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Makio T, Zhang K, Love N, Mast FD, Liu X, Elaish M, Hobman T, Aitchison JD, Fontoura BMA, Wozniak RW. SARS-CoV-2 Orf6 is positioned in the nuclear pore complex by Rae1 to inhibit nucleocytoplasmic transport. Mol Biol Cell 2024; 35:ar62. [PMID: 38507240 PMCID: PMC11151100 DOI: 10.1091/mbc.e23-10-0386] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2023] [Revised: 03/07/2024] [Accepted: 03/15/2024] [Indexed: 03/22/2024] Open
Abstract
The Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) accessory protein Orf6 works as an interferon antagonist, in part, by inhibiting the nuclear import activated p-STAT1, an activator of interferon-stimulated genes, and the export of the poly(A) RNA. Insight into the transport regulatory function of Orf6 has come from the observation that Orf6 binds to the nuclear pore complex (NPC) components: Rae1 and Nup98. To gain further insight into the mechanism of Orf6-mediated transport inhibition, we examined the role of Rae1 and Nup98. We show that Rae1 alone is not necessary to support p-STAT1 import or nuclear export of poly(A) RNA. Moreover, the loss of Rae1 suppresses the transport inhibitory activity of Orf6. We propose that the Rae1/Nup98 complex strategically positions Orf6 within the NPC where it alters FG-Nup interactions and their ability to support nuclear transport. In addition, we show that Rae1 is required for normal viral protein production during SARS-CoV-2 infection presumably through its role in supporting Orf6 function.
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Affiliation(s)
- Tadashi Makio
- Department of Cell Biology and Li Ka Shing Institute of Virology, University of Alberta, Edmonton, AB, Canada T6G 2H7
| | - Ke Zhang
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75235
- Shanghai Institute of Immunity and Infection, Chinese Academy of Sciences, Shanghai 200031, China
| | - Nicole Love
- Department of Cell Biology and Li Ka Shing Institute of Virology, University of Alberta, Edmonton, AB, Canada T6G 2H7
| | - Fred D. Mast
- Center for Global Infectious Disease Research, Seattle Children's Research Institute, Seattle, WA 98101
| | - Xue Liu
- Shanghai Institute of Immunity and Infection, Chinese Academy of Sciences, Shanghai 200031, China
| | - Mohamed Elaish
- Department of Cell Biology and Li Ka Shing Institute of Virology, University of Alberta, Edmonton, AB, Canada T6G 2H7
| | - Tom Hobman
- Department of Cell Biology and Li Ka Shing Institute of Virology, University of Alberta, Edmonton, AB, Canada T6G 2H7
| | - John D. Aitchison
- Center for Global Infectious Disease Research, Seattle Children's Research Institute, Seattle, WA 98101
- Department of Pediatrics, University of Washington, Seattle, WA 98195
- Department of Biochemistry, University of Washington, Seattle, WA 98195
| | - Beatriz M. A. Fontoura
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75235
| | - Richard W. Wozniak
- Department of Cell Biology and Li Ka Shing Institute of Virology, University of Alberta, Edmonton, AB, Canada T6G 2H7
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Qiu Y, Sun Y, Zheng X, Gong L, Yang L, Xiang B. Identification of host proteins interacting with the E protein of porcine epidemic diarrhea virus. Front Microbiol 2024; 15:1380578. [PMID: 38577683 PMCID: PMC10994376 DOI: 10.3389/fmicb.2024.1380578] [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: 02/01/2024] [Accepted: 02/29/2024] [Indexed: 04/06/2024] Open
Abstract
Introduction Porcine epidemic diarrhea (PED) is an acute, highly contagious, and high-mortality enterophilic infectious disease caused by the porcine epidemic diarrhea virus (PEDV). PEDV is globally endemic and causes substantial economic losses in the swine industry. The PEDV E protein is the smallest structural protein with high expression levels that interacts with the M protein and participates in virus assembly. However, how the host proteins interact with E proteins in PEDV replication remains unknown. Methods We identified host proteins that interact with the PEDV E protein using a combination of PEDV E protein-labeled antibody co-immunoprecipitation and tandem liquid-chromatography mass-spectroscopy (LC-MS/MS). Results Bioinformatical analysis showed that in eukaryotes, ribosome biogenesis, RNA transport, and amino acid biosynthesis represent the three main pathways that are associated with the E protein. The interaction between the E protein and isocitrate dehydrogenase [NAD] β-subunit (NAD-IDH-β), DNA-directed RNA polymerase II subunit RPB9, and mRNA-associated protein MRNP 41 was validated using co-immunoprecipitation and confocal assays. NAD-IDH-β overexpression significantly inhibited viral replication. Discussion The antiviral effect of NAD-IDH-β suggesting that the E protein may regulate host metabolism by interacting with NAD-IDH-β, thereby reducing the available energy for viral replication. Elucidating the interaction between the PEDV E protein and host proteins may clarify its role in viral replication. These results provide a theoretical basis for the study of PEDV infection mechanism and antiviral targets.
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Affiliation(s)
- Yingwu Qiu
- College of Veterinary Medicine, Yunnan Agricultural University, Kunming, China
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China
| | - Yingshuo Sun
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China
| | - Xiaoyu Zheng
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China
| | - Lang Gong
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China
| | - Liangyu Yang
- College of Veterinary Medicine, Yunnan Agricultural University, Kunming, China
| | - Bin Xiang
- College of Veterinary Medicine, Yunnan Agricultural University, Kunming, China
- College of Veterinary Medicine, South China Agricultural University, Guangzhou, China
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3
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Guo J, Zhu Y, Ma X, Shang G, Liu B, Zhang K. Virus Infection and mRNA Nuclear Export. Int J Mol Sci 2023; 24:12593. [PMID: 37628773 PMCID: PMC10454920 DOI: 10.3390/ijms241612593] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2023] [Revised: 07/29/2023] [Accepted: 08/03/2023] [Indexed: 08/27/2023] Open
Abstract
Gene expression in eukaryotes begins with transcription in the nucleus, followed by the synthesis of messenger RNA (mRNA), which is then exported to the cytoplasm for its translation into proteins. Along with transcription and translation, mRNA export through the nuclear pore complex (NPC) is an essential regulatory step in eukaryotic gene expression. Multiple factors regulate mRNA export and hence gene expression. Interestingly, proteins from certain types of viruses interact with these factors in infected cells, and such an interaction interferes with the mRNA export of the host cell in favor of viral RNA export. Thus, these viruses hijack the host mRNA nuclear export mechanism, leading to a reduction in host gene expression and the downregulation of immune/antiviral responses. On the other hand, the viral mRNAs successfully evade the host surveillance system and are efficiently exported from the nucleus to the cytoplasm for translation, which enables the continuation of the virus life cycle. Here, we present this review to summarize the mechanisms by which viruses suppress host mRNA nuclear export during infection, as well as the key strategies that viruses use to facilitate their mRNA nuclear export. These studies have revealed new potential antivirals that may be used to inhibit viral mRNA transport and enhance host mRNA nuclear export, thereby promoting host gene expression and immune responses.
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Affiliation(s)
- Jiayin Guo
- University of Chinese Academy of Sciences, Beijing 100049, China; (J.G.); (Y.Z.); (X.M.)
| | - Yaru Zhu
- University of Chinese Academy of Sciences, Beijing 100049, China; (J.G.); (Y.Z.); (X.M.)
| | - Xiaoya Ma
- University of Chinese Academy of Sciences, Beijing 100049, China; (J.G.); (Y.Z.); (X.M.)
| | - Guijun Shang
- Shanxi Provincial Key Laboratory of Protein Structure Determination, Shanxi Academy of Advanced Research and Innovation, Taiyuan 030012, China;
| | - Bo Liu
- Key Laboratory of Molecular Virology and Immunology, Chinese Academy of Sciences, Shanghai 200031, China
- Shanghai Huashen Institute of Microbes and Infections, Shanghai 200052, China
| | - Ke Zhang
- Key Laboratory of Molecular Virology and Immunology, Chinese Academy of Sciences, Shanghai 200031, China
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4
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Tang Z, Luo W, Huang Z, Yuan M, Wu W, Yang K. Spodoptera frugiperda mRNA export factor interacts with and mediates the nuclear import of Autographa californica multiple nucleopolyhedrovirus ORF34 (Ac34). Virus Res 2021; 299:198438. [PMID: 33901592 DOI: 10.1016/j.virusres.2021.198438] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2021] [Revised: 04/16/2021] [Accepted: 04/20/2021] [Indexed: 01/01/2023]
Abstract
Autographa californica multiple nucleopolyhedrovirus orf34 (ac34) is one of the unique genes of alphabaculoviruses. For successful alphabaculovirus replication, viral proteins must be transported to the nucleus. Our previous study showed that the nuclear localization of Ac34 was required for optimal production of budded virions. To investigate the mechanism of Ac34 nuclear import, mass spectrometric analysis was performed to identify potential proteins that may be involved in the nuclear import of Ac34. The result indicated that Spodoptera frugiperda mRNA export factor (SfMEF) may interact with Ac34 during baculovirus infection. Co-immunoprecipitation assays confirmed that Ac34 could interact with SfMEF in the absence of other baculovirus proteins. The deletion of ac34 did not affect the subcellular localization of SfMEF; however, knocking down Sfmef prevented the nuclear import of Ac34 in virus-infected cells. The mutations of C116 or C119 in a potential CCCH zinc finger motif (C116-X2-C119-X8-C128-X2-H131) of Ac34 led to an exclusive cytoplasmic distribution of Ac34, in consistent with our previous finding of mutations of C128 or H131 in this motif. Co-immunoprecipitation analysis showed that the above mutations in the potential zinc finger motif disrupted the interaction between Ac34 and SfMEF, and the loss of the interaction resulted in decreased BV production. Our findings demonstrated that SfMEF interacts with and mediates the nuclear import of Ac34, which is a new nucleocytoplasmic transport pathway used by alphabaculovirus to achieve successful viral replication within the nucleus of the infected cells.
