of tRNAs with endogenously expressed nuclear exporters to document that Crm1 also is a bona fide tRNA nuclear exporter. We document that Los1, Mex67-Mtr2 and Crm1 possess individual tRNA preferences for forming nuclear export complexes with members of the 10 families of intron-containing pre-tRNAs. Remarkably, Mex67-Mtr2, but not Los1 or Crm1, is error-prone, delivering tRNAs to the cytoplasm prior to 5′ leader removal. tRNA retrograde nuclear import functions to monitor the aberrant leader-containing spliced tRNAs, returning them to the nucleus where they are degraded by 3′ to 5′ exonucleases. Overall, our work identifies a new tRNA nuclear exporter, uncovers exporter preferences for specific tRNA families, and documents contribution of tRNA nuclear import to tRNA quality control.
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Affiliation(s)
- Kunal Chatterjee
- Department of Molecular Genetics, Ohio State University, Columbus, OH 43235, USA.,Center for RNA Biology, Ohio State University, Columbus, OH 43235, USA
| | - William A Marshall
- Department of Molecular Genetics, Ohio State University, Columbus, OH 43235, USA
| | - Anita K Hopper
- Department of Molecular Genetics, Ohio State University, Columbus, OH 43235, USA.,Center for RNA Biology, Ohio State University, Columbus, OH 43235, USA
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7
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Sekulovski S, Trowitzsch S. Transfer RNA processing - from a structural and disease perspective. Biol Chem 2022; 403:749-763. [PMID: 35728022 DOI: 10.1515/hsz-2021-0406] [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: 11/02/2021] [Accepted: 05/24/2022] [Indexed: 01/05/2023]
Abstract
Transfer RNAs (tRNAs) are highly structured non-coding RNAs which play key roles in translation and cellular homeostasis. tRNAs are initially transcribed as precursor molecules and mature by tightly controlled, multistep processes that involve the removal of flanking and intervening sequences, over 100 base modifications, addition of non-templated nucleotides and aminoacylation. These molecular events are intertwined with the nucleocytoplasmic shuttling of tRNAs to make them available at translating ribosomes. Defects in tRNA processing are linked to the development of neurodegenerative disorders. Here, we summarize structural aspects of tRNA processing steps with a special emphasis on intron-containing tRNA splicing involving tRNA splicing endonuclease and ligase. Their role in neurological pathologies will be discussed. Identification of novel RNA substrates of the tRNA splicing machinery has uncovered functions unrelated to tRNA processing. Future structural and biochemical studies will unravel their mechanistic underpinnings and deepen our understanding of neurological diseases.
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Affiliation(s)
- Samoil Sekulovski
- Institute of Biochemistry, Biocenter, Goethe University Frankfurt, Max-von-Laue-Strasse 9, D-60438 Frankfurt/Main, Germany
| | - Simon Trowitzsch
- Institute of Biochemistry, Biocenter, Goethe University Frankfurt, Max-von-Laue-Strasse 9, D-60438 Frankfurt/Main, Germany
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8
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Cheung CY, Huang TT, Chow N, Zhang S, Zhao Y, Chau MP, Chan WC, Wong CCL, Boassa D, Phan S, Ellisman MH, Yates JR, Xu S, Yu Z, Zhang Y, Zhang R, Ng LL, Ko BCB. Unconventional tonicity-regulated nuclear trafficking of NFAT5 mediated by KPNB1, XPOT and RUVBL2. J Cell Sci 2022; 135:275560. [PMID: 35635291 PMCID: PMC9377714 DOI: 10.1242/jcs.259280] [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: 08/18/2021] [Accepted: 05/20/2022] [Indexed: 11/20/2022] Open
Abstract
NFAT5 is the only known mammalian tonicity-responsive transcription factor with essential role in cellular adaptation to hypertonic stress. It is also implicated in diverse physiological and pathological processes. NFAT5 activity is tightly regulated by extracellular tonicity, but the underlying mechanisms remain elusive. We demonstrated that NFAT5 enters the nucleus via the nuclear pore complex. We found that NFAT5 utilizes a unique nuclear localization signal (NFAT5-NLS) for nuclear import. siRNA screening revealed that only karyopherin β1 (KPNB1), but not karyopherin alpha, is responsible for the nuclear import of NFAT5 via direct interaction with the NFAT5-NLS. Proteomics analysis and siRNA screening further revealed that nuclear export of NFAT5 under hypotonicity is driven by Exportin-T, where the process requires RuvB-Like AAA type ATPase 2 (RUVBL2) as an indispensable chaperone. Our findings have identified an unconventional tonicity-dependent nucleocytoplasmic trafficking pathway for NFAT5, a critical step in orchestrating rapid cellular adaptation to change in extracellular tonicity. These findings offer an opportunity for the development of novel NFAT5 targeting strategies that are potentially useful for the treatment of diseases associated with NFAT5 dysregulation.
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Affiliation(s)
- Chris Y Cheung
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong, China.,State Key Laboratory of Chemical Biology and Drug Discovery, The Hong Kong Polytechnic University, Hong Kong, China
| | - Ting-Ting Huang
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong, China.,State Key Laboratory of Chemical Biology and Drug Discovery, The Hong Kong Polytechnic University, Hong Kong, China
| | - Ning Chow
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong, China.,State Key Laboratory of Chemical Biology and Drug Discovery, The Hong Kong Polytechnic University, Hong Kong, China
| | - Shuqi Zhang
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong, China.,State Key Laboratory of Chemical Biology and Drug Discovery, The Hong Kong Polytechnic University, Hong Kong, China
| | - Yanxiang Zhao
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong, China.,State Key Laboratory of Chemical Biology and Drug Discovery, The Hong Kong Polytechnic University, Hong Kong, China
| | - Mary P Chau
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong, China.,State Key Laboratory of Chemical Biology and Drug Discovery, The Hong Kong Polytechnic University, Hong Kong, China
| | - Wing Cheung Chan
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong, China.,State Key Laboratory of Chemical Biology and Drug Discovery, The Hong Kong Polytechnic University, Hong Kong, China
| | - Catherine C L Wong
- Center for Precision Medicine Muti-Omics Research, Health Science Center, Peking University, China Clinical Laboratory Department, The Cancer Hospital of the University of Chinese Academy of Sciences, Beijing, China
| | - Daniela Boassa
- Department of Neurosciences, University of California, San Diego, USA.,Center for Research in Biological Systems, National Center for Microscopy and Imaging Research, University of California, San Diego, La Jolla, California, USA
| | - Sebastien Phan
- Department of Neurosciences, University of California, San Diego, USA.,Center for Research in Biological Systems, National Center for Microscopy and Imaging Research, University of California, San Diego, La Jolla, California, USA
| | - Mark H Ellisman
- Department of Neurosciences, University of California, San Diego, USA.,Center for Research in Biological Systems, National Center for Microscopy and Imaging Research, University of California, San Diego, La Jolla, California, USA
| | - John R Yates
- Department of Chemical Physiology, The Scripps Research Institute, La Jolla, California, USA
| | - SongXiao Xu
- The Clinical Laboratory Department, The Cancer Hospital of the University of Chinese Academy of Sciences (Zhejiang Cancer Hospital), Institute of Basic Medicine and Cancer, Chinese Academy of Sciences, Hangzhou, Zhejiang, China
| | - Zicheng Yu
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong, China.,State Key Laboratory of Chemical Biology and Drug Discovery, The Hong Kong Polytechnic University, Hong Kong, China
| | - Yajing Zhang
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong, China.,State Key Laboratory of Chemical Biology and Drug Discovery, The Hong Kong Polytechnic University, Hong Kong, China
| | - Rui Zhang
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong, China.,State Key Laboratory of Chemical Biology and Drug Discovery, The Hong Kong Polytechnic University, Hong Kong, China
| | - Ling Ling Ng
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong, China.,State Key Laboratory of Chemical Biology and Drug Discovery, The Hong Kong Polytechnic University, Hong Kong, China
| | - Ben C B Ko
- Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hong Kong, China.,State Key Laboratory of Chemical Biology and Drug Discovery, The Hong Kong Polytechnic University, Hong Kong, China
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9
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Lateef OM, Akintubosun MO, Olaoba OT, Samson SO, Adamczyk M. Making Sense of "Nonsense" and More: Challenges and Opportunities in the Genetic Code Expansion, in the World of tRNA Modifications. Int J Mol Sci 2022; 23:938. [PMID: 35055121 PMCID: PMC8779196 DOI: 10.3390/ijms23020938] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Revised: 01/10/2022] [Accepted: 01/12/2022] [Indexed: 01/09/2023] Open
Abstract
The evolutional development of the RNA translation process that leads to protein synthesis based on naturally occurring amino acids has its continuation via synthetic biology, the so-called rational bioengineering. Genetic code expansion (GCE) explores beyond the natural translational processes to further enhance the structural properties and augment the functionality of a wide range of proteins. Prokaryotic and eukaryotic ribosomal machinery have been proven to accept engineered tRNAs from orthogonal organisms to efficiently incorporate noncanonical amino acids (ncAAs) with rationally designed side chains. These side chains can be reactive or functional groups, which can be extensively utilized in biochemical, biophysical, and cellular studies. Genetic code extension offers the contingency of introducing more than one ncAA into protein through frameshift suppression, multi-site-specific incorporation of ncAAs, thereby increasing the vast number of possible applications. However, different mediating factors reduce the yield and efficiency of ncAA incorporation into synthetic proteins. In this review, we comment on the recent advancements in genetic code expansion to signify the relevance of systems biology in improving ncAA incorporation efficiency. We discuss the emerging impact of tRNA modifications and metabolism in protein design. We also provide examples of the latest successful accomplishments in synthetic protein therapeutics and show how codon expansion has been employed in various scientific and biotechnological applications.
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Affiliation(s)
- Olubodun Michael Lateef
- Faculty of Chemistry, Warsaw University of Technology, 00-664 Warsaw, Poland; (O.M.L.); (M.O.A.); (S.O.S.)
| | | | - Olamide Tosin Olaoba
- Laboratory of Functional and Structural Biochemistry, Federal University of Sao Carlos, Sao Carlos 13565-905, SP, Brazil;
| | - Sunday Ocholi Samson
- Faculty of Chemistry, Warsaw University of Technology, 00-664 Warsaw, Poland; (O.M.L.); (M.O.A.); (S.O.S.)
| | - Malgorzata Adamczyk
- Faculty of Chemistry, Warsaw University of Technology, 00-664 Warsaw, Poland; (O.M.L.); (M.O.A.); (S.O.S.)