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Affiliation(s)
- Zhimin Tang
- State Key Lab of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China
| | - Wangtai Luo
- State Key Lab of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China
| | - Zhihong Huang
- State Key Lab of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China
| | - Meijin Yuan
- State Key Lab of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China
| | - Wenbi Wu
- State Key Lab of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China.
| | - Kai Yang
- State Key Lab of Biocontrol, School of Life Sciences, Sun Yat-sen University, Guangzhou, 510275, China
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5
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Pardamean CI, Wu TT. Inhibition of Host Gene Expression by KSHV: Sabotaging mRNA Stability and Nuclear Export. Front Cell Infect Microbiol 2021; 11:648055. [PMID: 33898329 PMCID: PMC8062738 DOI: 10.3389/fcimb.2021.648055] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Accepted: 03/19/2021] [Indexed: 12/25/2022] Open
Abstract
Viruses are known for their ability to alter host gene expression. Kaposi sarcoma-associated herpesvirus has two proteins that obstruct host gene expression. KSHV SOX, encoded by the open reading frame 37 (ORF37), induces a widespread cytoplasmic mRNA degradation and a block on mRNA nuclear export. The other KSHV protein, encoded by the open reading frame 10 (ORF10), was recently identified to inhibit host gene expression through its direct function on the cellular mRNA export pathway. In this review, we summarize the studies on both SOX and ORF10 in efforts to elucidate their mechanisms. We also discuss how the findings based on a closely related rodent virus, murine gammaherpesvirus-68 (MHV-68), complement the KSHV findings to decipher the role of these two proteins in viral pathogenesis.
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Affiliation(s)
- Carissa Ikka Pardamean
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA, United States
| | - Ting-Ting Wu
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, CA, United States
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6
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Kato K, Ikliptikawati DK, Kobayashi A, Kondo H, Lim K, Hazawa M, Wong RW. Overexpression of SARS-CoV-2 protein ORF6 dislocates RAE1 and NUP98 from the nuclear pore complex. Biochem Biophys Res Commun 2020; 536:59-66. [PMID: 33360543 PMCID: PMC7733692 DOI: 10.1016/j.bbrc.2020.11.115] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Accepted: 11/29/2020] [Indexed: 12/27/2022]
Abstract
The novel human betacoronavirus SARS-CoV-2 has caused an unprecedented pandemic in the 21st century. Several studies have revealed interactions between SARS-CoV-2 viral proteins and host nucleoporins, yet their functions are largely unknown. Here, we demonstrate that the open-reading frame 6 (ORF6) of SARS-CoV-2 can directly manipulate localization and functions of nucleoporins. We found that ORF6 protein disrupted nuclear rim staining of nucleoporins RAE1 and NUP98. Consequently, this disruption caused aberrant nucleocytoplasmic trafficking and led to nuclear accumulation of mRNA transporters such as hnRNPA1. Ultimately, host cell nucleus size was reduced and cell growth was halted.
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Affiliation(s)
- Koki Kato
- School of Natural System, College of Science and Engineering, Kanazawa University, Kanazawa, Ishikawa, 920-1192, Japan
| | - Dini Kurnia Ikliptikawati
- School of Natural System, College of Science and Engineering, Kanazawa University, Kanazawa, Ishikawa, 920-1192, Japan
| | - Akiko Kobayashi
- Cell-Bionomics Research Unit, Institute for Frontier Science Initiative (INFINITI), Kanazawa University, Kanazawa, Ishikawa, 920-1192, Japan.
| | - Hiroya Kondo
- Division of Transdisciplinary Sciences, Graduate School of Frontier Science Initiative, Kanazawa University, Kanazawa, Ishikawa, 920-1192, Japan
| | - Keesiang Lim
- WPI-Nano Life Science Institute, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa, 920-1192, Japan
| | - Masaharu Hazawa
- School of Natural System, College of Science and Engineering, Kanazawa University, Kanazawa, Ishikawa, 920-1192, Japan; Cell-Bionomics Research Unit, Institute for Frontier Science Initiative (INFINITI), Kanazawa University, Kanazawa, Ishikawa, 920-1192, Japan; Division of Transdisciplinary Sciences, Graduate School of Frontier Science Initiative, Kanazawa University, Kanazawa, Ishikawa, 920-1192, Japan; WPI-Nano Life Science Institute, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa, 920-1192, Japan
| | - Richard W Wong
- School of Natural System, College of Science and Engineering, Kanazawa University, Kanazawa, Ishikawa, 920-1192, Japan; Cell-Bionomics Research Unit, Institute for Frontier Science Initiative (INFINITI), Kanazawa University, Kanazawa, Ishikawa, 920-1192, Japan; Division of Transdisciplinary Sciences, Graduate School of Frontier Science Initiative, Kanazawa University, Kanazawa, Ishikawa, 920-1192, Japan; WPI-Nano Life Science Institute, Kanazawa University, Kakuma-machi, Kanazawa, Ishikawa, 920-1192, Japan.
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7
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Xie Y, Ren Y. Mechanisms of nuclear mRNA export: A structural perspective. Traffic 2019; 20:829-840. [PMID: 31513326 DOI: 10.1111/tra.12691] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Accepted: 08/26/2019] [Indexed: 12/28/2022]
Abstract
Export of mRNA from the nucleus to the cytoplasm is a critical process for all eukaryotic gene expression. As mRNA is synthesized, it is packaged with a myriad of RNA-binding proteins to form ribonucleoprotein particles (mRNPs). For each step in the processes of maturation and export, mRNPs must have the correct complement of proteins. Much of the mRNA export pathway revolves around the heterodimeric export receptor yeast Mex67•Mtr2/human NXF1•NXT1, which is recruited to signal the completion of nuclear mRNP assembly, mediates mRNP targeting/translocation through the nuclear pore complex (NPC), and is displaced at the cytoplasmic side of the NPC to release the mRNP into the cytoplasm. Directionality of the transport is governed by at least two DEAD-box ATPases, yeast Sub2/human UAP56 in the nucleus and yeast Dbp5/human DDX19 at the cytoplasmic side of the NPC, which respectively mediate the association and dissociation of Mex67•Mtr2/NXF1•NXT1 onto the mRNP. Here we review recent progress from structural studies of key constituents in different steps of nuclear mRNA export. These findings have laid the foundation for further studies to obtain a comprehensive mechanistic view of the mRNA export pathway.
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Affiliation(s)
- Yihu Xie
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee
| | - Yi Ren
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee
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8
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Stockum A, Snijders AP, Maertens GN. USP11 deubiquitinates RAE1 and plays a key role in bipolar spindle formation. PLoS One 2018; 13:e0190513. [PMID: 29293652 PMCID: PMC5749825 DOI: 10.1371/journal.pone.0190513] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 12/15/2017] [Indexed: 11/26/2022] Open
Abstract
Correct segregation of the mitotic chromosomes into daughter cells is a highly regulated process critical to safeguard genome stability. During M phase the spindle assembly checkpoint (SAC) ensures that all kinetochores are correctly attached before its inactivation allows progression into anaphase. Upon SAC inactivation, the anaphase promoting complex/cyclosome (APC/C) E3 ligase ubiquitinates and targets cyclin B and securin for proteasomal degradation. Here, we describe the identification of Ribonucleic Acid Export protein 1 (RAE1), a protein previously shown to be involved in SAC regulation and bipolar spindle formation, as a novel substrate of the deubiquitinating enzyme (DUB) Ubiquitin Specific Protease 11 (USP11). Lentiviral knock-down of USP11 or RAE1 in U2OS cells drastically reduces cell proliferation and increases multipolar spindle formation. We show that USP11 is associated with the mitotic spindle, does not regulate SAC inactivation, but controls ubiquitination of RAE1 at the mitotic spindle, hereby functionally modulating its interaction with Nuclear Mitotic Apparatus protein (NuMA).
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Affiliation(s)
- Anna Stockum
- Imperial College London, Department of Medicine, Division of Infectious Diseases, Norfolk Place, London, United Kingdom
| | - Ambrosius P. Snijders
- Francis Crick Institute, The Crick Mass Spectrometry Science Technology Platform, 1 Midland Road, London, United Kingdom
| | - Goedele N. Maertens
- Imperial College London, Department of Medicine, Division of Infectious Diseases, Norfolk Place, London, United Kingdom
- * E-mail:
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9
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Li D, Zhang L, Li X, Kong X, Wang X, Li Y, Liu Z, Wang J, Li X, Yang Y. AtRAE1 is involved in degradation of ABA receptor RCAR1 and negatively regulates ABA signalling in Arabidopsis. PLANT, CELL & ENVIRONMENT 2018; 41:231-244. [PMID: 29044697 DOI: 10.1111/pce.13086] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 09/24/2017] [Accepted: 09/28/2017] [Indexed: 06/07/2023]
Abstract
The phytohormone abscisic acid (ABA) plays an important role in regulating plant growth, development, and adaption to various environmental stresses. Regulatory components of ABA receptors (RCARs, also known as PYR/PYLs) sense ABA and initiate ABA signalling through inhibiting the activities of protein phosphatase 2C in Arabidopsis. However, the way in which ABA receptors are regulated is not well known. A DWD protein AtRAE1 (for RNA export factor 1 in Arabidopsis), which may act as a substrate receptor of CUL4-DDB1 E3 ligase, is an interacting partner of RCAR1/PYL9. The physical interaction between RCAR1 and AtRAE1 is confirmed in vitro and in vivo. Overexpression of AtRAE1 in Arabidopsis causes reduced sensitivity of plants to ABA, whereas suppression of AtRAE1 causes increased sensitivity to ABA. Analysis of protein stability demonstrates that RCAR1 is ubiquitinated and degraded in plant cells and AtRAE1 regulates the degradation speed of RCAR1. Our findings indicate that AtRAE1 likely participates in ABA signalling through regulating the degradation of ABA receptor RCAR1.
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Affiliation(s)
- Dekuan Li
- Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, China
| | - Liang Zhang
- Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, China
| | - Xiaoyi Li
- Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, China
| | - Xiangge Kong
- Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, China
| | - Xiaoyu Wang
- Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, China
| | - Ying Li
- Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, China
| | - Zhibin Liu
- Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, China
| | - Jianmei Wang
- Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, China
| | - Xufeng Li
- Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, China
| | - Yi Yang
- Key Laboratory of Bio-Resources and Eco-Environment of Ministry of Education, College of Life Sciences, Sichuan University, Chengdu, 610065, China
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10
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Gong D, Kim YH, Xiao Y, Du Y, Xie Y, Lee KK, Feng J, Farhat N, Zhao D, Shu S, Dai X, Chanda SK, Rana TM, Krogan NJ, Sun R, Wu TT. A Herpesvirus Protein Selectively Inhibits Cellular mRNA Nuclear Export. Cell Host Microbe 2017; 20:642-653. [PMID: 27832591 DOI: 10.1016/j.chom.2016.10.004] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Revised: 09/06/2016] [Accepted: 10/05/2016] [Indexed: 11/19/2022]
Abstract
Nuclear mRNA export is highly regulated to ensure accurate cellular gene expression. Viral inhibition of cellular mRNA export can enhance viral access to the cellular translation machinery and prevent anti-viral protein production but is generally thought to be nonselective. We report that ORF10 of Kaposi's sarcoma-associated herpesvirus (KSHV), a nuclear DNA virus, inhibits mRNA export in a transcript-selective manner to control cellular gene expression. Nuclear export inhibition by ORF10 requires an interaction with an RNA export factor, Rae1. Genome-wide analysis reveals a subset of cellular mRNAs whose nuclear export is blocked by ORF10 with the 3' UTRs of ORF10-targeted transcripts conferring sensitivity to export inhibition. The ORF10-Rae1 interaction is important for the virus to express viral genes and produce infectious virions. These results suggest that a nuclear DNA virus can selectively interfere with RNA export to restrict host gene expression for optimal replication.