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10
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Li J, Guo Y, Deng Y, Hu L, Li B, Deng S, Zhong J, Xie L, Shi S, Hong X, Zheng X, Cai M, Li M. Subcellular Localization of Epstein-Barr Virus BLLF2 and Its Underlying Mechanisms. Front Microbiol 2021; 12:672192. [PMID: 34367081 PMCID: PMC8339435 DOI: 10.3389/fmicb.2021.672192] [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: 02/25/2021] [Accepted: 05/24/2021] [Indexed: 11/13/2022] Open
Abstract
Epstein-Barr virus (EBV), the pathogen of several human malignancies, encodes many proteins required to be transported into the nucleus for viral DNA reproduction and nucleocapsids assembly in the lytic replication cycle. Here, fluorescence microscope, mutation analysis, interspecies heterokaryon assays, co-immunoprecipitation assay, RNA interference, and Western blot were performed to explore the nuclear import mechanism of EBV encoded BLLF2 protein. BLLF2 was shown to be a nucleocytoplasmic shuttling protein neither by a chromosomal region maintenance 1 (CRM1)- nor by a transporter associated with antigen processing (TAP)-dependent pathway. Yet, BLLF2's two functional nuclear localization signals (NLSs), NLS1 (16KRQALETVPHPQNRGR31) and NLS2 (44RRPRPPVAKRRRFPR58), were identified, whereas the predicted NES was nonfunctional. Finally, BLLF2 was proven to transport into the nucleus via a Ran-dependent and importin β1-dependent pathway. This mechanism may contribute to a more extensive insight into the assembly and synthesis of EBV virions in the nucleus, thus affording a new direction for the treatment of viruses.
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Affiliation(s)
- Jingjing Li
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China.,Department of Oncology, Affiliated Hospital of Weifang Medical University, Weifang, China
| | - Yingjie Guo
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Yangxi Deng
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Li Hu
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Bolin Li
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Shenyu Deng
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Jiayi Zhong
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Li Xie
- Centralab, Shenzhen Center for Chronic Disease Control, Shenzhen, China
| | - Shaoxuan Shi
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Xuejun Hong
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Xuelong Zheng
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Mingsheng Cai
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
| | - Meili Li
- The Second Affiliated Hospital, State Key Laboratory of Respiratory Disease, Guangdong Provincial Key Laboratory of Allergy & Clinical Immunology, Guangzhou Medical University, Sino-French Hoffmann Institute, School of Basic Medical Science, Guangzhou Medical University, Guangzhou, China
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11
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Shen Q, Wang YE, Palazzo AF. Crosstalk between nucleocytoplasmic trafficking and the innate immune response to viral infection. J Biol Chem 2021; 297:100856. [PMID: 34097873 PMCID: PMC8254040 DOI: 10.1016/j.jbc.2021.100856] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2021] [Revised: 05/24/2021] [Accepted: 06/03/2021] [Indexed: 12/16/2022] Open
Abstract
The nuclear pore complex is the sole gateway connecting the nucleoplasm and cytoplasm. In humans, the nuclear pore complex is one of the largest multiprotein assemblies in the cell, with a molecular mass of ∼110 MDa and consisting of 8 to 64 copies of about 34 different nuclear pore proteins, termed nucleoporins, for a total of 1000 subunits per pore. Trafficking events across the nuclear pore are mediated by nuclear transport receptors and are highly regulated. The nuclear pore complex is also used by several RNA viruses and almost all DNA viruses to access the host cell nucleoplasm for replication. Viruses hijack the nuclear pore complex, and nuclear transport receptors, to access the nucleoplasm where they replicate. In addition, the nuclear pore complex is used by the cell innate immune system, a network of signal transduction pathways that coordinates the first response to foreign invaders, including viruses and other pathogens. Several branches of this response depend on dynamic signaling events that involve the nuclear translocation of downstream signal transducers. Mounting evidence has shown that these signaling cascades, especially those steps that involve nucleocytoplasmic trafficking events, are targeted by viruses so that they can evade the innate immune system. This review summarizes how nuclear pore proteins and nuclear transport receptors contribute to the innate immune response and highlights how viruses manipulate this cellular machinery to favor infection. A comprehensive understanding of nuclear pore proteins in antiviral innate immunity will likely contribute to the development of new antiviral therapeutic strategies.
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Affiliation(s)
- Qingtang Shen
- School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China.
| | - Yifan E Wang
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Alexander F Palazzo
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.
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12
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Nord MS, Bernis C, Carmona S, Garland DC, Travesa A, Forbes DJ. Exportins can inhibit major mitotic assembly events in vitro: membrane fusion, nuclear pore formation, and spindle assembly. Nucleus 2021; 11:178-193. [PMID: 32762441 PMCID: PMC7540616 DOI: 10.1080/19491034.2020.1798093] [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] [Indexed: 11/30/2022] Open
Abstract
Xenopus egg extracts are a powerful in vitro tool for studying complex biological processes, including nuclear reconstitution, nuclear membrane and pore assembly, and spindle assembly. Extracts have been further used to demonstrate a moonlighting regulatory role for nuclear import receptors or importins on these cell cycle assembly events. Here we show that exportins can also play a role in these events. Addition of Crm1, Exportin-t, or Exportin-5 decreased nuclear pore assembly in vitro. RanQ69L-GTP, a constitutively active form of RanGTP, ameliorated inhibition. Both Crm1 and Exportin-t inhibited fusion of nuclear membranes, again counteracted by RanQ69L-GTP. In mitotic extracts, Crm1 and Exportin-t negatively impacted spindle assembly. Pulldowns from the extracts using Crm1- or Exportin-t-beads revealed nucleoporins known to be essential for both nuclear pore and spindle assembly, with RanQ69L-GTP decreasing a subset of these target interactions. This study suggests a model where exportins, like importins, can regulate major mitotic assembly events.
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Affiliation(s)
- Matthew S Nord
- Section of Cell and Developmental Biology, Division of Biological Sciences 0347, University of California-San Diego , La Jolla, CA, USA
| | - Cyril Bernis
- Section of Cell and Developmental Biology, Division of Biological Sciences 0347, University of California-San Diego , La Jolla, CA, USA
| | - Sarah Carmona
- Section of Cell and Developmental Biology, Division of Biological Sciences 0347, University of California-San Diego , La Jolla, CA, USA
| | - Dennis C Garland
- Section of Cell and Developmental Biology, Division of Biological Sciences 0347, University of California-San Diego , La Jolla, CA, USA
| | - Anna Travesa
- Section of Cell and Developmental Biology, Division of Biological Sciences 0347, University of California-San Diego , La Jolla, CA, USA
| | - Douglass J Forbes
- Section of Cell and Developmental Biology, Division of Biological Sciences 0347, University of California-San Diego , La Jolla, CA, USA
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13
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Torrence ME, MacArthur MR, Hosios AM, Valvezan AJ, Asara JM, Mitchell JR, Manning BD. The mTORC1-mediated activation of ATF4 promotes protein and glutathione synthesis downstream of growth signals. eLife 2021; 10:e63326. [PMID: 33646118 PMCID: PMC7997658 DOI: 10.7554/elife.63326] [Citation(s) in RCA: 112] [Impact Index Per Article: 37.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2020] [Accepted: 02/26/2021] [Indexed: 12/16/2022] Open
Abstract
The mechanistic target of rapamycin complex 1 (mTORC1) stimulates a coordinated anabolic program in response to growth-promoting signals. Paradoxically, recent studies indicate that mTORC1 can activate the transcription factor ATF4 through mechanisms distinct from its canonical induction by the integrated stress response (ISR). However, its broader roles as a downstream target of mTORC1 are unknown. Therefore, we directly compared ATF4-dependent transcriptional changes induced upon insulin-stimulated mTORC1 signaling to those activated by the ISR. In multiple mouse embryo fibroblast and human cancer cell lines, the mTORC1-ATF4 pathway stimulated expression of only a subset of the ATF4 target genes induced by the ISR, including genes involved in amino acid uptake, synthesis, and tRNA charging. We demonstrate that ATF4 is a metabolic effector of mTORC1 involved in both its established role in promoting protein synthesis and in a previously unappreciated function for mTORC1 in stimulating cellular cystine uptake and glutathione synthesis.
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Affiliation(s)
- Margaret E Torrence
- Department of Molecular Metabolism, Harvard T. H. Chan School of Public HealthBostonUnited States
| | - Michael R MacArthur
- Department of Molecular Metabolism, Harvard T. H. Chan School of Public HealthBostonUnited States
- Department of Health Sciences and Technology, Swiss Federal Institute of Technology (ETH) ZurichZurichSwitzerland
| | - Aaron M Hosios
- Department of Molecular Metabolism, Harvard T. H. Chan School of Public HealthBostonUnited States
| | - Alexander J Valvezan
- Center for Advanced Biotechnology and Medicine, Department of Pharmacology, Rutgers Robert Wood Johnson Medical SchoolPiscatawayUnited States
| | - John M Asara
- Division of Signal Transduction, Beth Israel Deaconess Medical Center and Department of Medicine, Harvard Medical SchoolBostonUnited States
| | - James R Mitchell
- Department of Molecular Metabolism, Harvard T. H. Chan School of Public HealthBostonUnited States
- Department of Health Sciences and Technology, Swiss Federal Institute of Technology (ETH) ZurichZurichSwitzerland
| | - Brendan D Manning
- Department of Molecular Metabolism, Harvard T. H. Chan School of Public HealthBostonUnited States
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14
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Berg MD, Brandl CJ. Transfer RNAs: diversity in form and function. RNA Biol 2021; 18:316-339. [PMID: 32900285 PMCID: PMC7954030 DOI: 10.1080/15476286.2020.1809197] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 07/31/2020] [Accepted: 08/08/2020] [Indexed: 12/11/2022] Open
Abstract
As the adaptor that decodes mRNA sequence into protein, the basic aspects of tRNA structure and function are central to all studies of biology. Yet the complexities of their properties and cellular roles go beyond the view of tRNAs as static participants in protein synthesis. Detailed analyses through more than 60 years of study have revealed tRNAs to be a fascinatingly diverse group of molecules in form and function, impacting cell biology, physiology, disease and synthetic biology. This review analyzes tRNA structure, biosynthesis and function, and includes topics that demonstrate their diversity and growing importance.
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Affiliation(s)
- Matthew D. Berg
- Department of Biochemistry, The University of Western Ontario, London, Canada
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15
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Porat J, Kothe U, Bayfield MA. Revisiting tRNA chaperones: New players in an ancient game. RNA (NEW YORK, N.Y.) 2021; 27:rna.078428.120. [PMID: 33593999 PMCID: PMC8051267 DOI: 10.1261/rna.078428.120] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Accepted: 02/10/2021] [Indexed: 05/03/2023]
Abstract
tRNAs undergo an extensive maturation process including post-transcriptional modifications that influence secondary and tertiary interactions. Precursor and mature tRNAs lacking key modifications are often recognized as aberrant and subsequently targeted for decay, illustrating the importance of modifications in promoting structural integrity. tRNAs also rely on tRNA chaperones to promote the folding of misfolded substrates into functional conformations. The best characterized tRNA chaperone is the La protein, which interacts with nascent RNA polymerase III transcripts to promote folding and offers protection from exonucleases. More recently, certain tRNA modification enzymes have also been demonstrated to possess tRNA folding activity distinct from their catalytic activity, suggesting that they may act as tRNA chaperones. In this review, we will discuss pioneering studies relating post-transcriptional modification to tRNA stability and decay pathways, present recent advances into the mechanism by which the RNA chaperone La assists pre-tRNA maturation, and summarize emerging research directions aimed at characterizing modification enzymes as tRNA chaperones. Together, these findings shed light on the importance of tRNA folding and how tRNA chaperones, in particular, increase the fraction of nascent pre-tRNAs that adopt a folded, functional conformation.