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Affiliation(s)
- Danyang Gong
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Yong Hoon Kim
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Yuchen Xiao
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Yushen Du
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Yafang Xie
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Kevin K Lee
- School of Dentistry, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Jun Feng
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Nisar Farhat
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Dawei Zhao
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Sara Shu
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Xinghong Dai
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Sumit K Chanda
- Infectious and Inflammatory Disease Center, Sanford-Burnham Medical Research Institute, La Jolla, CA 92037, USA
| | - Tariq M Rana
- Department of Pediatrics, University of California, San Diego, La Jolla, CA 92093, USA
| | - Nevan J Krogan
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, San Francisco, CA 94158, USA
| | - Ren Sun
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Ting-Ting Wu
- Department of Molecular and Medical Pharmacology, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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11
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Satoh R, Matsumura Y, Tanaka A, Takada M, Ito Y, Hagihara K, Inari M, Kita A, Fukao A, Fujiwara T, Hirai S, Tani T, Sugiura R. Spatial regulation of the KH domain RNA-binding protein Rnc1 mediated by a Crm1-independent nuclear export system in Schizosaccharomyces pombe. Mol Microbiol 2017; 104:428-448. [PMID: 28142187 DOI: 10.1111/mmi.13636] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/26/2017] [Indexed: 10/20/2022]
Abstract
RNA-binding proteins (RBPs) play important roles in the posttranscriptional regulation of gene expression, including mRNA stability, transport and translation. Fission yeast rnc1+ encodes a K Homology (KH)-type RBP, which binds and stabilizes the Pmp1 MAPK phosphatase mRNA thereby suppressing the Cl- hypersensitivity of calcineurin deletion and MAPK signaling mutants. Here, we analyzed the spatial regulation of Rnc1 and discovered a putative nuclear export signal (NES)Rnc1 , which dictates the cytoplasmic localization of Rnc1 in a Crm1-independent manner. Notably, mutations in the NESRnc1 altered nucleocytoplasmic distribution of Rnc1 and abolished its function to suppress calcineurin deletion, although the Rnc1 NES mutant maintains the ability to bind Pmp1 mRNA. Intriguingly, the Rnc1 NES mutant destabilized Pmp1 mRNA, suggesting the functional importance of the Rnc1 cytoplasmic localization. Mutation in Rae1, but not Mex67 deletion or overproduction, induced Rnc1 accumulation in the nucleus, suggesting that Rnc1 is exported from the nucleus to the cytoplasm via the mRNA export pathway involving Rae1. Importantly, mutations in the Rnc1 KH-domains abolished the mRNA-binding ability and induced nuclear localization, suggesting that Rnc1 may be exported from the nucleus together with its target mRNAs. Collectively, the functional Rae1-dependent mRNA export system may influence the cytoplasmic localization and function of Rnc1.
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Affiliation(s)
- Ryosuke Satoh
- Laboratory of Molecular Pharmacogenomics, Department of Pharmaceutical Sciences, Kindai University, Higashiosaka City, Osaka, 577-8502, Japan
| | - Yasuhiro Matsumura
- Laboratory of Molecular Pharmacogenomics, Department of Pharmaceutical Sciences, Kindai University, Higashiosaka City, Osaka, 577-8502, Japan
| | - Akitomo Tanaka
- Laboratory of Molecular Pharmacogenomics, Department of Pharmaceutical Sciences, Kindai University, Higashiosaka City, Osaka, 577-8502, Japan
| | - Makoto Takada
- Laboratory of Molecular Pharmacogenomics, Department of Pharmaceutical Sciences, Kindai University, Higashiosaka City, Osaka, 577-8502, Japan
| | - Yuna Ito
- Laboratory of Molecular Pharmacogenomics, Department of Pharmaceutical Sciences, Kindai University, Higashiosaka City, Osaka, 577-8502, Japan
| | - Kanako Hagihara
- Laboratory of Molecular Pharmacogenomics, Department of Pharmaceutical Sciences, Kindai University, Higashiosaka City, Osaka, 577-8502, Japan
| | - Masahiro Inari
- Laboratory of Molecular Pharmacogenomics, Department of Pharmaceutical Sciences, Kindai University, Higashiosaka City, Osaka, 577-8502, Japan
| | - Ayako Kita
- Laboratory of Molecular Pharmacogenomics, Department of Pharmaceutical Sciences, Kindai University, Higashiosaka City, Osaka, 577-8502, Japan
| | - Akira Fukao
- Laboratory of Biochemistry, Department of Pharmacy, Kindai University, Higashiosaka City, Osaka, 577-8502, Japan
| | - Toshinobu Fujiwara
- Laboratory of Biochemistry, Department of Pharmacy, Kindai University, Higashiosaka City, Osaka, 577-8502, Japan
| | - Shinya Hirai
- Department of Biological Sciences Graduate School of Science and Technology, Kumamoto University, Kumamoto, Kumamoto, 860-8555, Japan
| | - Tokio Tani
- Department of Biological Sciences Graduate School of Science and Technology, Kumamoto University, Kumamoto, Kumamoto, 860-8555, Japan
| | - Reiko Sugiura
- Laboratory of Molecular Pharmacogenomics, Department of Pharmaceutical Sciences, Kindai University, Higashiosaka City, Osaka, 577-8502, Japan
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12
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Bonnet A, Palancade B. Regulation of mRNA trafficking by nuclear pore complexes. Genes (Basel) 2014; 5:767-91. [PMID: 25184662 PMCID: PMC4198930 DOI: 10.3390/genes5030767] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 08/25/2014] [Accepted: 08/26/2014] [Indexed: 11/17/2022] Open
Abstract
Over the last two decades, multiple studies have explored the mechanisms governing mRNA export out of the nucleus, a crucial step in eukaryotic gene expression. During transcription and processing, mRNAs are assembled into messenger ribonucleoparticles (mRNPs). mRNPs are then exported through nuclear pore complexes (NPCs), which are large multiprotein assemblies made of several copies of a limited number of nucleoporins. A considerable effort has been put into the dissection of mRNA export through NPCs at both cellular and molecular levels, revealing the conserved contributions of a subset of nucleoporins in this process, from yeast to vertebrates. Several reports have also demonstrated the ability of NPCs to sort out properly-processed mRNPs for entry into the nuclear export pathway. Importantly, changes in mRNA export have been associated with post-translational modifications of nucleoporins or changes in NPC composition, depending on cell cycle progression, development or exposure to stress. How NPC modifications also impact on cellular mRNA export in disease situations, notably upon viral infection, is discussed.
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Affiliation(s)
- Amandine Bonnet
- Institut Jacques Monod, CNRS, UMR 7592, University Paris Diderot, Sorbonne Paris Cité, Paris F-75205, France.
| | - Benoit Palancade
- Institut Jacques Monod, CNRS, UMR 7592, University Paris Diderot, Sorbonne Paris Cité, Paris F-75205, France.
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13
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Togashi N, Yamashita A, Sato M, Yamamoto M. Functional significance of nuclear export and mRNA binding of meiotic regulator Spo5 in fission yeast. BMC Microbiol 2014; 14:188. [PMID: 25023750 PMCID: PMC4109790 DOI: 10.1186/1471-2180-14-188] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2013] [Accepted: 07/03/2014] [Indexed: 01/02/2023] Open
Abstract
Background Meiotic cells undergo two rounds of nuclear division and generate gametes. Previous studies have indicated that a number of transcription factors modulate the transcriptome in successive waves during meiosis and spore formation in fission yeast. However, the mechanisms underlying the post-transcriptional regulation in meiosis are not fully understood. The fission yeast spo5+ gene encodes a meiosis-specific RNA-binding protein, which is required for the progression of meiosis II and spore formation. However, the target RNA molecules of Spo5 are yet to be identified. Characterization of meiosis-specific RNA-binding proteins will provide insight into how post-transcriptional regulation influence gene expression during sexual differentiation. Results To assess the functional significance of RNA-recognition motifs (RRMs) of Spo5, we constructed a series of new spo5 truncated mutants and previously reported spo5 missense mutants. In addition, we isolated novel spo5 missense mutants. The phenotypic characteristics of these mutants indicated that the RRMs are essential for both the localization and function of the protein. Interestingly, Spo5 is exported from the nucleus to the cytoplasm via the Rae1-dependent mRNA export pathway, but is unlikely to be involved in global mRNA export. Furthermore, cytoplasmic localization of Spo5 is important for its function, which suggests the involvement of Spo5 in post-transcriptional regulation. We identified pcr1+ mRNA as one of the critical targets of Spo5. The pcr1+ gene encodes an activating transcription factor/cAMP response element binding (ATF/CREB) transcription factor family. Among the four family members, namely Pcr1, Atf1, Atf21, and Atf31, only the mRNA encoding Pcr1 binds to Spo5. Conclusions Spo5 is exported from the nucleus with mRNAs via the Rae1-dependent pathway. RRMs are necessary for this process and also for the function of Spo5 after the nuclear export. Spo5 appears to influence the activity of pcr1+ mRNA, and the mechanism of how Spo5 stimulates the mRNA to promote the progression of meiosis II and spore formation remains an intriguing question for future research.
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Affiliation(s)
| | | | | | - Masayuki Yamamoto
- Kazusa DNA Research Institute, 2-6-7 Kazusa-kamatari, Kisarazu, Chiba 292-0818, Japan.
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14
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Vesiculoviral matrix (M) protein occupies nucleic acid binding site at nucleoporin pair (Rae1 • Nup98). Proc Natl Acad Sci U S A 2014; 111:9127-32. [PMID: 24927547 DOI: 10.1073/pnas.1409076111] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
mRNA export factor 1 (Rae1) and nucleoporin 98 (Nup98) are host cell targets for the matrix (M) protein of vesicular stomatitis virus (VSV). How Rae1 functions in mRNA export and how M protein targets both Rae1 and Nup98 are not understood at the molecular level. To obtain structural insights, we assembled a 1:1:1 complex of M•Rae1•Nup98 and established a crystal structure at 3.15-Å resolution. We found that the M protein contacts the Rae1•Nup98 heterodimer principally by two protrusions projecting from the globular domain of M like a finger and thumb. Both projections clamp to the side of the β-propeller of Rae1, with the finger also contacting Nup98. The most prominent feature of the finger is highly conserved Methionine 51 (Met51) with upstream and downstream acidic residues. The complementary surface on Rae1 displays a deep hydrophobic pocket, into which Met51 fastens like a bolt, and a groove of basic residues on either side, which bond to the acidic residues of the finger. Notably, the M protein competed for in vitro binding of various oligonucleotides to Rae1•Nup98. We localized this competing activity of M to its finger using a synthetic peptide. Collectively, our data suggest that Rae1 serves as a binding protein for the phosphate backbone of any nucleic acid and that the finger of M mimics this ligand. In the context of mRNA export, we propose that a given mRNA segment, after having been deproteinated by helicase, is transiently reproteinated by Nup98-tethered Rae1. We suggest that such repetitive cycles provide cytoplasmic stopover sites required for ratcheting mRNA across the nuclear pore.
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15
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Yarbrough ML, Mata MA, Sakthivel R, Fontoura BMA. Viral subversion of nucleocytoplasmic trafficking. Traffic 2013; 15:127-40. [PMID: 24289861 PMCID: PMC3910510 DOI: 10.1111/tra.12137] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 10/27/2013] [Accepted: 10/31/2013] [Indexed: 12/22/2022]
Abstract
Trafficking of proteins and RNA into and out of the nucleus occurs through the nuclear pore complex (NPC). Because of its critical function in many cellular processes, the NPC and transport factors are common targets of several viruses that disrupt key constituents of the machinery to facilitate viral replication. Many viruses such as poliovirus and severe acute respiratory syndrome (SARS) virus inhibit protein import into the nucleus, whereas viruses such as influenza A virus target and disrupt host mRNA nuclear export. Current evidence indicates that these viruses may employ such strategies to avert the host immune response. Conversely, many viruses co‐opt nucleocytoplasmic trafficking to facilitate transport of viral RNAs. As viral proteins interact with key regulators of the host nuclear transport machinery, viruses have served as invaluable tools of discovery that led to the identification of novel constituents of nuclear transport pathways. This review explores the importance of nucleocytoplasmic trafficking to viral pathogenesis as these studies revealed new antiviral therapeutic strategies and exposed previously unknown cellular mechanisms. Further understanding of nuclear transport pathways will determine whether such therapeutics will be useful treatments for important human pathogens.
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Affiliation(s)
- Melanie L Yarbrough
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX, 75390-9039, USA
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16
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Occhipinti L, Chang Y, Altvater M, Menet AM, Kemmler S, Panse VG. Non-FG mediated transport of the large pre-ribosomal subunit through the nuclear pore complex by the mRNA export factor Gle2. Nucleic Acids Res 2013; 41:8266-79. [PMID: 23907389 PMCID: PMC3783196 DOI: 10.1093/nar/gkt675] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Multiple export receptors passage bound pre-ribosomes through nuclear pore complexes (NPCs) by transiently interacting with the Phe-Gly (FG) meshwork of their transport channels. Here, we reveal how the non-FG interacting yeast mRNA export factor Gly-Leu-FG lethal 2 (Gle2) functions in the export of the large pre-ribosomal subunit (pre-60S). Structure-guided studies uncovered conserved platforms used by Gle2 to export pre-60S: an uncharacterized basic patch required to bind pre-60S, and a second surface that makes non-FG contacts with the nucleoporin Nup116. A basic patch mutant of Gle2 is able to function in mRNA export, but not pre-60S export. Thus, Gle2 provides a distinct interaction platform to transport pre-60S to the cytoplasm. Notably, Gle2’s interaction platforms become crucial for pre-60S export when FG-interacting receptors are either not recruited to pre-60S or are impaired. We propose that large complex cargos rely on non-FG as well as FG-interactions for their efficient translocation through the nuclear pore complex channel.
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Affiliation(s)
- Laura Occhipinti
- Department of Biology (D-BIOL), Institute of Biochemistry (IBC), ETH Zurich, Schafmattstrasse 18, CH-8093 Zurich, Switzerland and MLS Program, Life Sciences Zurich Graduate School, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland
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17
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Kuss SK, Mata MA, Zhang L, Fontoura BMA. Nuclear imprisonment: viral strategies to arrest host mRNA nuclear export. Viruses 2013; 5:1824-49. [PMID: 23872491 PMCID: PMC3738964 DOI: 10.3390/v5071824] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2013] [Revised: 06/27/2013] [Accepted: 07/11/2013] [Indexed: 12/15/2022] Open
Abstract
Viruses possess many strategies to impair host cellular responses to infection. Nuclear export of host messenger RNAs (mRNA) that encode antiviral factors is critical for antiviral protein production and control of viral infections. Several viruses have evolved sophisticated strategies to inhibit nuclear export of host mRNAs, including targeting mRNA export factors and nucleoporins to compromise their roles in nucleo-cytoplasmic trafficking of cellular mRNA. Here, we present a review of research focused on suppression of host mRNA nuclear export by viruses, including influenza A virus and vesicular stomatitis virus, and the impact of this viral suppression on host antiviral responses.
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Affiliation(s)
- Sharon K Kuss
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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18
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Complexes of vesicular stomatitis virus matrix protein with host Rae1 and Nup98 involved in inhibition of host transcription. PLoS Pathog 2012; 8:e1002929. [PMID: 23028327 PMCID: PMC3460625 DOI: 10.1371/journal.ppat.1002929] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2012] [Accepted: 08/13/2012] [Indexed: 11/19/2022] Open
Abstract
Vesicular stomatitis virus (VSV) suppresses antiviral responses in infected cells by inhibiting host gene expression at multiple levels, including transcription, nuclear cytoplasmic transport, and translation. The inhibition of host gene expression is due to the activity of the viral matrix (M) protein. Previous studies have shown that M protein interacts with host proteins Rae1 and Nup98 that have been implicated in regulating nuclear-cytoplasmic transport. However, Rae1 function is not essential for host mRNA transport, raising the question of how interaction of a viral protein with a host protein that is not essential for gene expression causes a global inhibition at multiple levels. We tested the hypothesis that there may be multiple M protein-Rae1 complexes involved in inhibiting host gene expression at multiple levels. Using size exclusion chromatography and sedimentation velocity analysis, it was determined that Rae1 exists in high, intermediate, and low molecular weight complexes. The intermediate molecular weight complexes containing Nup98 interacted most efficiently with M protein. The low molecular weight form also interacted with M protein in cells that overexpress Rae1 or cells in which Nup98 expression was silenced. Silencing Rae1 expression had little if any effect on nuclear accumulation of host mRNA in VSV-infected cells, nor did it affect VSV's ability to inhibit host translation. Instead, silencing Rae1 expression reduced the ability of VSV to inhibit host transcription. M protein interacted efficiently with Rae1-Nup98 complexes associated with the chromatin fraction of host nuclei, consistent with an effect on host transcription. These results support the idea that M protein-Rae1 complexes serve as platforms to promote the interaction of M protein with other factors involved in host transcription. They also support the idea that Rae1-Nup98 complexes play a previously under-appreciated role in regulation of transcription. All viruses have mechanisms to suppress or evade host antiviral responses. These mechanisms are critical for viral pathogenicity. Vesicular stomatitis virus (VSV) suppresses antiviral responses by global inhibition of host gene expression mediated by the viral matrix (M) protein. M protein interacts with the host protein Rae1 in a complex with the nucleoporin Nup98. It had been thought that interaction of M protein with Rae1 blocks nuclear-cytoplasmic mRNA transport. However, other data show that Rae1 is not essential for mRNA transport. With this discrepancy in mind, we re-examined the interaction of M protein with Rae1 and Nup98 and the level of host gene expression in which they are involved. A key result was that silencing Rae1 expression did not affect host gene expression, but instead increased cellular resistance to inhibition by M protein. Furthermore, silencing Rae1 expression primarily affected the inhibition of host transcription with no significant effect on nuclear accumulation of mRNA. These results support a model in which Rae1 serves as a “platform” to promote interaction of M protein with cellular targets involved in host transcription. This illustrates a general principle that viral proteins can have multiple cellular effects by interacting with host proteins that are themselves multi-functional.
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19
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Funasaka T, Wong RW. The role of nuclear pore complex in tumor microenvironment and metastasis. Cancer Metastasis Rev 2011; 30:239-51. [PMID: 21298575 DOI: 10.1007/s10555-011-9287-y] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
One of the main reasons for cancer mortality is caused by the highly invasive behavior of cancer cells, which often due to aggressive metastasis. Metastasis is mediated by various growth factors and cytokines, operating through numerous signaling pathways. Remarkably, all these metastatic signaling pathways must enter the nucleus through a single gatekeeper, the nuclear pore complex (NPC). NPCs are the only gateway between the cytoplasm and the nucleus. NPCs are among the largest proteinaceous assemblies in the cell and are composed of multiple copies of around 30 different proteins called nucleoporins. Here, we review what is currently known about the NPC, and its role in the mechanisms of tumor progression. We will also explore potential strategies to target metastatic pathways by manipulating the karyopherins (importins/exportins) of nucleocytoplasmic traffic through NPCs.
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Affiliation(s)
- Tatsuyoshi Funasaka
- Frontier Science Organization, 1/F Cancer Research Institute, Kanazawa University, Kanazawa, Ishikawa, 920-1192, Japan
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20
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Wozniak R, Burke B, Doye V. Nuclear transport and the mitotic apparatus: an evolving relationship. Cell Mol Life Sci 2010; 67:2215-30. [PMID: 20372967 PMCID: PMC11115906 DOI: 10.1007/s00018-010-0325-7] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Accepted: 02/17/2010] [Indexed: 10/19/2022]
Abstract
The trafficking of macromolecules between the cytoplasm and the nucleus is controlled by the nuclear pore complexes (NPCs) and various transport factors that facilitate the movement of cargos through the NPCs and their accumulation in the target compartment. While their functions in transport are well established, an ever-growing number of observations have also linked components of the nuclear transport machinery to processes that control chromosome segregation during mitosis, including spindle assembly, kinetochore function, and the spindle assembly checkpoint. In this review, we will discuss this evolving area of study and emerging hypotheses that propose key roles for components of the nuclear transport apparatus in mitotic progression.
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Affiliation(s)
- Richard Wozniak
- Department of Cell Biology, University of Alberta, Edmonton, AB, T6G 2H7, Canada.
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21
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Iwamoto M, Asakawa H, Hiraoka Y, Haraguchi T. Nucleoporin Nup98: a gatekeeper in the eukaryotic kingdoms. Genes Cells 2010; 15:661-9. [PMID: 20545767 DOI: 10.1111/j.1365-2443.2010.01415.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The nucleoporin Nup98 is an essential component of the nuclear pore complex. This peripheral nucleoporin with its Gly-Leu-Phe-Gly (GLFG) repeat domain contributes to nuclear-cytoplasmic trafficking, including mRNA export. In addition, accumulating studies indicate that Nup98 plays roles in several important biological events such as gene expression, mitotic checkpoint, and pathogenesis. Nup98 is well conserved among organisms belonging to the fungi and animal kingdoms. These kingdoms belong to the eukaryotic supergroup Opisthokonta. However, there is considerable diversity in the Nup98 orthologs expressed in organisms belonging to other eukaryotic supergroups. Intriguingly, in ciliates, a unicellular organism having two functionally distinct nuclei, GLFG-Nup98 is present in one of the nuclei and a distinct Nup98 ortholog is present in the other nucleus, and these different Nup98s participate in a nucleus-selective transport mechanism. In this review, we focus on Nup98 function and discuss how this nucleoporin has evolved in eukaryotic kingdoms.