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16
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Paci G, Caria J, Lemke EA. Cargo transport through the nuclear pore complex at a glance. J Cell Sci 2021; 134:237315. [PMID: 33495357 DOI: 10.1242/jcs.247874] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Bidirectional transport of macromolecules across the nuclear envelope is a hallmark of eukaryotic cells, in which the genetic material is compartmentalized inside the nucleus. The nuclear pore complex (NPC) is the major gateway to the nucleus and it regulates nucleocytoplasmic transport, which is key to processes including transcriptional regulation and cell cycle control. Accordingly, components of the nuclear transport machinery are often found to be dysregulated or hijacked in diseases. In this Cell Science at a Glance article and accompanying poster, we provide an overview of our current understanding of cargo transport through the NPC, from the basic transport signals and machinery to more emerging aspects, all from a 'cargo perspective'. Among these, we discuss the transport of large cargoes (>15 nm), as well as the roles of different cargo properties to nuclear transport, from size and number of bound nuclear transport receptors (NTRs), to surface and mechanical properties.
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Affiliation(s)
- Giulia Paci
- Biocentre, Johannes Gutenberg-University Mainz, Hans-Dieter-Hüsch-Weg 15, 555128 Mainz, Germany.,Institute of Molecular Biology, Ackermannweg 4, 55128 Mainz, Germany.,European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Joana Caria
- Biocentre, Johannes Gutenberg-University Mainz, Hans-Dieter-Hüsch-Weg 15, 555128 Mainz, Germany.,Institute of Molecular Biology, Ackermannweg 4, 55128 Mainz, Germany.,European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
| | - Edward A Lemke
- Biocentre, Johannes Gutenberg-University Mainz, Hans-Dieter-Hüsch-Weg 15, 555128 Mainz, Germany .,Institute of Molecular Biology, Ackermannweg 4, 55128 Mainz, Germany.,European Molecular Biology Laboratory, Meyerhofstrasse 1, 69117 Heidelberg, Germany
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17
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Nostramo RT, Hopper AK. A novel assay provides insight into tRNAPhe retrograde nuclear import and re-export in S. cerevisiae. Nucleic Acids Res 2020; 48:11577-11588. [PMID: 33074312 PMCID: PMC7672469 DOI: 10.1093/nar/gkaa879] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2020] [Revised: 09/21/2020] [Accepted: 10/07/2020] [Indexed: 12/13/2022] Open
Abstract
In eukaryotes, tRNAs are transcribed in the nucleus and subsequently exported to the cytoplasm where they serve as essential adaptor molecules in translation. However, tRNAs can be returned to the nucleus by the evolutionarily conserved process called tRNA retrograde nuclear import, before relocalization back to the cytoplasm via a nuclear re-export step. Several important functions of these latter two trafficking events have been identified, yet the pathways are largely unknown. Therefore, we developed an assay in Saccharomyces cerevisiae to identify proteins mediating tRNA retrograde nuclear import and re-export using the unique wybutosine modification of mature tRNAPhe. Our hydrochloric acid/aniline assay revealed that the karyopherin Mtr10 mediates retrograde import of tRNAPhe, constitutively and in response to amino acid deprivation, whereas the Hsp70 protein Ssa2 mediates import specifically in the latter. Furthermore, tRNAPhe is re-exported by Crm1 and Mex67, but not by the canonical tRNA exporters Los1 or Msn5. These findings indicate that the re-export process occurs in a tRNA family-specific manner. Together, this assay provides insights into the pathways for tRNAPhe retrograde import and re-export and is a tool that can be used on a genome-wide level to identify additional gene products involved in these tRNA trafficking events.
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Affiliation(s)
- Regina T Nostramo
- Department of Molecular Genetics Center for RNA Biology The Ohio State University, Columbus, OH 43210, USA
| | - Anita K Hopper
- Department of Molecular Genetics Center for RNA Biology The Ohio State University, Columbus, OH 43210, USA
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18
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Bitetto G, Di Fonzo A. Nucleo-cytoplasmic transport defects and protein aggregates in neurodegeneration. Transl Neurodegener 2020; 9:25. [PMID: 32616075 PMCID: PMC7333321 DOI: 10.1186/s40035-020-00205-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Accepted: 06/01/2020] [Indexed: 02/06/2023] Open
Abstract
In the ongoing process of uncovering molecular abnormalities in neurodegenerative diseases characterized by toxic protein aggregates, nucleo-cytoplasmic transport defects have an emerging role. Several pieces of evidence suggest a link between neuronal protein inclusions and nuclear pore complex (NPC) damage. These processes lead to oxidative stress, inefficient transcription, and aberrant DNA/RNA maintenance. The clinical and neuropathological spectrum of NPC defects is broad, ranging from physiological aging to a suite of neurodegenerative diseases. A better understanding of the shared pathways among these conditions may represent a significant step toward dissecting their underlying molecular mechanisms, opening the way to a real possibility of identifying common therapeutic targets.
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Affiliation(s)
- Giacomo Bitetto
- IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Dino Ferrari Center, Neuroscience Section, Department of Pathophysiology and Transplantation, University of Milan, Via Francesco Sforza 35, 20122, Milan, Italy
| | - Alessio Di Fonzo
- IRCCS Foundation Ca' Granda Ospedale Maggiore Policlinico, Dino Ferrari Center, Neuroscience Section, Department of Pathophysiology and Transplantation, University of Milan, Via Francesco Sforza 35, 20122, Milan, Italy.
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19
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Schaffer AE, Pinkard O, Coller JM. tRNA Metabolism and Neurodevelopmental Disorders. Annu Rev Genomics Hum Genet 2019; 20:359-387. [PMID: 31082281 DOI: 10.1146/annurev-genom-083118-015334] [Citation(s) in RCA: 57] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
tRNAs are short noncoding RNAs required for protein translation. The human genome includes more than 600 putative tRNA genes, many of which are considered redundant. tRNA transcripts are subject to tightly controlled, multistep maturation processes that lead to the removal of flanking sequences and the addition of nontemplated nucleotides. Furthermore, tRNAs are highly structured and posttranscriptionally modified. Together, these unique features have impeded the adoption of modern genomics and transcriptomics technologies for tRNA studies. Nevertheless, it has become apparent from human neurogenetic research that many tRNA biogenesis proteins cause brain abnormalities and other neurological disorders when mutated. The cerebral cortex, cerebellum, and peripheral nervous system show defects, impairment, and degeneration upon tRNA misregulation, suggesting that they are particularly sensitive to changes in tRNA expression or function. An integrated approach to identify tRNA species and contextually characterize tRNA function will be imperative to drive future tool development and novel therapeutic design for tRNA-associated disorders.
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Affiliation(s)
- Ashleigh E Schaffer
- Department of Genetics and Genome Sciences and Center for RNA Science and Therapeutics, Case Western Reserve University, Cleveland, Ohio 44106, USA;
| | - Otis Pinkard
- Department of Genetics and Genome Sciences and Center for RNA Science and Therapeutics, Case Western Reserve University, Cleveland, Ohio 44106, USA;
| | - Jeffery M Coller
- Department of Genetics and Genome Sciences and Center for RNA Science and Therapeutics, Case Western Reserve University, Cleveland, Ohio 44106, USA;
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20
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Hopper AK, Nostramo RT. tRNA Processing and Subcellular Trafficking Proteins Multitask in Pathways for Other RNAs. Front Genet 2019; 10:96. [PMID: 30842788 PMCID: PMC6391926 DOI: 10.3389/fgene.2019.00096] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 01/29/2019] [Indexed: 01/28/2023] Open
Abstract
This article focuses upon gene products that are involved in tRNA biology, with particular emphasis upon post-transcriptional RNA processing and nuclear-cytoplasmic subcellular trafficking. Rather than analyzing these proteins solely from a tRNA perspective, we explore the many overlapping functions of the processing enzymes and proteins involved in subcellular traffic. Remarkably, there are numerous examples of conserved gene products and RNP complexes involved in tRNA biology that multitask in a similar fashion in the production and/or subcellular trafficking of other RNAs, including small structured RNAs such as snRNA, snoRNA, 5S RNA, telomerase RNA, and SRP RNA as well as larger unstructured RNAs such as mRNAs and RNA-protein complexes such as ribosomes. Here, we provide examples of steps in tRNA biology that are shared with other RNAs including those catalyzed by enzymes functioning in 5' end-processing, pseudoU nucleoside modification, and intron splicing as well as steps regulated by proteins functioning in subcellular trafficking. Such multitasking highlights the clever mechanisms cells employ for maximizing their genomes.
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Affiliation(s)
- Anita K Hopper
- Department of Molecular Genetics, Center for RNA Biology, Ohio State University, Columbus, OH, United States
| | - Regina T Nostramo
- Department of Molecular Genetics, Center for RNA Biology, Ohio State University, Columbus, OH, United States
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21
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Fu X, Liang C, Li F, Wang L, Wu X, Lu A, Xiao G, Zhang G. The Rules and Functions of Nucleocytoplasmic Shuttling Proteins. Int J Mol Sci 2018; 19:ijms19051445. [PMID: 29757215 PMCID: PMC5983729 DOI: 10.3390/ijms19051445] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2018] [Revised: 04/16/2018] [Accepted: 04/17/2018] [Indexed: 12/14/2022] Open
Abstract
Biological macromolecules are the basis of life activities. There is a separation of spatial dimension between DNA replication and RNA biogenesis, and protein synthesis, which is an interesting phenomenon. The former occurs in the cell nucleus, while the latter in the cytoplasm. The separation requires protein to transport across the nuclear envelope to realize a variety of biological functions. Nucleocytoplasmic transport of protein including import to the nucleus and export to the cytoplasm is a complicated process that requires involvement and interaction of many proteins. In recent years, many studies have found that proteins constantly shuttle between the cytoplasm and the nucleus. These shuttling proteins play a crucial role as transport carriers and signal transduction regulators within cells. In this review, we describe the mechanism of nucleocytoplasmic transport of shuttling proteins and summarize some important diseases related shuttling proteins.
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Affiliation(s)
- Xuekun Fu
- Department of Biology and Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Southern University of Science and Technology, Shenzhen 518055, China.
- Law Sau Fai Institute for Advancing Translational Medicine in Bone and Joint Diseases, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
| | - Chao Liang
- Law Sau Fai Institute for Advancing Translational Medicine in Bone and Joint Diseases, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
- Institute of Integrated Bioinfomedicine and Translational Science, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
- Institute of Precision Medicine and Innovative Drug Discovery, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
- Shenzhen Lab of Combinatorial Compounds and Targeted Drug Delivery, HKBU Institute of Research and Continuing Education, Shenzhen 518057, China.
| | - Fangfei Li
- Law Sau Fai Institute for Advancing Translational Medicine in Bone and Joint Diseases, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
- Institute of Integrated Bioinfomedicine and Translational Science, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
- Institute of Precision Medicine and Innovative Drug Discovery, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
- Shenzhen Lab of Combinatorial Compounds and Targeted Drug Delivery, HKBU Institute of Research and Continuing Education, Shenzhen 518057, China.
| | - Luyao Wang
- Law Sau Fai Institute for Advancing Translational Medicine in Bone and Joint Diseases, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
- Institute of Integrated Bioinfomedicine and Translational Science, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
- Institute of Precision Medicine and Innovative Drug Discovery, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
- Shenzhen Lab of Combinatorial Compounds and Targeted Drug Delivery, HKBU Institute of Research and Continuing Education, Shenzhen 518057, China.
| | - Xiaoqiu Wu
- Law Sau Fai Institute for Advancing Translational Medicine in Bone and Joint Diseases, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
- Institute of Integrated Bioinfomedicine and Translational Science, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
- Institute of Precision Medicine and Innovative Drug Discovery, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
- Shenzhen Lab of Combinatorial Compounds and Targeted Drug Delivery, HKBU Institute of Research and Continuing Education, Shenzhen 518057, China.
| | - Aiping Lu
- Law Sau Fai Institute for Advancing Translational Medicine in Bone and Joint Diseases, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
- Institute of Integrated Bioinfomedicine and Translational Science, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
- Institute of Precision Medicine and Innovative Drug Discovery, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
- Shenzhen Lab of Combinatorial Compounds and Targeted Drug Delivery, HKBU Institute of Research and Continuing Education, Shenzhen 518057, China.
| | - Guozhi Xiao
- Department of Biology and Guangdong Provincial Key Laboratory of Cell Microenvironment and Disease Research, Southern University of Science and Technology, Shenzhen 518055, China.