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Affiliation(s)
- Masaaki Iwamoto
- Kobe Advanced ICT Research Center, National Institute of Information and Communications Technology, Japan
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22
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Structural and functional analysis of the interaction between the nucleoporin Nup98 and the mRNA export factor Rae1. Proc Natl Acad Sci U S A 2010; 107:10406-11. [PMID: 20498086 DOI: 10.1073/pnas.1005389107] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
The export of mRNAs is a multistep process, involving the packaging of mRNAs into messenger ribonucleoprotein particles (mRNPs), their transport through nuclear pore complexes, and mRNP remodeling events prior to translation. Ribonucleic acid export 1 (Rae1) and Nup98 are evolutionarily conserved mRNA export factors that are targeted by the vesicular stomatitis virus matrix protein to inhibit host cell nuclear export. Here, we present the crystal structure of human Rae1 in complex with the Gle2-binding sequence (GLEBS) of Nup98 at 1.65 A resolution. Rae1 forms a seven-bladed beta-propeller with several extensive surface loops. The Nup98 GLEBS motif forms an approximately 50-A-long hairpin that binds with its C-terminal arm to an essentially invariant hydrophobic surface that extends over the entire top face of the Rae1 beta-propeller. The C-terminal arm of the GLEBS hairpin is necessary and sufficient for Rae1 binding, and we identify a tandem glutamate element in this arm as critical for complex formation. The Rae1*Nup98(GLEBS) surface features an additional conserved patch with a positive electrostatic potential, and we demonstrate that the complex possesses single-stranded RNA-binding capability. Together, these data suggest that the Rae1*Nup98 complex directly binds to the mRNP at several stages of the mRNA export pathway.
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23
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Lee JY, Lee HS, Wi SJ, Park KY, Schmit AC, Pai HS. Dual functions of Nicotiana benthamiana Rae1 in interphase and mitosis. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2009; 59:278-91. [PMID: 19392703 DOI: 10.1111/j.1365-313x.2009.03869.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Rae1 performs multiple functions in animal systems, acting in interphase as an mRNA export factor and during mitosis as a mitotic checkpoint and spindle assembly regulator. In this study we characterized multiple functions of Rae1 in plants. Virus-induced gene silencing of Nicotiana benthamiana Rae1, NbRae1, which encodes a protein with four WD40 repeats, resulted in growth arrest and abnormal leaf development. NbRae1 was mainly associated with the nuclear envelope during interphase, and NbRae1 deficiency caused accumulation of poly(A) RNA in the nuclei of leaf cells, suggesting defective mRNA export. In the shoot apex, depletion of NbRae1 led to reduced mitotic activities, accompanied by reduced cyclin-dependent kinase (CDK) activity and decreased expression of cyclin B1, CDKB1-1, and histones H3 and H4. The secondary growth of stem vasculature was also inhibited, indicating reduced cambial activities. Differentiated leaf cells of NbRae1-silenced plants exhibited elevated ploidy levels. Immunolabeling in BY-2 cells showed that NbRae1 protein localized to mitotic microtubules and the cell plate-forming zone during mitosis, and recombinant NbRae1 directly bound to microtubules in vitro. Inhibition of NbRae1 expression in BY-2 cells using a beta-estradiol-inducible RNAi system resulted in severe defects in spindle organization and chromosome alignment and segregation, which correlated with delays in cell cycle progression. Together, these results suggest that NbRae1 plays a dual role in mRNA export in interphase and in spindle assembly in mitosis.
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Affiliation(s)
- Jae-Yong Lee
- Department of Biology, Yonsei University, Seoul 120-749, Korea
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24
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Cohesin subunit SMC1 associates with mitotic microtubules at the spindle pole. Proc Natl Acad Sci U S A 2008; 105:15441-5. [PMID: 18832153 DOI: 10.1073/pnas.0807660105] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Accurate mitotic chromosome segregation depends on the formation of a microtubule-based bipolar spindle apparatus. We report that the cohesin subunit structural maintenance of chromosomes subunit 1 (SMC1) is recruited to microtubule-bound RNA export factor 1 (Rae1) at the mitotic spindle pole. We locate the Rae1-binding site to a 21-residue-long region, SMC1(947-967) and provide several lines of evidence that phosphorylation of Ser(957) and Ser(966) of SMC1 stimulates binding to Rae1. Imbalances in these assembly pathways caused formation of multipolar spindles. Our data suggest that cohesin's known bundling function for chromatids in mitotic and interphase cells extends to microtubules at the spindle pole.
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25
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NFAR-1 and -2 modulate translation and are required for efficient host defense. Proc Natl Acad Sci U S A 2008; 105:4173-8. [PMID: 18337511 DOI: 10.1073/pnas.0711222105] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
We report here that the alternatively spliced nuclear factors associated with double-stranded RNA, NFAR-1 (90 kDa) and -2 (110 kDa), are involved in retaining cellular transcripts in intranuclear foci and can regulate the export of mRNA to the cytoplasm. Furthermore, the NFAR proteins were found to remain associated with exported ribonucleoprotein complexes. Loss of NFAR function, which was embryonic-lethal, caused an increase in protein synthesis rates, an effect augmented by the presence of the mRNA export factors TAP, p15, or Rae1. Significantly, NFAR depletion in normal murine fibroblasts rendered these cells dramatically susceptible to vesicular stomatitis virus replication. Collectively, our data demonstrate that the NFARs exert influence on mRNA trafficking and the modulation of translation rates and may constitute an innate immune translational surveillance mechanism important in host defense countermeasures against virus infection.
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Satterly N, Tsai PL, van Deursen J, Nussenzveig DR, Wang Y, Faria PA, Levay A, Levy DE, Fontoura BMA. Influenza virus targets the mRNA export machinery and the nuclear pore complex. Proc Natl Acad Sci U S A 2007; 104:1853-8. [PMID: 17267598 PMCID: PMC1794296 DOI: 10.1073/pnas.0610977104] [Citation(s) in RCA: 228] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The NS1 protein of influenza A virus is a major virulence factor that is essential for pathogenesis. NS1 functions to impair innate and adaptive immunity by inhibiting host signal transduction and gene expression, but its mechanisms of action remain to be fully elucidated. We show here that NS1 forms an inhibitory complex with NXF1/TAP, p15/NXT, Rae1/mrnp41, and E1B-AP5, which are key constituents of the mRNA export machinery that interact with both mRNAs and nucleoporins to direct mRNAs through the nuclear pore complex. Increased levels of NXF1, p15, or Rae1 revert the mRNA export blockage induced by NS1. Furthermore, influenza virus down-regulates Nup98, a nucleoporin that is a docking site for mRNA export factors. Reduced expression of these mRNA export factors renders cells highly permissive to influenza virus replication, demonstrating that proper levels of key constituents of the mRNA export machinery protect against influenza virus replication. Because Nup98 and Rae1 are induced by interferons, down-regulation of this pathway is likely a viral strategy to promote viral replication. These findings demonstrate previously undescribed influenza-mediated viral-host interactions and provide insights into potential molecular therapies that may interfere with influenza infection.
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Affiliation(s)
- Neal Satterly
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039
| | - Pei-Ling Tsai
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039
| | - Jan van Deursen
- Department of Pediatrics and Adolescent Medicine, Mayo Clinic, Rochester, MN 55905
| | - Daniel R. Nussenzveig
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039
- Department of Pathology, University of Texas Southwestern Medical Center, Dallas, TX 75390
| | - Yaming Wang
- Department of Pathology, New York University School of Medicine, New York, NY 10016; and
| | - Paula A. Faria
- Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, Miami, FL 33136
| | - Agata Levay
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039
- Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, Miami, FL 33136
| | - David E. Levy
- Department of Pathology, New York University School of Medicine, New York, NY 10016; and
| | - Beatriz M. A. Fontoura
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039
- To whom correspondence should be addressed. E-mail:
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27
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Wong RW, Blobel G, Coutavas E. Rae1 interaction with NuMA is required for bipolar spindle formation. Proc Natl Acad Sci U S A 2006; 103:19783-7. [PMID: 17172455 PMCID: PMC1750899 DOI: 10.1073/pnas.0609582104] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
In eukaryotic cells, the faithful segregation of daughter chromosomes during cell division depends on formation of a microtubule (MT)-based bipolar spindle apparatus. The Nuclear Mitotic Apparatus protein (NuMA) is recruited from interphase nuclei to spindle MTs during mitosis. The carboxy terminal domain of NuMA binds MTs, allowing a NuMA dimer to function as a "divalent" crosslinker that bundles MTs. The messenger RNA export factor, Rae1, also binds to MTs. Lowering Rae1 or increasing NuMA levels in cells results in spindle abnormalities. We have identified a mitotic-specific interaction between Rae1 and NuMA and have explored the relationship between Rae1 and NuMA in spindle formation. We have mapped a specific binding site for Rae1 on NuMA that would convert a NuMA dimer to a "tetravalent" crosslinker of MTs. In mitosis, reducing Rae1 or increasing NuMA concentration would be expected to alter the valency of NuMA toward MTs; the "density" of NuMA-MT crosslinks in these conditions would be diminished, even though a threshold number of crosslinks sufficient to stabilize aberrant multipolar spindles may form. Consistent with this interpretation, we found that coupling NuMA overexpression to Rae1 overexpression or coupling Rae1 depletion to NuMA depletion prevented the formation of aberrant spindles. Likewise, we found that overexpression of the specific Rae1-binding domain of NuMA in HeLa cells led to aberrant spindle formation. These data point to the Rae1-NuMA interaction as a critical element for normal spindle formation in mitosis.
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Affiliation(s)
- Richard W. Wong
- Laboratory of Cell Biology, Howard Hughes Medical Institute, The Rockefeller University, New York, NY 10021
| | - Günter Blobel
- Laboratory of Cell Biology, Howard Hughes Medical Institute, The Rockefeller University, New York, NY 10021
- *To whom correspondence may be addressed. E-mail:
or
| | - Elias Coutavas
- Laboratory of Cell Biology, Howard Hughes Medical Institute, The Rockefeller University, New York, NY 10021
- *To whom correspondence may be addressed. E-mail:
or
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28
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Chakraborty P, Satterly N, Fontoura BMA. Nuclear export assays for poly(A) RNAs. Methods 2006; 39:363-9. [PMID: 16935004 DOI: 10.1016/j.ymeth.2006.07.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2006] [Accepted: 07/13/2006] [Indexed: 10/24/2022] Open
Abstract
Nuclear export of mRNAs is a central step in eukaryotic gene expression. A defect in bulk poly(A) RNA export can be caused either by a direct disruption of the mRNA export machinery or by an indirect effect on mRNA biogenesis. One example of interference with the mRNA export pathway is viral-host interactions involving mRNA export factors. VSV M protein binds the mRNA export factor Rae1 that is in complex with Nup98, resulting in nuclear retention of mRNAs. To study regulation of mRNA export, we review here two useful methodologies, which include a reporter gene assay and oligo(dT) in situ hybridization. In a reporter gene assay one can assess up-regulation or down-regulation of gene expression that can occur at different levels, including transcription, mRNA processing, mRNA export, and translation. An effect on mRNA export can then be identified by determining the intracellular distribution of poly(A) RNA using oligo(dT) in situ hybridization. Reporter gene assays are quick, relatively simple and can thus be used in primary highthroughput screenings. To further pinpoint disruption of mRNA export, oligo(dT) in situ hybridization can be used. Since it is a more laborious methodology it is more suitable for a secondary screening. We also review here a combination of oligo(dT) in situ hybridization with immunofluorescence for simultaneous localization of endogenous or ectopically expressed proteins. Altogether, these assays are valuable tools for identifying major regulatory effects on mRNA nuclear export.
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Affiliation(s)
- Papia Chakraborty
- Department of Cell Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390-9039, USA
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29
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Baker DJ, Jeganathan KB, Malureanu L, Perez-Terzic C, Terzic A, van Deursen JMA. Early aging-associated phenotypes in Bub3/Rae1 haploinsufficient mice. ACTA ACUST UNITED AC 2006; 172:529-40. [PMID: 16476774 PMCID: PMC2063673 DOI: 10.1083/jcb.200507081] [Citation(s) in RCA: 150] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Aging is a highly complex biological process that is believed to involve multiple mechanisms. Mice that have small amounts of the mitotic checkpoint protein BubR1 age much faster than normal mice, but whether other mitotic checkpoint genes function to prevent the early onset of aging is unknown. In this study, we show that several aging-associated phenotypes appear early in mice that are double haploinsufficient for the mitotic checkpoint genes Bub3 and Rae1 but not in mice that are single haploinsufficient for these genes. Mouse embryonic fibroblasts (MEFs) from Bub3/Rae1 haploinsufficient mice undergo premature senescence and accumulate high levels of p19, p53, p21, and p16, whereas MEFs from single haploinsufficient mice do not. Furthermore, although BubR1 hypomorphic mice have less aneuploidy than Bub3/Rae1 haploinsufficient mice, they age much faster. Our findings suggest that early onset of aging-associated phenotypes in mice with mitotic checkpoint gene defects is linked to cellular senescence and activation of the p53 and p16 pathways rather than to aneuploidy.
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Affiliation(s)
- Darren J Baker
- Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN 55905, USA
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30
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Ball JR, Ullman KS. Versatility at the nuclear pore complex: lessons learned from the nucleoporin Nup153. Chromosoma 2005; 114:319-30. [PMID: 16133350 DOI: 10.1007/s00412-005-0019-3] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2005] [Revised: 07/08/2005] [Accepted: 07/10/2005] [Indexed: 10/25/2022]
Abstract
The vertebrate pore protein Nup153 plays pivotal roles in nuclear pore function. In addition to being important to pore architecture, Nup153 is a key participant in both import and export. The scope of Nup153 function also extends beyond the canonical view of the pore as a trafficking gateway. During the transition into mitosis, Nup153 directs proteins involved in membrane remodeling to the nuclear envelope. As cells exit mitosis, Nup153 is recruited to the chromosomal surface, where nuclear pores are formed anew in a complicated process still under much experimental scrutiny. In addition, Nup153 is targeted for protease cleavage during apoptosis and in response to certain viral infections, providing molecular insight into pore reconfiguration during cell response. Overall, the versatile nature of Nup153 underscores an emerging view of the nuclear pore at the nexus of many key cellular processes.
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Affiliation(s)
- Jennifer R Ball
- Department of Oncological Sciences, Huntsman Cancer Institute, 2000 Circle of Hope, University of Utah, Salt Lake City, UT 84112, USA
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31
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Thakurta AG, Gopal G, Yoon JH, Kozak L, Dhar R. Homolog of BRCA2-interacting Dss1p and Uap56p link Mlo3p and Rae1p for mRNA export in fission yeast. EMBO J 2005; 24:2512-23. [PMID: 15990877 PMCID: PMC1176449 DOI: 10.1038/sj.emboj.7600713] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2005] [Accepted: 05/19/2005] [Indexed: 11/09/2022] Open
Abstract
The breast cancer tumor suppressor BRCA2-interacting protein, DSS1, and its homologs are critical for DNA recombination in eukaryotic cells. We found that Dss1p, along with Mlo3p and Uap56p, Schizosaccharomyces pombe homologs of two messenger RNA (mRNA) export factors of the NXF-NXT pathway, is required for mRNA export in S. pombe. Previously, we showed that the nuclear pore-associated Rae1p is an essential mRNA export factor in S. pombe. Here, we show that Dss1p and Uap56p function by linking mRNA adapter Mlo3p to Rae1p for targeting mRNA-protein complex (mRNP) to the proteins of the nuclear pore complex (NPC). Dss1p preferentially recruits to genes in vivo and interacts with -FG (phenylalanine glycine) nucleoporins in vivo and in vitro. Thus, Dss1p may function at multiple steps of mRNA export, from mRNP biogenesis to their targeting and translocation through the NPC.
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Affiliation(s)
- Anjan G Thakurta
- Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Ganesh Gopal
- Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Jin Ho Yoon
- Department of Biology, College of Natural Sciences, Sungshin Women's University, South Korea
| | - Libor Kozak
- Center of Molecular Biology and Gene Therapy, University Hospital Brno, Czech Republic
| | - Ravi Dhar
- Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
- Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA. Tel.: +1 301 496 0990; Fax: +1 301 480 5088; E-mail:
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32
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Blower MD, Nachury M, Heald R, Weis K. A Rae1-containing ribonucleoprotein complex is required for mitotic spindle assembly. Cell 2005; 121:223-34. [PMID: 15851029 DOI: 10.1016/j.cell.2005.02.016] [Citation(s) in RCA: 214] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2004] [Revised: 12/23/2004] [Accepted: 02/10/2005] [Indexed: 11/18/2022]
Abstract
Centrosome-independent microtubule polymerization around chromosomes has been shown to require a local gradient of RanGTP, which discharges mitotic cargoes from the nuclear import receptor importin beta. Here, we have used an activity-based assay in Xenopus egg extracts to purify the mRNA export protein Rae1 as a spindle assembly factor regulated by this pathway. Rae1 is a microtubule-associated protein that binds directly to importin beta. Depletion of Rae1 from extracts or cells severely inhibits mitotic spindle assembly. A purified Rae1 complex stabilizes microtubules in egg extracts in a RanGTP/importin beta-regulated manner. Interestingly, Rae1 exists in a large ribonucleoprotein complex, which requires RNA for its activity to control microtubule dynamics in vitro. Furthermore, we provide evidence that RNA associates with the mitotic spindle and that it plays a direct, translation-independent role in spindle assembly. Our studies reveal an unexpected function for RNA in spindle morphogenesis.
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Affiliation(s)
- Michael D Blower
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, California 94720, USA
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33
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Faria PA, Chakraborty P, Levay A, Barber GN, Ezelle HJ, Enninga J, Arana C, van Deursen J, Fontoura BMA. VSV disrupts the Rae1/mrnp41 mRNA nuclear export pathway. Mol Cell 2005; 17:93-102. [PMID: 15629720 DOI: 10.1016/j.molcel.2004.11.023] [Citation(s) in RCA: 183] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2004] [Revised: 09/11/2004] [Accepted: 11/04/2004] [Indexed: 12/17/2022]
Abstract
Interference with nucleocytoplasmic transport is a strategy employed by certain viruses to compromise host cellular function. While it has been shown that the matrix (M) protein of the vesicular stomatitis virus (VSV) inhibits nuclear export of host cell mRNAs, the underlying mechanism has not been fully established. Here we show that VSV M protein binds the mRNA export factor Rae1/mrnp41. A mutant of M protein defective in Rae1 binding is unable to inhibit mRNA nuclear export. We further show that increased expression of Rae1 fully reverts the inhibition of mRNA export induced by M protein or following virus infection. We found that Rae1 is induced by interferon-gamma, a cytokine that plays a critical role in the immune response to viruses, such as VSV. Thus, these results demonstrate that VSV M protein blocks mRNA export by disrupting Rae1 function, which can be reverted by induction of Rae1 expression.
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Affiliation(s)
- Paula A Faria
- Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, Miami, FL 33136, USA
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34
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Maggipinto M, Rabiner C, Kidd GJ, Hawkins AJ, Smith R, Barbarese E. Increased expression of the MBP mRNA binding protein HnRNP A2 during oligodendrocyte differentiation. J Neurosci Res 2004; 75:614-23. [PMID: 14991837 DOI: 10.1002/jnr.20014] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Heterogeneous nuclear ribonucleoprotein (hnRNP) A2, a trans-acting factor that mediates intracellular trafficking of myelin basic protein (MBP) mRNA to the myelin compartment in oligodendrocytes, is most abundant in the nucleus, but shuttles between the nucleus and cytoplasm. In the cytoplasm, it is associated with granules that transport mRNA from the cell body to the processes of oligodendrocytes. We found that the overall level of hnRNP A2 increased in oligodendrocytes as they differentiated into MBP-positive cells, and that this augmentation was reflected primarily in the cytoplasmic pool of hnRNP A2 present in the form of granules. The extranuclear distribution of hnRNP A2 was also observed in brain during the period of myelination in vivo. Methylation and phosphorylation have been implicated previously in the nuclear to cytoplasmic distribution of hnRNPs, so we used drugs that block methylation and phosphorylation of hnRNPs to assess their effect on hnRNP A2 distribution and mRNA trafficking. Cultures treated with adenosine dialdehyde (AdOx), an inhibitor of S-adenosyl-L-homocysteine hydrolase, or with 5,6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB), a drug that inhibits casein kinase 2 (CK2), maintained the preferential nuclear distribution of hnRNP A2. Treatment with either drug affected the transport of RNA trafficking granules that remained confined to the cell body.