- Department of Orthopedic Surgery, Rush University Medical Center, Chicago, IL 60612, USA.
| | - Ge Zhang
- Law Sau Fai Institute for Advancing Translational Medicine in Bone and Joint Diseases, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
- Institute of Integrated Bioinfomedicine and Translational Science, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
- Institute of Precision Medicine and Innovative Drug Discovery, School of Chinese Medicine, Hong Kong Baptist University, Hong Kong, China.
- Shenzhen Lab of Combinatorial Compounds and Targeted Drug Delivery, HKBU Institute of Research and Continuing Education, Shenzhen 518057, China.
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22
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Blewett NH, Maraia RJ. La involvement in tRNA and other RNA processing events including differences among yeast and other eukaryotes. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2018; 1861:361-372. [PMID: 29397330 DOI: 10.1016/j.bbagrm.2018.01.013] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Revised: 12/29/2017] [Accepted: 01/17/2018] [Indexed: 10/25/2022]
Abstract
The conserved nuclear RNA-binding factor known as La protein arose in an ancient eukaryote, phylogenetically associated with another eukaryotic hallmark, synthesis of tRNA by RNA polymerase III (RNAP III). Because 3'-oligo(U) is the sequence-specific signal for transcription termination by RNAP III as well as the high affinity binding site for La, the latter is linked to the intranuclear posttranscriptional processing of eukaryotic precursor-tRNAs. The pre-tRNA processing pathway must accommodate a variety of substrates that are destined for both common steps as well as tRNA-specific events. The order of intranuclear pre-tRNA processing steps is mediated in part by three activities derived from interaction with La protein: 3'-end protection from untimely decay by 3' exonucleases, nuclear retention and chaperone activity that helps prevent pre-tRNA misfolding and mischanneling into offline pathways. A focus of this perspective will be on differences between yeast and mammals in the subcellular partitioning of pre-tRNA intermediates and differential interactions with La. We review how this is most relevant to pre-tRNA splicing which occurs in the cytoplasm of yeasts but in nuclei of higher eukaryotes. Also divergent is La architecture, comprised of three RNA-binding domains in organisms in all examined branches of the eukaryal tree except yeast, which have lost the C-terminal RNA recognition motif-2α (RRM2α) domain. We also review emerging data that suggest mammalian La interacts with nuclear pre-tRNA splicing intermediates and may impact this branch of the tRNA maturation pathway. Finally, because La is involved in intranuclear tRNA biogenesis we review relevant aspects of tRNA-associated neurodegenerative diseases. This article is part of a Special Issue entitled: SI: Regulation of tRNA synthesis and modification in physiological conditions and disease edited by Dr. Boguta Magdalena.
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Affiliation(s)
- Nathan H Blewett
- Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Richard J Maraia
- Intramural Research Program, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA; Commissioned Corps, U.S. Public Health Service, Rockville, MD, USA.
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23
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Chatterjee K, Nostramo RT, Wan Y, Hopper AK. tRNA dynamics between the nucleus, cytoplasm and mitochondrial surface: Location, location, location. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2018; 1861:373-386. [PMID: 29191733 PMCID: PMC5882565 DOI: 10.1016/j.bbagrm.2017.11.007] [Citation(s) in RCA: 60] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Revised: 11/19/2017] [Accepted: 11/23/2017] [Indexed: 01/20/2023]
Abstract
Although tRNAs participate in the essential function of protein translation in the cytoplasm, tRNA transcription and numerous processing steps occur in the nucleus. This subcellular separation between tRNA biogenesis and function requires that tRNAs be efficiently delivered to the cytoplasm in a step termed "primary tRNA nuclear export". Surprisingly, tRNA nuclear-cytoplasmic traffic is not unidirectional, but, rather, movement is bidirectional. Cytoplasmic tRNAs are imported back to the nucleus by the "tRNA retrograde nuclear import" step which is conserved from budding yeast to vertebrate cells and has been hijacked by viruses, such as HIV, for nuclear import of the viral reverse transcription complex in human cells. Under appropriate environmental conditions cytoplasmic tRNAs that have been imported into the nucleus return to the cytoplasm via the 3rd nuclear-cytoplasmic shuttling step termed "tRNA nuclear re-export", that again is conserved from budding yeast to vertebrate cells. We describe the 3 steps of tRNA nuclear-cytoplasmic movements and their regulation. There are multiple tRNA nuclear export and import pathways. The different tRNA nuclear exporters appear to possess substrate specificity leading to the tantalizing possibility that the cellular proteome may be regulated at the level of tRNA nuclear export. Moreover, in some organisms, such as budding yeast, the pre-tRNA splicing heterotetrameric endonuclease (SEN), which removes introns from pre-tRNAs, resides on the cytoplasmic surface of the mitochondria. Therefore, we also describe the localization of the SEN complex to mitochondria and splicing of pre-tRNA on mitochondria, which occurs prior to the participation of tRNAs in protein translation. This article is part of a Special Issue entitled: SI: Regulation of tRNA synthesis and modification in physiological conditions and disease edited by Dr. Boguta Magdalena.
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Affiliation(s)
- Kunal Chatterjee
- The Ohio State University Comprehensive Cancer Research Center, United States; Department of Molecular Genetics, The Ohio State University, United States; Center for RNA Biology, The Ohio State University, United States
| | - Regina T Nostramo
- Department of Molecular Genetics, The Ohio State University, United States; Center for RNA Biology, The Ohio State University, United States
| | - Yao Wan
- The Ohio State University Comprehensive Cancer Research Center, United States; Department of Molecular Genetics, The Ohio State University, United States; Center for RNA Biology, The Ohio State University, United States
| | - Anita K Hopper
- Department of Molecular Genetics, The Ohio State University, United States; Center for RNA Biology, The Ohio State University, United States.
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24
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A tRNA's fate is decided at its 3' end: Collaborative actions of CCA-adding enzyme and RNases involved in tRNA processing and degradation. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2018; 1861:433-441. [PMID: 29374586 DOI: 10.1016/j.bbagrm.2018.01.012] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Revised: 01/15/2018] [Accepted: 01/19/2018] [Indexed: 02/07/2023]
Abstract
tRNAs are key players in translation and are additionally involved in a wide range of distinct cellular processes. The vital importance of tRNAs becomes evident in numerous diseases that are linked to defective tRNA molecules. It is therefore not surprising that the structural intactness of tRNAs is continuously scrutinized and defective tRNAs are eliminated. In this process, erroneous tRNAs are tagged with single-stranded RNA sequences that are recognized by degrading exonucleases. Recent discoveries have revealed that the CCA-adding enzyme - actually responsible for the de novo synthesis of the 3'-CCA end - plays an indispensable role in tRNA quality control by incorporating a second CCA triplet that is recognized as a degradation tag. In this review, we give an update on the latest findings regarding tRNA quality control that turns out to represent an interplay of the CCA-adding enzyme and RNases involved in tRNA degradation and maturation. In particular, the RNase-induced turnover of the CCA end is now recognized as a trigger for the CCA-adding enzyme to repeatedly scrutinize the structural intactness of a tRNA. This article is part of a Special Issue entitled: SI: Regulation of tRNA synthesis and modification in physiological conditions and disease edited by Dr. Boguta Magdalena.
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25
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Chatterjee K, Majumder S, Wan Y, Shah V, Wu J, Huang HY, Hopper AK. Sharing the load: Mex67-Mtr2 cofunctions with Los1 in primary tRNA nuclear export. Genes Dev 2017; 31:2186-2198. [PMID: 29212662 PMCID: PMC5749166 DOI: 10.1101/gad.305904.117] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2017] [Accepted: 11/06/2017] [Indexed: 11/24/2022]
Abstract
Here, Chatterjee et al. describe a novel tRNA nuclear export pathway that functions in parallel to the tRNA nuclear exporter Los1. They provide molecular, genetic, cytological, and biochemical evidence that the Mex67–Mtr2 (TAP–p15) heterodimer, best characterized for its essential role in mRNA nuclear export, cofunctions with Los1 in tRNA nuclear export. Eukaryotic transfer RNAs (tRNAs) are exported from the nucleus, their site of synthesis, to the cytoplasm, their site of function for protein synthesis. The evolutionarily conserved β-importin family member Los1 (Exportin-t) has been the only exporter known to execute nuclear export of newly transcribed intron-containing pre-tRNAs. Interestingly, LOS1 is unessential in all tested organisms. As tRNA nuclear export is essential, we previously interrogated the budding yeast proteome to identify candidates that function in tRNA nuclear export. Here, we provide molecular, genetic, cytological, and biochemical evidence that the Mex67–Mtr2 (TAP–p15) heterodimer, best characterized for its essential role in mRNA nuclear export, cofunctions with Los1 in tRNA nuclear export. Inactivation of Mex67 or Mtr2 leads to rapid accumulation of end-matured unspliced tRNAs in the nucleus. Remarkably, merely fivefold overexpression of Mex67–Mtr2 can substitute for Los1 in los1Δ cells. Moreover, in vivo coimmunoprecipitation assays with tagged Mex67 document that the Mex67 binds tRNAs. Our data also show that tRNA exporters surprisingly exhibit differential tRNA substrate preferences. The existence of multiple tRNA exporters, each with different tRNA preferences, may indicate that the proteome can be regulated by tRNA nuclear export. Thus, our data show that Mex67–Mtr2 functions in primary nuclear export for a subset of yeast tRNAs.