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Affiliation(s)
- M Maggipinto
- Department of Neuroscience, University of Connecticut Health Center, Farmington
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35
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Chuong SDX, Good AG, Taylor GJ, Freeman MC, Moorhead GBG, Muench DG. Large-scale identification of tubulin-binding proteins provides insight on subcellular trafficking, metabolic channeling, and signaling in plant cells. Mol Cell Proteomics 2004; 3:970-83. [PMID: 15249590 DOI: 10.1074/mcp.m400053-mcp200] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Microtubules play an essential role in the growth and development of plants and are known to be involved in regulating many cellular processes ranging from translation to signaling. In this article, we describe the proteomic characterization of Arabidopsis tubulin-binding proteins that were purified using tubulin affinity chromatography. Microtubule co-sedimentation assays indicated that most, if not all, of the proteins in the tubulin-binding protein fraction possessed microtubule-binding activity. Two-dimensional gel electrophoresis of the tubulin-binding protein fraction was performed, and 86 protein spots were excised and analyzed for protein identification. A total of 122 proteins were identified with high confidence using LC-MS/MS. These proteins were grouped into six categories based on their predicted functions: microtubule-associated proteins, translation factors, RNA-binding proteins, signaling proteins, metabolic enzymes, and proteins with other functions. Almost one-half of the proteins identified in this fraction were related to proteins that have previously been reported to interact with microtubules. This study represents the first large-scale proteomic identification of eukaryotic cytoskeleton-binding proteins, and provides insight on subcellular trafficking, metabolic channeling, and signaling in plant cells.
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Affiliation(s)
- Simon D X Chuong
- Department of Biological Sciences, University of Calgary, Calgary, Alberta T2N 1N4, Canada
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36
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Dimaano C, Ullman KS. Nucleocytoplasmic transport: integrating mRNA production and turnover with export through the nuclear pore. Mol Cell Biol 2004; 24:3069-76. [PMID: 15060131 PMCID: PMC381686 DOI: 10.1128/mcb.24.8.3069-3076.2004] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Affiliation(s)
- Christian Dimaano
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah 84112, USA
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37
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Jans DA, Thomas RJ, Gillespie MT. Parathyroid hormone-related protein (PTHrP): a nucleocytoplasmic shuttling protein with distinct paracrine and intracrine roles. VITAMINS AND HORMONES 2003; 66:345-84. [PMID: 12852260 DOI: 10.1016/s0083-6729(03)01010-0] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Parathyroid hormone-related protein (PTHrP) was first discovered as a circulating factor secreted by certain cancers responsible for the syndrome of humoral hypercalcemia of malignancy. PTHrP possesses distinct paracrine and intracrine signaling roles. The similarity of its N-terminus to that of parathyroid hormone (PTH) enables it to share PTH's paracrine signaling properties, whereas the rest of the molecule possesses other functions, largely relating to an intracrine signaling role in the nucleus/nucleolus in regulating apoptosis and cell proliferation. Recent advances have shown that intracellularly expressed PTHrP is able to shuttle in cell-cycle- and signal-dependent fashion between nucleus and cytoplasm through the action of the distinct intracellular transport receptors importin beta 1 and exportin 1 (Crm1) mediating nuclear import and export of PTHrP, respectively. Together, the import and export pathways constitute an integrated system for PTHrP subcellular localization. Intriguingly, PTHrP nuclear/nucleolar import is dependent on microtubule integrity, transport to the nucleus appearing to occur in vectorial fashion along microtubules, mediated in part by the action of importin beta 1. PTHrP has recently been shown to be able to bind to RNA, meaning that PTHrP's nucleocytoplasmic shuttling ability may relate to a specific role within the nucleus/nucleolus to regulate RNA synthesis and/or transport.
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Affiliation(s)
- David A Jans
- Nuclear Signalling Laboratory, Department of Biochemistry and Molecular Biology, Monash University, Monash University 3800, Australia
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38
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Blevins MB, Smith AM, Phillips EM, Powers MA. Complex formation among the RNA export proteins Nup98, Rae1/Gle2, and TAP. J Biol Chem 2003; 278:20979-88. [PMID: 12637516 DOI: 10.1074/jbc.m302061200] [Citation(s) in RCA: 111] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Most nucleocytoplasmic traffic through the nuclear pore complex is mediated by soluble receptors of the importin/exportin or karyopherin family. mRNA export is unique in that no receptor of this family has been implicated in trafficking of the bulk of mRNAs. Instead, many diverse proteins have been linked to mRNA export, but an all-encompassing model remains elusive. Understanding how these proteins interact with each other is central to the development of such a model. Here, we have focused on the interactions between three proteins implicated in mRNA export, Nup98, Rae1/Gle2, and TAP. We have defined the binary complexes that form among these proteins. We find that Gle2 requires two sites within TAP for stable interaction. Strikingly, rather than a general affinity for all nucleoporin FG repeats, TAP has highest affinity for a specific region within the GLFG domain of Nup98, indicating that not all repeats are identical in function. We have established that the ternary complex can form through simultaneous binding of both Gle2 and TAP to adjacent sites on Nup98. In contrast, Nup98 competes with TAP for Gle2 binding; when bound to Nup98, Gle2 no longer interacts directly with TAP. From these interactions, we propose that Gle2 may act to deliver TAP to Nup98 and that this may represent the first in a series of interactions between an export complex and a nucleoporin.
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Affiliation(s)
- Melanie B Blevins
- Department of Cell Biology, Emory University School of Medicine, Atlanta, Georgia 30322, USA
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39
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Babu JR, Jeganathan KB, Baker DJ, Wu X, Kang-Decker N, van Deursen JM. Rae1 is an essential mitotic checkpoint regulator that cooperates with Bub3 to prevent chromosome missegregation. J Cell Biol 2003; 160:341-53. [PMID: 12551952 PMCID: PMC2172680 DOI: 10.1083/jcb.200211048] [Citation(s) in RCA: 276] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The WD-repeat proteins Rae1 and Bub3 show extensive sequence homology, indicative of functional similarity. However, previous studies have suggested that Rae1 is involved in the mRNA export pathway and Bub3 in the mitotic checkpoint. To determine the in vivo roles of Rae1 and Bub3 in mammals, we generated knockout mice that have these genes deleted individually or in combination. Here we show that haplo-insufficiency of either Rae1 or Bub3 results in a similar phenotype involving mitotic checkpoint defects and chromosome missegregation. We also show that overexpression of Rae1 can correct for Rae1 haplo-insufficiency and, surprisingly, Bub3 haplo-insufficiency. Rae1-null and Bub3-null mice are embryonic lethal, although cells from these mice did not have a detectable defect in nuclear export of mRNA. Unlike null mice, compound haplo-insufficient Rae1/Bub3 mice are viable. However, cells from these mice exhibit much greater rates of premature sister chromatid separation and chromosome missegregation than single haplo-insufficient cells. Finally, we show that mice with mitotic checkpoint defects are more susceptible to dimethylbenzanthrene-induced tumorigenesis than wild-type mice. Thus, our data demonstrate a novel function for Rae1 and characterize Rae1 and Bub3 as related proteins with essential, overlapping, and cooperating roles in the mitotic checkpoint.
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Affiliation(s)
- J Ramesh Babu
- Department of Pediatric and Adolescent Medicine, Mayo Clinic, Rochester, MN 55905, USA
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40
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41
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Sabri N, Farrants AKO, Hellman U, Visa N. Evidence for a posttranscriptional role of a TFIIICalpha-like protein in Chironomus tentans. Mol Biol Cell 2002; 13:1765-77. [PMID: 12006668 PMCID: PMC111142 DOI: 10.1091/mbc.01-09-0436] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
We have cloned and sequenced a cDNA that encodes for a nuclear protein of 238 kDa in the dipteran Chironomus tentans. This protein, that we call p2D10, is structurally similar to the alpha subunit of the general transcription factor TFIIIC. Using immunoelectron microscopy we have shown that a fraction of p2D10 is located at sites of transcription, which is consistent with a possible role of this protein in transcription initiation. We have also found that a large fraction of p2D10 is located in the nucleoplasm and in the nuclear pore complexes. Using gel filtration chromatography and coimmunoprecipitation methods, we have identified and characterized two p2D10-containing complexes that differ in molecular mass and composition. The heavy p2D10-containing complex contains at least one other component of the TFIIIC complex, TFIIIC-epsilon. Based on its molecular mass and composition, the heavy p2D10-containing complex may be the Pol III holoenzyme. The light p2D10-containing complex contains RNA together with at least two proteins that are thought to be involved in mRNA trafficking, RAE1 and hrp65. The observations reported here suggest that this new TFIIIC-alpha-like protein is involved in posttranscriptional steps of premRNA metabolism in Chironomus tentans.
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Affiliation(s)
- Nafiseh Sabri
- Department of Molecular Biology and Functional Genomics, Stockholm University, SE-10691, Sweden
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42
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Abstract
Recent advances have led to a new understanding of how mRNAs are exported from the nucleus to the cytoplasm. This process requires a heterodimeric mRNA export receptor that is part of an elaborate machinery conserved from yeast to humans. Export of mRNAs is coupled to upstream steps in gene expression, such as pre-mRNA splicing, and to downstream events, including nonsense-mediated decay.
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Affiliation(s)
- Robin Reed
- Department of Cell Biology, Harvard Medical School, Boston, MA 02115, USA.
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43
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Zolotukhin AS, Tan W, Bear J, Smulevitch S, Felber BK. U2AF participates in the binding of TAP (NXF1) to mRNA. J Biol Chem 2002; 277:3935-42. [PMID: 11724776 DOI: 10.1074/jbc.m107598200] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
TAP/NXF1 is a conserved mRNA export receptor serving as a link between messenger ribonucleoproteins (mRNPs) and the nuclear pore complex. The mechanism by which TAP recognizes its export substrate is unclear. We show here that TAP is added to spliced mRNP in human cells. We identified a distinct region of TAP that targets it to mRNP. Using yeast two-hybrid screens and in vitro binding studies, we found that this region coincides with a direct binding site for U2AF35, the small subunit of the splicing factor U2AF. This interaction is evolutionarily conserved across metazoa, indicating its significance. We further found in human cells that the exogenously expressed large U2AF subunit, U2AF65, accumulates in spliced mRNP, leading to the recruitment of U2AF35 and TAP. Similarly to TAP, U2AF65 stimulated directly the nuclear export and expression of an mRNA that is otherwise retained in the nucleus. Together with our finding that U2AF is continuously exported from the nucleus, these data suggest that U2AF participates in nuclear export, by facilitating TAP's addition to its mRNA substrates.
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Affiliation(s)
- Andrei S Zolotukhin
- Human Retrovirus Pathogenesis Section, Basic Research Laboratory, Center for Cancer Research, NCI, National Institutes of Health, Frederick, Maryland 21702-1201, USA
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44
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Chuong SDX, Mullen RT, Muench DG. Identification of a rice RNA- and microtubule-binding protein as the multifunctional protein, a peroxisomal enzyme involved in the beta -oxidation of fatty acids. J Biol Chem 2002; 277:2419-29. [PMID: 11706039 DOI: 10.1074/jbc.m109510200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The control of subcellular mRNA localization and translation is often mediated by protein factors that are directly or indirectly associated with the cytoskeleton. We report the identification and characterization of a rice seed protein that possesses both RNA and microtubule binding activities. In vitro UV cross-linking assays indicated that this protein binds to all mRNA sequences tested, although there was evidence for preferential binding to RNAs that contained A-C nucleotide sequence motifs. The protein was purified to homogeneity using a two-step procedure, and amino acid sequencing identified it as the multifunctional protein (MFP), a peroxisomal enzyme known to possess a number of activities involved in the beta-oxidation of fatty acids. The recombinant version of this rice MFP binds to RNA in UV cross-linking and gel mobility shift experiments, co-sediments specifically with microtubules, and possesses at least two enzymatic activities involved in peroxisomal fatty acid beta-oxidation. Taken together these data suggest that MFP has an important role in mRNA physiology in the cytoplasm, perhaps in regulating the localization or translation of mRNAs through an interaction with microtubules, in addition to its peroxisomal function.
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Affiliation(s)
- Simon D X Chuong
- Department of Biological Sciences, University of Calgary, Calgary, Alberta T2N 1N4, Canada
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45
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Kraemer D, Dresbach T, Drenckhahn D. Mrnp41 (Rae 1p) associates with microtubules in HeLa cells and in neurons. Eur J Cell Biol 2001; 80:733-40. [PMID: 11831386 DOI: 10.1078/0171-9335-00216] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Mrnp41 (hRae1p) is an evolutionarily highly conserved protein, which is a potential component of mRNP particles and plays a role in nuclear mRNA export. The protein is mainly localized at the nuclear pore complex, but is also associated with distinct nuclear domains and with a meshwork of numerous small particles in the cytoplasm (Kraemer and Blobel (1997): Proc. Natl. Acad. Sci. USA 91, 1519-1523). We show that the cytoplasmic pattern of mrnp41 is sensitive to treatment with the microtubule (MT)-depolymerizing drug nocodazole which causes disappearance of mrnp41 from the cell periphery and concentration around the nucleus. By immunofluorescence we demonstrate that mrnp41 colocalizes with MT in HeLa cells and displays an MT-like distribution in cultured neurons. Association of mrnp41 with MT is further demonstrated by copurification with MT from pig brain throughout several steps of polymerization and depolymerization. Separation of MT-associated proteins (MAPs) by phosphocellulose (PC) chromatography showed copurification of mrnp41 with MAPs. These data show an association of mrnp41 with MT and, moreover, demonstrate that an intact MT system is necessary for dispersion of mrnp41-containing particles to the cellular periphery. The essential role of mrnp41 in spindle pole separation and cell cycle progression may also be related to its ability to bind to MTs.
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Affiliation(s)
- D Kraemer
- Medizinische Poliklinik, Julius-Maximilians Universität, Würzburg, Germany.
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Dimaano C, Ball JR, Prunuske AJ, Ullman KS. RNA association defines a functionally conserved domain in the nuclear pore protein Nup153. J Biol Chem 2001; 276:45349-57. [PMID: 11567018 DOI: 10.1074/jbc.m102592200] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Traffic between the nucleus and cytoplasm takes place through a macromolecular structure termed the nuclear pore complex. To understand how the vital process of nucleocytoplasmic transport occurs, the contribution of individual pore proteins must be elucidated. One such protein, the nucleoporin Nup153, is localized to the nuclear basket of the pore complex and has been shown to be a central component of the nuclear transport machinery. Perturbation of Nup153 function was demonstrated previously to block the export of several classes of RNA cargo. Moreover, these studies also showed that Nup153 can stably associate with RNA in vitro. In this study, we have mapped a domain within Nup153, encompassing amino acids 250-400 in human Nup153, that is responsible for RNA association. After cloning this region of Xenopus Nup153, we performed a cross-species analysis. Despite variation in sequence conservation between Drosophila, Xenopus, and human, this domain of Nup153 displayed robust RNA binding activity in each case, indicating that this property is a hallmark feature of Nup153 and pointing toward a subset of amino acid residues that are key to conferring this ability. We have further determined that a recombinant fragment of Nup153 can bind directly to RNA and that this fragment can interact with endogenous RNA targets. Our findings identify a functionally conserved domain in Nup153 and suggest a role for RNA binding in Nup153 function at the nuclear pore.
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Affiliation(s)
- C Dimaano
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah 84112, USA
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Mili S, Shu HJ, Zhao Y, Piñol-Roma S. Distinct RNP complexes of shuttling hnRNP proteins with pre-mRNA and mRNA: candidate intermediates in formation and export of mRNA. Mol Cell Biol 2001; 21:7307-19. [PMID: 11585913 PMCID: PMC99905 DOI: 10.1128/mcb.21.21.7307-7319.2001] [Citation(s) in RCA: 129] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2001] [Accepted: 07/30/2001] [Indexed: 11/20/2022] Open
Abstract
Nascent pre-mRNAs associate with hnRNP proteins in hnRNP complexes, the natural substrates for mRNA processing. Several lines of evidence indicate that hnRNP complexes undergo substantial remodeling during mRNA formation and export. Here we report the isolation of three distinct types of pre-mRNP and mRNP complexes from HeLa cells associated with hnRNP A1, a shuttling hnRNP protein. Based on their RNA and protein compositions, these complexes are likely to represent distinct stages in the nucleocytoplasmic shuttling pathway of hnRNP A1 with its bound RNAs. In the cytoplasm, A1 is associated with its nuclear import receptor (transportin), the cytoplasmic poly(A)-binding protein, and mRNA. In the nucleus, A1 is found in two distinct types of complexes that are differently associated with nuclear structures. One class contains pre-mRNA and mRNA and is identical to previously described hnRNP complexes. The other class behaves as freely diffusible nuclear mRNPs (nmRNPs) at late nuclear stages of maturation and possibly associated with nuclear mRNA export. These nmRNPs differ from hnRNPs in that while they contain shuttling hnRNP proteins, the mRNA export factor REF, and mRNA, they do not contain nonshuttling hnRNP proteins or pre-mRNA. Importantly, nmRNPs also contain proteins not found in hnRNP complexes. These include the alternatively spliced isoforms D01 and D02 of the hnRNP D proteins, the E0 isoform of the hnRNP E proteins, and LRP130, a previously reported protein with unknown function that appears to have a novel type of RNA-binding domain. The characteristics of these complexes indicate that they result from RNP remodeling associated with mRNA maturation and delineate specific changes in RNP protein composition during formation and transport of mRNA in vivo.
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Affiliation(s)
- S Mili
- Department of Biochemistry and Molecular Biology, Mount Sinai School of Medicine, New York, New York 10029-6574, USA
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Marelli M, Dilworth DJ, Wozniak RW, Aitchison JD. The dynamics of karyopherin-mediated nuclear transport. Biochem Cell Biol 2001. [DOI: 10.1139/o01-149] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The regulated exchange of proteins and nucleic acids between the nucleus and cytoplasm demands a complex interplay between nuclear pore complexes (NPCs), which provide conduits in the nuclear envelope, and mobile transport receptors (or karyopherins, also known as importins/exportins) that bind and mediate the translocation of cargoes through the NPCs. Biochemical characterization of individual karyopherins has led to the identification of many of their cargoes and to the elucidation of the mechanisms by which they mediate transport. Likewise, the characterization of numerous NPC-associated components, in combination with structural studies of NPCs, have begun to address the possible mechanisms that drive nucleocytoplasmic transport, and the role that different nucleoporins play in the transport process. Some recent studies indicate that several NPC-associated factors, previously thought to be stable components of the NPC, dynamically interact with both nuclear and cytoplasmic aspects of the NPC. The mobility of these components challenges our conventional view of the NPC as the stationary phase of transport. These components and their potiential roles in nucleo-cytoplasmic transport are discussed.Key words: Nucleocytoplasmic transport, nuclear pore complex, nucleoporin, karyopherin, Nup2p.
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Abstract
Current models for the export of messenger RNA share the notion that the highly abundant class of nuclear RNA-binding proteins--the hnRNP proteins--have a key role in exporting RNA. But recent studies have led to a new understanding of several non-hnRNP proteins, including SR proteins and the conserved mRNA export factor ALY, which are recruited to the mRNA during pre-mRNA splicing. These studies, together with older work on hnRNP particles and assembly of the spliceosome, lead us to a new view of mRNA export. In our model, the non-hnRNP factors form a splicing-dependent mRNP complex that specifically targets mature mRNA for export, while hnRNP proteins retain introns in the nucleus. A machinery that is conserved between yeast and higher eukaryotes functions to export the mRNA.
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Affiliation(s)
- R Reed
- Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue, Boston, MA 02115, USA.
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Zenklusen D, Vinciguerra P, Strahm Y, Stutz F. The yeast hnRNP-Like proteins Yra1p and Yra2p participate in mRNA export through interaction with Mex67p. Mol Cell Biol 2001; 21:4219-32. [PMID: 11390651 PMCID: PMC87083 DOI: 10.1128/mcb.21.13.4219-4232.2001] [Citation(s) in RCA: 122] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Yra1p is an essential nuclear protein which belongs to the evolutionarily conserved REF (RNA and export factor binding proteins) family of hnRNP-like proteins. Yra1p contributes to mRNA export in vivo and directly interacts with RNA and the shuttling mRNP export receptor Mex67p in vitro. Here we describe a second nonessential Saccharomyces cerevisiae family member, called Yra2p, which is able to complement a YRA1 deletion when overexpressed. Like other REF proteins, Yra1p and Yra2p consist of two highly conserved N- and C-terminal boxes and a central RNP-like RNA-binding domain (RBD). These conserved regions are separated by two more variable regions, N-vr and C-vr. Surprisingly, the deletion of a single conserved box or the deletion of the RBD in Yra1p does not affect viability. Consistently, neither the conserved N and C boxes nor the RBD is required for Mex67p and RNA binding in vitro. Instead, the N-vr and C-vr regions both interact with Mex67p and RNA. We further show that Yra1 deletion mutants which poorly interact with Mex67p in vitro affect the association of Mex67p with mRNP complexes in vivo and are paralleled by poly(A)(+) RNA export defects. These observations support the idea that Yra1p promotes mRNA export by facilitating the recruitment of Mex67p to the mRNP.
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Affiliation(s)
- D Zenklusen
- Institute of Microbiology, Centre Hospitalier Universitaire Vaudois, 1012 Lausanne, Switzerland
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