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Affiliation(s)
- Kunal Chatterjee
- The Ohio State University Comprehensive Cancer Research Center, The Ohio State University, Columbus, Ohio 43210, USA.,Department of Molecular Genetics, The Ohio State University, Columbus, Ohio 43210, USA.,Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA
| | - Shubhra Majumder
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio 43210, USA.,Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA
| | - Yao Wan
- The Ohio State University Comprehensive Cancer Research Center, The Ohio State University, Columbus, Ohio 43210, USA.,Department of Molecular Genetics, The Ohio State University, Columbus, Ohio 43210, USA.,Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA
| | - Vijay Shah
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio 43210, USA
| | - Jingyan Wu
- The Ohio State University Comprehensive Cancer Research Center, The Ohio State University, Columbus, Ohio 43210, USA.,Department of Molecular Genetics, The Ohio State University, Columbus, Ohio 43210, USA.,Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA
| | - Hsiao-Yun Huang
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio 43210, USA.,Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA
| | - Anita K Hopper
- Department of Molecular Genetics, The Ohio State University, Columbus, Ohio 43210, USA.,Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA
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26
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Abstract
Numerous surveillance pathways sculpt eukaryotic transcriptomes by degrading unneeded, defective, and potentially harmful noncoding RNAs (ncRNAs). Because aberrant and excess ncRNAs are largely degraded by exoribonucleases, a key characteristic of these RNAs is an accessible, protein-free 5' or 3' end. Most exoribonucleases function with cofactors that recognize ncRNAs with accessible 5' or 3' ends and/or increase the availability of these ends. Noncoding RNA surveillance pathways were first described in budding yeast, and there are now high-resolution structures of many components of the yeast pathways and significant mechanistic understanding as to how they function. Studies in human cells are revealing the ways in which these pathways both resemble and differ from their yeast counterparts, and are also uncovering numerous pathways that lack equivalents in budding yeast. In this review, we describe both the well-studied pathways uncovered in yeast and the new concepts that are emerging from studies in mammalian cells. We also discuss the ways in which surveillance pathways compete with chaperone proteins that transiently protect nascent ncRNA ends from exoribonucleases, with partner proteins that sequester these ends within RNPs, and with end modification pathways that protect the ends of some ncRNAs from nucleases.
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Affiliation(s)
- Cedric Belair
- RNA Biology Laboratory, Center for Cancer Research, National Cancer Institute , National Institutes of Health , Frederick , Maryland 21702 , United States
| | - Soyeong Sim
- RNA Biology Laboratory, Center for Cancer Research, National Cancer Institute , National Institutes of Health , Frederick , Maryland 21702 , United States
| | - Sandra L Wolin
- RNA Biology Laboratory, Center for Cancer Research, National Cancer Institute , National Institutes of Health , Frederick , Maryland 21702 , United States
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27
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Kessler AC, Silveira d'Almeida G, Alfonzo JD. The role of intracellular compartmentalization on tRNA processing and modification. RNA Biol 2017; 15:554-566. [PMID: 28850002 DOI: 10.1080/15476286.2017.1371402] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Abstract
A signature of most eukaryotic cells is the presence of intricate membrane systems. Intracellular organization presumably evolved to provide order, and add layers for regulation of intracellular processes; compartmentalization also forcibly led to the appearance of sophisticated transport systems. With nucleus-encoded tRNAs, it led to the uncoupling of tRNA synthesis from many of the maturation steps it undergoes. It is now clear that tRNAs are actively transported across intracellular membranes and at any point, in any compartment, they can be post-transcriptionally modified; modification enzymes themselves may localize to any of the genome-containing compartments. In the following pages, we describe a number of well-known examples of how intracellular compartmentalization of tRNA processing and modification activities impact the function and fate of tRNAs. We raise the possibility that rates of intracellular transport may influence the level of modification and as such increase the diversity of differentially modified tRNAs in cells.
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Affiliation(s)
- Alan C Kessler
- a Department of Microbiology , The Ohio State University , Columbus , Ohio , USA.,b The Center for RNA Biology , The Ohio State University , Columbus , Ohio , USA
| | - Gabriel Silveira d'Almeida
- a Department of Microbiology , The Ohio State University , Columbus , Ohio , USA.,b The Center for RNA Biology , The Ohio State University , Columbus , Ohio , USA
| | - Juan D Alfonzo
- a Department of Microbiology , The Ohio State University , Columbus , Ohio , USA.,b The Center for RNA Biology , The Ohio State University , Columbus , Ohio , USA.,c The Ohio State Biochemistry Program , The Ohio State University , Columbus, Ohio , USA
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28
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Rohilla KJ, Gagnon KT. RNA biology of disease-associated microsatellite repeat expansions. Acta Neuropathol Commun 2017; 5:63. [PMID: 28851463 PMCID: PMC5574247 DOI: 10.1186/s40478-017-0468-y] [Citation(s) in RCA: 47] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2017] [Accepted: 08/22/2017] [Indexed: 12/13/2022] Open
Abstract
Microsatellites, or simple tandem repeat sequences, occur naturally in the human genome and have important roles in genome evolution and function. However, the expansion of microsatellites is associated with over two dozen neurological diseases. A common denominator among the majority of these disorders is the expression of expanded tandem repeat-containing RNA, referred to as xtrRNA in this review, which can mediate molecular disease pathology in multiple ways. This review focuses on the potential impact that simple tandem repeat expansions can have on the biology and metabolism of RNA that contain them and underscores important gaps in understanding. Merging the molecular biology of repeat expansion disorders with the current understanding of RNA biology, including splicing, transcription, transport, turnover and translation, will help clarify mechanisms of disease and improve therapeutic development.
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29
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Ederle H, Dormann D. TDP-43 and FUS en route from the nucleus to the cytoplasm. FEBS Lett 2017; 591:1489-1507. [PMID: 28380257 DOI: 10.1002/1873-3468.12646] [Citation(s) in RCA: 110] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2017] [Revised: 03/24/2017] [Accepted: 04/02/2017] [Indexed: 12/13/2022]
Abstract
Misfolded or mislocalized RNA-binding proteins (RBPs) and, consequently, altered mRNA processing, can cause neuronal dysfunction, eventually leading to neurodegeneration. Two prominent examples are the RBPs TAR DNA-binding protein of 43 kDa (TDP-43) and fused in sarcoma (FUS), which form pathological messenger ribonucleoprotein aggregates in patients suffering from amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), two devastating neurodegenerative disorders. Here, we review the multiple functions of TDP-43 and FUS in mRNA processing, both in the nucleus and in the cytoplasm. We discuss how TDP-43 and FUS may exit the nucleus and how defects in both nuclear and cytosolic mRNA processing events, and possibly nuclear export defects, may contribute to neurodegeneration and ALS/FTD pathogenesis.
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Affiliation(s)
- Helena Ederle
- BioMedical Center (BMC), Ludwig-Maximilians-University Munich, Planegg-Martinsried, Germany.,Graduate School of Systemic Neurosciences (GSN), Planegg-Martinsried, Germany
| | - Dorothee Dormann
- BioMedical Center (BMC), Ludwig-Maximilians-University Munich, Planegg-Martinsried, Germany.,Graduate School of Systemic Neurosciences (GSN), Planegg-Martinsried, Germany.,Munich Cluster for Systems Neurology (SyNergy), Germany
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30
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Fischetto R, Palumbo O, Ortolani F, Palumbo P, Leone MP, Causio FA, Pesce S, Digilio MC, Carella M, Papadia F. Clinical and molecular characterization of a second family with the 12q14 microdeletion syndrome and review of the literature. Am J Med Genet A 2017; 173:1922-1930. [PMID: 28407409 DOI: 10.1002/ajmg.a.38253] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 03/16/2017] [Indexed: 11/11/2022]
Abstract
The 12q14 microdeletion syndrome is a rare condition characterized by low birth weight, failure to thrive, short stature, learning disabilities, and osteopoikilosis. To date, 20 cases of 12q14 deletion have been reported in the literature, displaying both phenotypic than genetic variability. We report on three familial cases, a mother and two brothers, with severe short stature. The mother and elder brother presented with osteopoikilosis while the younger brother had severe short stature and developmental delay. SNP array analysis revealed a 1.9 Mb heterozygous 12q14.2q14.3 deletion in all three patients encompassing 14 genes and 3 miRNAs. In addition, the younger brother carried a paternal 11q13.4 duplication including the SHANK2 gene. This latter patient was investigated for developmental delay and did not show osteopoikilosis, confirming the role of age in the clinical presentation of this condition. To the best of our knowledge, this is the second family described with the syndrome. Comparing the clinical and molecular data of our patients with those previously reported we performed a detailed genotype-phenotype correlation confirming the association between growth retardation and osteopoikilosis when the rearrangement includes both LEMD3 and HMGA2 genes. In addition, we suggest the XPOT, TBK1, WIF1 genes as candidates for the clinical features observed in our patients and discuss for the first time the possible involvement of some microRNAs, when deleted, in the etiology of the phenotypes in 12q14 microdeletion syndrome patients. We expect the interpretation of our findings to be useful both from a molecular point of view and for genetic counseling.
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Affiliation(s)
- Rita Fischetto
- U.O.C. Malattie Metaboliche Genetica Medica, PO Giovanni XXIII, A.O.U. Policlinico Consorziale, Bari, Italy.,Istituto di Biologia e Genetica Generale, Medicina e Chirurgia, Università degli Studi di Bari "Aldo Moro", Bari, Italy
| | - Orazio Palumbo
- Laboratorio di Genetica Medica, IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo (FG), Italy
| | - Federica Ortolani
- U.O.C. Malattie Metaboliche Genetica Medica, PO Giovanni XXIII, A.O.U. Policlinico Consorziale, Bari, Italy
| | - Pietro Palumbo
- Laboratorio di Genetica Medica, IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo (FG), Italy
| | - Maria Pia Leone
- Laboratorio di Genetica Medica, IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo (FG), Italy.,Dipartimento di Scienze del suolo, della pianta e degli alimenti, Università degli Studi di Bari "Aldo Moro", Bari, Italy
| | - Francesco Andrea Causio
- Istituto di Patologia Generale, Facoltà di Medicina e Chirurgia, Università Cattolica Sacro Cuore, Roma, Italy
| | - Sabino Pesce
- U.O.C. Malattie Metaboliche Genetica Medica, PO Giovanni XXIII, A.O.U. Policlinico Consorziale, Bari, Italy
| | | | - Massimo Carella
- Laboratorio di Genetica Medica, IRCCS Casa Sollievo della Sofferenza, San Giovanni Rotondo (FG), Italy
| | - Francesco Papadia
- U.O.C. Malattie Metaboliche Genetica Medica, PO Giovanni XXIII, A.O.U. Policlinico Consorziale, Bari, Italy
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31
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Gupta A, Kailasam S, Bansal M. Insights into the Structural Dynamics of Nucleocytoplasmic Transport of tRNA by Exportin-t. Biophys J 2016; 110:1264-79. [PMID: 27028637 DOI: 10.1016/j.bpj.2016.02.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Revised: 01/21/2016] [Accepted: 02/05/2016] [Indexed: 12/29/2022] Open
Abstract
Exportin-t (Xpot) transports mature 5'- and 3'-end processed tRNA from the nucleus to the cytoplasm by associating with a small G-protein Ran (RAs-related nuclear protein), in the nucleus. The release of tRNA in cytoplasm involves RanGTP hydrolysis. Despite the availability of crystal structures of nuclear and cytosolic forms of Xpot, the molecular details regarding the sequential events leading to tRNA release and subsequent conformational changes occurring in Xpot remain unknown. We have performed a combination of classical all-atom and accelerated molecular dynamics simulations on a set of complexes involving Xpot to study a range of features including conformational flexibility of free and cargo-bound Xpot and functionally critical contacts between Xpot and its cargo. The systems investigated include free Xpot and its different complexes, bound either to Ran (GTP/GDP) or tRNA or both. This approach provided a statistically reliable estimate of structural dynamics of Xpot after cargo release. The mechanistic basis for Xpot opening after cargo release has been explained in terms of dynamic structural hinges, about which neighboring region could be displaced to facilitate the nuclear to cytosolic state transition. Post-RanGTP hydrolysis, a cascade of events including local conformational change in RanGTP and loss of critical contacts at Xpot/tRNA interface suggest factors responsible for eventual release of tRNA. The level of flexibility in different Xpot complexes varied depending on the arrangement of individual HEAT repeats. Current study provides one of the most comprehensive and robust analysis carried out on this protein using molecular dynamics schemes.
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Affiliation(s)
- Asmita Gupta
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka, India
| | | | - Manju Bansal
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, Karnataka, India.
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32
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Mu J, Zhang Y, Hu Y, Hu X, Zhou Y, Zhao H, Pei R, Wu C, Chen J, Zhao H, Yang K, van Oers MM, Chen X, Wang Y. Autographa californica Multiple Nucleopolyhedrovirus Ac34 Protein Retains Cellular Actin-Related Protein 2/3 Complex in the Nucleus by Subversion of CRM1-Dependent Nuclear Export. PLoS Pathog 2016; 12:e1005994. [PMID: 27802336 PMCID: PMC5089780 DOI: 10.1371/journal.ppat.1005994] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2016] [Accepted: 10/12/2016] [Indexed: 12/21/2022] Open
Abstract
Actin, nucleation-promoting factors (NPFs), and the actin-related protein 2/3 complex (Arp2/3) are key elements of the cellular actin polymerization machinery. With nuclear actin polymerization implicated in ever-expanding biological processes and the discovery of the nuclear import mechanisms of actin and NPFs, determining Arp2/3 nucleo-cytoplasmic shuttling mechanism is important for understanding the function of nuclear actin. A unique feature of alphabaculovirus infection of insect cells is the robust nuclear accumulation of Arp2/3, which induces actin polymerization in the nucleus to assist in virus replication. We found that Ac34, a viral late gene product encoded by the alphabaculovirus Autographa californica multiple nucleopolyhedrovirus (AcMNPV), is involved in Arp2/3 nuclear accumulation during virus infection. Further assays revealed that the subcellular distribution of Arp2/3 under steady-state conditions is controlled by chromosomal maintenance 1 (CRM1)-dependent nuclear export. Upon AcMNPV infection, Ac34 inhibits CRM1 pathway and leads to Arp2/3 retention in the nucleus.
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Affiliation(s)
- Jingfang Mu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Yongli Zhang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Yangyang Hu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Xue Hu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Yuan Zhou
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - He Zhao
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Rongjuan Pei
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Chunchen Wu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Jizheng Chen
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Han Zhao
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Kai Yang
- State Key Laboratory of Biocontrol, Sun Yat-sen University, Guangzhou, China
| | | | - Xinwen Chen
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
| | - Yun Wang
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, China
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33
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Mahipal A, Malafa M. Importins and exportins as therapeutic targets in cancer. Pharmacol Ther 2016; 164:135-43. [PMID: 27113410 DOI: 10.1016/j.pharmthera.2016.03.020] [Citation(s) in RCA: 110] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 03/08/2016] [Indexed: 01/01/2023]
Abstract
The nuclear transport proteins, importins and exportins (karyopherin-β proteins), may play an important role in cancer by transporting key mediators of oncogenesis across the nuclear membrane in cancer cells. During nucleocytoplasmic transport of tumor suppressor proteins and cell cycle regulators during the processing of these proteins, aberrant cellular growth signaling and inactivation of apoptosis can occur, both critical to growth and development of tumors. Karyopherin-β proteins bind to these cargo proteins and RanGTP for active transport across the nuclear membrane through the nuclear pore complex. Importins and exportins are overexpressed in multiple tumors including melanoma, pancreatic, breast, colon, gastric, prostate, esophageal, lung cancer, and lymphomas. Furthermore, some of the karyopherin-β proteins such as exportin-1 have been implicated in drug resistance in cancer. Importin and exportin inhibitors are being considered as therapeutic targets against cancer and have shown preclinical anticancer activity. Moreover, synergistic activity has been observed with various chemotherapeutic and targeted agents. However, clinical development of the exportin-1 inhibitor leptomycin B was stopped due to adverse events, including vomiting, anorexia, and dehydration. Selinexor, a selective nuclear export inhibitor, is being tested in multiple clinical trials both as a single agent and in combination with chemotherapy. Selinexor has demonstrated clinical activity in multiple cancers, especially acute myelogenous leukemia and multiple myeloma. The roles of other importin and exportin inhibitors still need to be investigated clinically. Targeting the key mediators of nucleocytoplasmic transport in cancer cells represents a novel strategy in cancer intervention with the potential to significantly affect outcomes.
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Affiliation(s)
- Amit Mahipal
- Department of Oncology, Mayo Clinic, Rochester, MN 55905, United States
| | - Mokenge Malafa
- Department of Gastrointestinal Oncology, H. Lee Moffitt Cancer Center & Research Institute, Tampa, FL 33612, United States.
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34
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Tauchert MJ, Hémonnot C, Neumann P, Köster S, Ficner R, Dickmanns A. Impact of the crystallization condition on importin-β conformation. ACTA CRYSTALLOGRAPHICA SECTION D-STRUCTURAL BIOLOGY 2016; 72:705-17. [DOI: 10.1107/s2059798316004940] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/02/2015] [Accepted: 03/23/2016] [Indexed: 11/10/2022]
Abstract
In eukaryotic cells, the exchange of macromolecules between the nucleus and cytoplasm is highly selective and requires specialized soluble transport factors. Many of them belong to the importin-β superfamily, the members of which share an overall superhelical structure owing to the tandem arrangement of a specific motif, the HEAT repeat. This structural organization leads to great intrinsic flexibility, which in turn is a prerequisite for the interaction with a variety of proteins and for its transport function. During the passage from the aqueous cytosol into the nucleus, the receptor passes the gated channel of the nuclear pore complex filled with a protein meshwork of unknown organization, which seems to be highly selective owing to the presence of FG-repeats, which are peptides with hydrophobic patches. Here, the structural changes of free importin-β from a single organism, crystallized in polar (salt) or apolar (PEG) buffer conditions, are reported. This allowed analysis of the structural changes, which are attributable to the surrounding milieu and are not affected by bound interaction partners. The importin-β structures obtained exhibit significant conformational changes and suggest an influence of the polarity of the environment, resulting in an extended conformation in the PEG condition. The significance of this observation is supported by SAXS experiments and the analysis of other crystal structures of importin-β deposited in the Protein Data Bank.
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35
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Huang HY, Hopper AK. Multiple Layers of Stress-Induced Regulation in tRNA Biology. Life (Basel) 2016; 6:life6020016. [PMID: 27023616 PMCID: PMC4931453 DOI: 10.3390/life6020016] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2016] [Revised: 03/14/2016] [Accepted: 03/17/2016] [Indexed: 01/28/2023] Open
Abstract
tRNAs are the fundamental components of the translation machinery as they deliver amino acids to the ribosomes during protein synthesis. Beyond their essential function in translation, tRNAs also function in regulating gene expression, modulating apoptosis and several other biological processes. There are multiple layers of regulatory mechanisms in each step of tRNA biogenesis. For example, tRNA 3′ trailer processing is altered upon nutrient stress; tRNA modification is reprogrammed under various stresses; nuclear accumulation of tRNAs occurs upon nutrient deprivation; tRNA halves accumulate upon oxidative stress. Here we address how environmental stresses can affect nearly every step of tRNA biology and we describe the possible regulatory mechanisms that influence the function or expression of tRNAs under stress conditions.
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Affiliation(s)
- Hsiao-Yun Huang
- Department of Biology, Indiana University, 915 E third St., Myers 300, Bloomington, IN 47405, USA.
| | - Anita K Hopper
- Department of Molecular Genetics and Center for RNA Biology, The Ohio State University, Columbus, OH 43210, USA.
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36
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Kırlı K, Karaca S, Dehne HJ, Samwer M, Pan KT, Lenz C, Urlaub H, Görlich D. A deep proteomics perspective on CRM1-mediated nuclear export and nucleocytoplasmic partitioning. eLife 2015; 4:e11466. [PMID: 26673895 PMCID: PMC4764573 DOI: 10.7554/elife.11466] [Citation(s) in RCA: 157] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2015] [Accepted: 12/13/2015] [Indexed: 12/23/2022] Open
Abstract
CRM1 is a highly conserved, RanGTPase-driven exportin that carries proteins and RNPs from the nucleus to the cytoplasm. We now explored the cargo-spectrum of CRM1 in depth and identified surprisingly large numbers, namely >700 export substrates from the yeast S. cerevisiae, ≈1000 from Xenopus oocytes and >1050 from human cells. In addition, we quantified the partitioning of ≈5000 unique proteins between nucleus and cytoplasm of Xenopus oocytes. The data suggest new CRM1 functions in spatial control of vesicle coat-assembly, centrosomes, autophagy, peroxisome biogenesis, cytoskeleton, ribosome maturation, translation, mRNA degradation, and more generally in precluding a potentially detrimental action of cytoplasmic pathways within the nuclear interior. There are also numerous new instances where CRM1 appears to act in regulatory circuits. Altogether, our dataset allows unprecedented insights into the nucleocytoplasmic organisation of eukaryotic cells, into the contributions of an exceedingly promiscuous exportin and it provides a new basis for NES prediction.
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Affiliation(s)
- Koray Kırlı
- Department of Cellular Logistics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Samir Karaca
- Department of Cellular Logistics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Heinz Jürgen Dehne
- Department of Cellular Logistics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Matthias Samwer
- Department of Cellular Logistics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Kuan Ting Pan
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Christof Lenz
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
- Bioanalytics, Institute for Clinical Chemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Henning Urlaub
- Bioanalytical Mass Spectrometry Group, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
- Bioanalytics, Institute for Clinical Chemistry, University Medical Center Göttingen, Göttingen, Germany
| | - Dirk Görlich
- Department of Cellular Logistics, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
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37
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Sloan KE, Gleizes PE, Bohnsack MT. Nucleocytoplasmic Transport of RNAs and RNA-Protein Complexes. J Mol Biol 2015; 428:2040-59. [PMID: 26434509 DOI: 10.1016/j.jmb.2015.09.023] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2015] [Revised: 09/26/2015] [Accepted: 09/28/2015] [Indexed: 12/15/2022]
Abstract
RNAs and ribonucleoprotein complexes (RNPs) play key roles in mediating and regulating gene expression. In eukaryotes, most RNAs are transcribed, processed and assembled with proteins in the nucleus and then either function in the cytoplasm or also undergo a cytoplasmic phase in their biogenesis. This compartmentalization ensures that sequential steps in gene expression and RNP production are performed in the correct order and it allows important quality control mechanisms that prevent the involvement of aberrant RNAs/RNPs in these cellular pathways. The selective exchange of RNAs/RNPs between the nucleus and cytoplasm is enabled by nuclear pore complexes, which function as gateways between these compartments. RNA/RNP transport is facilitated by a range of nuclear transport receptors and adaptors, which are specifically recruited to their cargos and mediate interactions with nucleoporins to allow directional translocation through nuclear pore complexes. While some transport factors are only responsible for the export/import of a certain class of RNA/RNP, others are multifunctional and, in the case of large RNPs, several export factors appear to work together to bring about export. Recent structural studies have revealed aspects of the mechanisms employed by transport receptors to enable specific cargo recognition, and genome-wide approaches have provided the first insights into the diverse composition of pre-mRNPs during export. Furthermore, the regulation of RNA/RNP export is emerging as an important means to modulate gene expression under stress conditions and in disease.
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Affiliation(s)
- Katherine E Sloan
- Institute for Molecular Biology, Goettingen University Medical Department, 37073 Goettingen, Germany
| | - Pierre-Emmanuel Gleizes
- Laboratoire de Biologie Moléculaire Eucaryote, UMR 5099, Université de Toulouse-Paul Sabatier, CNRS, Toulouse, France
| | - Markus T Bohnsack
- Institute for Molecular Biology, Goettingen University Medical Department, 37073 Goettingen, Germany; Goettingen Centre for Molecular Biosciences, Georg-August-University, 37075 Goettingen, Germany.
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38
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Yoshihisa T. Nucleocytoplasmic shuttling of tRNAs and implication of the cytosolic Hsp70 system in tRNA import. Nucleus 2015; 6:339-43. [PMID: 26280499 PMCID: PMC4915482 DOI: 10.1080/19491034.2015.1082696] [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] [Indexed: 11/05/2022] Open
Abstract
tRNAs, a class of non-coding RNAs essential for translation, are unique among cytosolic RNA species in that they shuttle between the nucleus and cytoplasm during their life. Although their export from the nucleus has been studied in detail, limited information on import machinery was available. Our group recently reported that Ssa2p, one of major cytosolic Hsp70s in Saccharomyces cerevisiae, acts as a crucial factor for tRNA import upon nutrient starvation. Ssa2p can bind tRNAs and a nucleoporin directly in an ATP-sensitive manner, suggesting that it acts as a nuclear import carrier for tRNAs, like importin-β proteins. In vitro assays revealed that Ssa2p binds tRNA specifically but has preference for loosely folded tRNAs. In this Extra View, these features of Ssa2p as a new import factor is discussed with other recent findings related to nucleocytoplasmic transport of tRNAs reported from other groups.
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Affiliation(s)
- Tohru Yoshihisa
- a Graduate School of Life Science; University of Hyogo ; Ako-gun , Hyogo , Japan
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39
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Huang HY, Hopper AK. In vivo biochemical analyses reveal distinct roles of β-importins and eEF1A in tRNA subcellular traffic. Genes Dev 2015; 29:772-83. [PMID: 25838545 PMCID: PMC4387718 DOI: 10.1101/gad.258293.115] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Huang et al. developed in vivo β-importin complex co-IP assays to study the interactions of β-importins with tRNAs. Los1 (exportin-t) interacts with both unspliced and spliced tRNAs. In contrast, Msn5 (exportin-5) primarily interacts with spliced aminoacylated tRNAs. They demonstrate that Tef1/2 assembles with Msn5–tRNA complexes in a RanGTP-dependent manner. Bidirectional tRNA movement between the nucleus and the cytoplasm serves multiple biological functions. To gain a biochemical understanding of the mechanisms for tRNA subcellular dynamics, we developed in vivo β-importin complex coimmunoprecipitation (co-IP) assays using budding yeast. Our studies provide the first in vivo biochemical evidence that two β-importin family members, Los1 (exportin-t) and Msn5 (exportin-5), serve overlapping but distinct roles in tRNA nuclear export. Los1 assembles complexes with RanGTP and tRNA. Both intron-containing pre-tRNAs and spliced tRNAs, regardless of whether they are aminoacylated, assemble into Los1–RanGTP complexes, documenting that Los1 participates in both primary nuclear export and re-export of tRNAs to the cytoplasm. In contrast, β-importin Msn5 preferentially assembles with RanGTP and spliced, aminoacylated tRNAs, documenting its role in tRNA nuclear re-export. Tef1/2 (the yeast form of translation elongation factor 1α [eEF1A]) aids the specificity of Msn5 for aminoacylated tRNAs to form a quaternary complex consisting of Msn5, RanGTP, aminoacylated tRNA, and Tef1/2. Assembly and/or stability of this quaternary complex requires Tef1/2, thereby facilitating efficient re-export of aminoacylated tRNAs to the cytoplasm.
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Affiliation(s)
- Hsiao-Yun Huang
- Department of Molecular Genetics, Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA
| | - Anita K Hopper
- Department of Molecular Genetics, Center for RNA Biology, The Ohio State University, Columbus, Ohio 43210, USA
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Khuperkar D, Helen M, Magre I, Joseph J. Inter-cellular transport of ran GTPase. PLoS One 2015; 10:e0125506. [PMID: 25894517 PMCID: PMC4403925 DOI: 10.1371/journal.pone.0125506] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2014] [Accepted: 03/24/2015] [Indexed: 12/25/2022] Open
Abstract
Ran, a member of the Ras-GTPase superfamily, has a well-established role in regulating the transport of macromolecules across the nuclear envelope (NE). Ran has also been implicated in mitosis, cell cycle progression, and NE formation. Over-expression of Ran is associated with various cancers, although the molecular mechanism underlying this phenomenon is unclear. Serendipitously, we found that Ran possesses the ability to move from cell-to-cell when transiently expressed in mammalian cells. Moreover, we show that the inter-cellular transport of Ran is GTP-dependent. Importantly, Ran displays a similar distribution pattern in the recipient cells as that in the donor cell and co-localizes with the Ran binding protein Nup358 (also called RanBP2). Interestingly, leptomycin B, an inhibitor of CRM1-mediated export, or siRNA mediated depletion of CRM1, significantly impaired the inter-cellular transport of Ran, suggesting a function for CRM1 in this process. These novel findings indicate a possible role for Ran beyond nucleo-cytoplasmic transport, with potential implications in inter-cellular communication and cancers.
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Affiliation(s)
| | - Mary Helen
- National Centre for Cell Science, Ganeshkhind, Pune, India
| | - Indrasen Magre
- National Centre for Cell Science, Ganeshkhind, Pune, India
| | - Jomon Joseph
- National Centre for Cell Science, Ganeshkhind, Pune, India
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Takano A, Kajita T, Mochizuki M, Endo T, Yoshihisa T. Cytosolic Hsp70 and co-chaperones constitute a novel system for tRNA import into the nucleus. eLife 2015; 4:e04659. [PMID: 25853343 PMCID: PMC4432389 DOI: 10.7554/elife.04659] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2014] [Accepted: 04/05/2015] [Indexed: 01/31/2023] Open
Abstract
tRNAs are unique among various RNAs in that they shuttle between the nucleus and the cytoplasm, and their localization is regulated by nutrient conditions. Although nuclear export of tRNAs has been well documented, the import machinery is poorly understood. Here, we identified Ssa2p, a major cytoplasmic Hsp70 in Saccharomyces cerevisiae, as a tRNA-binding protein whose deletion compromises nuclear accumulation of tRNAs upon nutrient starvation. Ssa2p recognizes several structural features of tRNAs through its nucleotide-binding domain, but prefers loosely-folded tRNAs, suggesting that Ssa2p has a chaperone-like activity for RNAs. Ssa2p also binds Nup116, one of the yeast nucleoporins. Sis1p and Ydj1p, cytoplasmic co-chaperones for Ssa proteins, were also found to contribute to the tRNA import. These results unveil a novel function of the Ssa2p system as a tRNA carrier for nuclear import by a novel mode of substrate recognition. Such Ssa2p-mediated tRNA import likely contributes to quality control of cytosolic tRNAs.
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Affiliation(s)
- Akira Takano
- Department of Chemistry, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Takuya Kajita
- Department of Chemistry, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Makoto Mochizuki
- Department of Chemistry, Graduate School of Science, Nagoya University, Nagoya, Japan
| | - Toshiya Endo
- Department of Chemistry, Graduate School of Science, Nagoya University, Nagoya, Japan
- Faculty of Life Sciences, Kyoto Sangyo University, Kyoto, Japan
| | - Tohru Yoshihisa
- Graduate School of Life Science, University of Hyogo, Kobe, Japan
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Quality Control Pathways for Nucleus-Encoded Eukaryotic tRNA Biosynthesis and Subcellular Trafficking. Mol Cell Biol 2015; 35:2052-8. [PMID: 25848089 DOI: 10.1128/mcb.00131-15] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
tRNAs perform an essential role in translating the genetic code. They are long-lived RNAs that are generated via numerous posttranscriptional steps. Eukaryotic cells have evolved numerous layers of quality control mechanisms to ensure that the tRNAs are appropriately structured, processed, and modified. We describe the known tRNA quality control processes that check tRNAs and correct or destroy aberrant tRNAs. These mechanisms employ two types of exonucleases, CCA end addition, tRNA nuclear aminoacylation, and tRNA subcellular traffic. We arrange these processes in order of the steps that occur from generation of precursor tRNAs by RNA polymerase (Pol) III transcription to end maturation and modification in the nucleus to splicing and additional modifications in the cytoplasm. Finally, we discuss the tRNA retrograde pathway, which allows tRNA reimport into the nucleus for degradation or repair.
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RNA Export through the NPC in Eukaryotes. Genes (Basel) 2015; 6:124-49. [PMID: 25802992 PMCID: PMC4377836 DOI: 10.3390/genes6010124] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Revised: 02/27/2015] [Accepted: 03/10/2015] [Indexed: 02/08/2023] Open
Abstract
In eukaryotic cells, RNAs are transcribed in the nucleus and exported to the cytoplasm through the nuclear pore complex. The RNA molecules that are exported from the nucleus into the cytoplasm include messenger RNAs (mRNAs), ribosomal RNAs (rRNAs), transfer RNAs (tRNAs), small nuclear RNAs (snRNAs), micro RNAs (miRNAs), and viral mRNAs. Each RNA is transported by a specific nuclear export receptor. It is believed that most of the mRNAs are exported by Nxf1 (Mex67 in yeast), whereas rRNAs, snRNAs, and a certain subset of mRNAs are exported in a Crm1/Xpo1-dependent manner. tRNAs and miRNAs are exported by Xpot and Xpo5. However, multiple export receptors are involved in the export of some RNAs, such as 60S ribosomal subunit. In addition to these export receptors, some adapter proteins are required to export RNAs. The RNA export system of eukaryotic cells is also used by several types of RNA virus that depend on the machineries of the host cell in the nucleus for replication of their genome, therefore this review describes the RNA export system of two representative viruses. We also discuss the NPC anchoring-dependent mRNA export factors that directly recruit specific genes to the NPC.
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Cautain B, Hill R, de Pedro N, Link W. Components and regulation of nuclear transport processes. FEBS J 2014; 282:445-62. [PMID: 25429850 PMCID: PMC7163960 DOI: 10.1111/febs.13163] [Citation(s) in RCA: 177] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Revised: 11/11/2014] [Accepted: 11/12/2014] [Indexed: 12/27/2022]
Abstract
The spatial separation of DNA replication and gene transcription in the nucleus and protein translation in the cytoplasm is a uniform principle of eukaryotic cells. This compartmentalization imposes a requirement for a transport network of macromolecules to shuttle these components in and out of the nucleus. This nucleo‐cytoplasmic transport of macromolecules is critical for both cell physiology and pathology. Consequently, investigating its regulation and disease‐associated alterations can reveal novel therapeutic approaches to fight human diseases, such as cancer or viral infection. The characterization of the nuclear pore complex, the identification of transport signals and transport receptors, as well as the characterization of the Ran system (providing the energy source for efficient cargo transport) has greatly facilitated our understanding of the components, mechanisms and regulation of the nucleo‐cytoplasmic transport of proteins in our cells. Here we review this knowledge with a specific emphasis on the selection of disease‐relevant molecular targets for potential therapeutic intervention.
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Affiliation(s)
- Bastien Cautain
- Fundacion MEDINA Parque tecnológico ciencias de la salud, Granada, Spain
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Fung HYJ, Chook YM. Atomic basis of CRM1-cargo recognition, release and inhibition. Semin Cancer Biol 2014; 27:52-61. [PMID: 24631835 PMCID: PMC4108548 DOI: 10.1016/j.semcancer.2014.03.002] [Citation(s) in RCA: 106] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2014] [Accepted: 03/01/2014] [Indexed: 11/19/2022]
Abstract
CRM1 or XPO1 is the major nuclear export receptor in the cell, which controls the nuclear-cytoplasmic localization of many proteins and RNAs. CRM1 is also a promising cancer drug target as the transport receptor is overexpressed in many cancers where some of its cargos are misregulated and mislocalized to the cytoplasm. Atomic level understanding of CRM1 function has greatly facilitated recent drug discovery and development of CRM1 inhibitors to target a variety of malignancies. Numerous atomic resolution CRM1 structures are now available, explaining how the exporter recognizes nuclear export signals in its cargos, how RanGTP and cargo bind with positive cooperativity, how RanBP1 causes release of export cargos in the cytoplasm and how diverse inhibitors such as Leptomycin B and the new KPT-SINE compounds block nuclear export. This review summarizes structure-function studies that explain CRM1-cargo recognition, release and inhibition.
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Affiliation(s)
- Ho Yee Joyce Fung
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, 6001 Forest Park, Dallas, TX 75390-9041, USA.
| | - Yuh Min Chook
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, 6001 Forest Park, Dallas, TX 75390-9041, USA.
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Huang HY, Hopper AK. Separate responses of karyopherins to glucose and amino acid availability regulate nucleocytoplasmic transport. Mol Biol Cell 2014; 25:2840-52. [PMID: 25057022 PMCID: PMC4161518 DOI: 10.1091/mbc.e14-04-0948] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The subcellular distribution of yeast β-importins inverts upon acute glucose deprivation, likely due to collapse of the RanGTP nuclear–cytoplasmic gradient. This redistribution of β-importins likely results in rapid widespread alterations of the traffic of macromolecules between the nucleus and cytoplasm in response to glucose limitation. The importin-β family members (karyopherins) mediate the majority of nucleocytoplasmic transport. Msn5 and Los1, members of the importin-β family, function in tRNA nuclear export. tRNAs move bidirectionally between the nucleus and the cytoplasm. Nuclear tRNA accumulation occurs upon amino acid (aa) or glucose deprivation. To understand the mechanisms regulating tRNA subcellular trafficking, we investigated whether Msn5 and Los1 are regulated in response to nutrient availability. We provide evidence that tRNA subcellular trafficking is regulated by distinct aa-sensitive and glucose-sensitive mechanisms. Subcellular distributions of Msn5 and Los1 are altered upon glucose deprivation but not aa deprivation. Redistribution of tRNA exportins from the nucleus to the cytoplasm likely provides one mechanism for tRNA nuclear distribution upon glucose deprivation. We extended our studies to other members of the importin-β family and found that all tested karyopherins invert their subcellular distributions upon glucose deprivation but not aa deprivation. Glucose availability regulates the subcellular distributions of karyopherins likely due to alteration of the RanGTP gradient since glucose deprivation causes redistribution of Ran. Thus nuclear–cytoplasmic distribution of macromolecules is likely generally altered upon glucose deprivation due to collapse of the RanGTP gradient and redistribution of karyopherins between the nucleus and the cytoplasm.
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Affiliation(s)
- Hsiao-Yun Huang
- Department of Molecular Genetics and Center for RNA Biology, Ohio State University, Columbus, OH 43210 Graduate Program in Molecular, Cellular, and Developmental Biology, Ohio State University, Columbus, OH 43210
| | - Anita K Hopper
- Department of Molecular Genetics and Center for RNA Biology, Ohio State University, Columbus, OH 43210
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Soma A. Circularly permuted tRNA genes: their expression and implications for their physiological relevance and development. Front Genet 2014; 5:63. [PMID: 24744771 PMCID: PMC3978253 DOI: 10.3389/fgene.2014.00063] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 03/12/2014] [Indexed: 12/02/2022] Open
Abstract
A number of genome analyses and searches using programs that focus on the RNA-specific bulge-helix-bulge (BHB) motif have uncovered a wide variety of disrupted tRNA genes. The results of these analyses have shown that genetic information encoding functional RNAs is described in the genome cryptically and is retrieved using various strategies. One such strategy is represented by circularly permuted tRNA genes, in which the sequences encoding the 5′-half and 3′-half of the specific tRNA are separated and inverted on the genome. Biochemical analyses have defined a processing pathway in which the termini of tRNA precursors (pre-tRNAs) are ligated to form a characteristic circular RNA intermediate, which is then cleaved at the acceptor-stem to generate the typical cloverleaf structure with functional termini. The sequences adjacent to the processing site located between the 3′-half and the 5′-half of pre-tRNAs potentially form a BHB motif, which is the dominant recognition site for the tRNA-intron splicing endonuclease, suggesting that circularization of pre-tRNAs depends on the splicing machinery. Some permuted tRNAs contain a BHB-mediated intron in their 5′- or 3′-half, meaning that removal of an intron, as well as swapping of the 5′- and 3′-halves, are required during maturation of their pre-tRNAs. To date, 34 permuted tRNA genes have been identified from six species of unicellular algae and one archaeon. Although their physiological significance and mechanism of development remain unclear, the splicing system of BHB motifs seems to have played a key role in the formation of permuted tRNA genes. In this review, current knowledge of circularly permuted tRNA genes is presented and some unanswered questions regarding these species are discussed.
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Affiliation(s)
- Akiko Soma
- Graduate School of Horticulture, Chiba University Matsudo, Japan
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Retrograde transfer RNA nuclear import provides a new level of tRNA quality control in Saccharomyces cerevisiae. Proc Natl Acad Sci U S A 2013; 110:21042-7. [PMID: 24297920 DOI: 10.1073/pnas.1316579110] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In eukaryotes, transfer RNAs (tRNAs) are transcribed in the nucleus yet function in the cytoplasm; thus, tRNA movement within the cell was believed to be unidirectional--from the nucleus to the cytoplasm. It is now known that mature tRNAs also move in a retrograde direction from the cytoplasm to the nucleus via retrograde tRNA nuclear import, a process that is conserved from yeast to vertebrates. The biological significance of this tRNA nuclear import is not entirely clear. We hypothesized that retrograde tRNA nuclear import might function in proofreading tRNAs to ensure that only proper tRNAs reside in the cytoplasm and interact with the translational machinery. Here we identify two major types of aberrant tRNAs in yeast: a 5', 3' end-extended, spliced tRNA and hypomodified tRNAs. We show that both types of aberrant tRNAs accumulate in mutant cells that are defective in tRNA nuclear traffic, suggesting that they are normally imported into the nucleus and are repaired or degraded. The retrograde pathway functions in parallel with the cytoplasmic rapid tRNA decay pathway previously demonstrated to monitor tRNA quality, and cells are not viable if they lack both pathways. Our data support the hypothesis that the retrograde process provides a newly discovered level of tRNA quality control as a pathway that monitors both end processing of pre-tRNAs and the modification state of mature tRNAs.
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Transfer RNA post-transcriptional processing, turnover, and subcellular dynamics in the yeast Saccharomyces cerevisiae. Genetics 2013; 194:43-67. [PMID: 23633143 DOI: 10.1534/genetics.112.147470] [Citation(s) in RCA: 145] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Transfer RNAs (tRNAs) are essential for protein synthesis. In eukaryotes, tRNA biosynthesis employs a specialized RNA polymerase that generates initial transcripts that must be subsequently altered via a multitude of post-transcriptional steps before the tRNAs beome mature molecules that function in protein synthesis. Genetic, genomic, biochemical, and cell biological approaches possible in the powerful Saccharomyces cerevisiae system have led to exciting advances in our understandings of tRNA post-transcriptional processing as well as to novel insights into tRNA turnover and tRNA subcellular dynamics. tRNA processing steps include removal of transcribed leader and trailer sequences, addition of CCA to the 3' mature sequence and, for tRNA(His), addition of a 5' G. About 20% of yeast tRNAs are encoded by intron-containing genes. The three-step splicing process to remove the introns surprisingly occurs in the cytoplasm in yeast and each of the splicing enzymes appears to moonlight in functions in addition to tRNA splicing. There are 25 different nucleoside modifications that are added post-transcriptionally, creating tRNAs in which ∼15% of the residues are nucleosides other than A, G, U, or C. These modified nucleosides serve numerous important functions including tRNA discrimination, translation fidelity, and tRNA quality control. Mature tRNAs are very stable, but nevertheless yeast cells possess multiple pathways to degrade inappropriately processed or folded tRNAs. Mature tRNAs are also dynamic in cells, moving from the cytoplasm to the nucleus and back again to the cytoplasm; the mechanism and function of this retrograde process is poorly understood. Here, the state of knowledge for tRNA post-transcriptional processing, turnover, and subcellular dynamics is addressed, highlighting the questions that remain.
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Characterization of export receptor exportins (XPOs) in the parasite Schistosoma mansoni. Parasitol Res 2013; 112:4151-9. [PMID: 24013345 DOI: 10.1007/s00436-013-3606-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Accepted: 08/28/2013] [Indexed: 10/26/2022]
Abstract
Several proteins and different species of RNA that are produced in the nucleus are exported through the nuclear pore complexes, which require a family of conserved nuclear export receptors called exportins (XPOs). It has been reported that the XPOs (XPO1, XPO5, and XPOT) are directly involved in the transport processes of noncoding RNAs from the nucleus to the cytoplasm and/or from cytoplasm to the nucleus. All three genes are present in fungi, plants, and deuterostome metazoans. However, protostome metazoan species lack one of the three genes across evolution. In this report, we have demonstrated that all three XPO proteins are present in the parasite protostome Schistosoma mansoni. As this parasite has a complex life cycle presenting several stages in different hosts and environments, implying a differential gene regulation, we proposed a genomic analysis of XPOs to validate their annotation. The results showed the conservation of exportin family members and gene duplication events in S. mansoni. We performed quantitative RT-PCR, which revealed an upregulation of SmXPO1 in 24 h schistosomula (sixfold when compared with cercariae), and similar transcription levels were observed for SmXPO5 and SmXPOT in all the analyzed stages. These three XPO proteins have been identified for the first time in the protostome clade, which suggests a higher complexity in RNA transport in the parasite S. mansoni. Taken together, these results suggest that RNA transport by exportins might control cellular processes during cercariae, schistosomula, and adult worm development.
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