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Li Z, Chen S, Zhao L, Huang G, Xu H, Yang X, Wang P, Gao N, Sui SF. Nuclear export of pre-60S particles through the nuclear pore complex. Nature 2023:10.1038/s41586-023-06128-y. [PMID: 37258668 DOI: 10.1038/s41586-023-06128-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2022] [Accepted: 04/25/2023] [Indexed: 06/02/2023]
Abstract
The nuclear pore complex (NPC) is the bidirectional gate that mediates the exchange of macromolecules or their assemblies between nucleus and cytoplasm1-3. The assembly intermediates of the ribosomal subunits, pre-60S and pre-40S particles, are among the largest cargoes of the NPC and the export of these gigantic ribonucleoproteins requires numerous export factors4,5. Here we report the cryo-electron microscopy structure of native pre-60S particles trapped in the channel of yeast NPCs. In addition to known assembly factors, multiple factors with export functions are also included in the structure. These factors in general bind to either the flexible regions or subunit interface of the pre-60S particle, and virtually form many anchor sites for NPC binding. Through interactions with phenylalanine-glycine (FG) repeats from various nucleoporins of NPC, these factors collectively facilitate the passage of the pre-60S particle through the central FG repeat network of the NPC. Moreover, in silico analysis of the axial and radial distribution of pre-60S particles within the NPC shows that a single NPC can take up to four pre-60S particles simultaneously, and pre-60S particles are enriched in the inner ring regions close to the wall of the NPC with the solvent-exposed surface facing the centre of the nuclear pore. Our data suggest a translocation model for the export of pre-60S particles through the NPC.
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Affiliation(s)
- Zongqiang Li
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, School of Life Sciences, Tsinghua University, Beijing, China
| | - Shuaijiabin Chen
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, School of Life Sciences, Tsinghua University, Beijing, China
| | - Liang Zhao
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, School of Life Sciences, Tsinghua University, Beijing, China
| | - Guoqiang Huang
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, School of Life Sciences, Tsinghua University, Beijing, China
| | - Huiqin Xu
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
| | - Xiaoyun Yang
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China
| | - Peiyi Wang
- Cryo-EM Center, Southern University of Science and Technology, Shenzhen, China
| | - Ning Gao
- State Key Laboratory of Membrane Biology, Peking-Tsinghua Joint Center for Life Sciences, School of Life Sciences, Peking University, Beijing, China
| | - Sen-Fang Sui
- School of Life Sciences, Southern University of Science and Technology, Shenzhen, China.
- State Key Laboratory of Membrane Biology, Beijing Advanced Innovation Center for Structural Biology, Beijing Frontier Research Center for Biological Structure, School of Life Sciences, Tsinghua University, Beijing, China.
- Cryo-EM Center, Southern University of Science and Technology, Shenzhen, China.
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Impact of oral lipid and glucose tolerance tests on the postprandial concentrations of angiopoietin-like proteins (Angptl) 3 and 4. Eur J Nutr 2021; 61:1919-1929. [PMID: 34951653 PMCID: PMC9106616 DOI: 10.1007/s00394-021-02748-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 11/16/2021] [Indexed: 11/22/2022]
Abstract
Background The postprandial regulation of angiopoietin-like proteins (Angptls) and their expression in adipocytes is poorly characterized. Objective Circulating Angptl3 and 4 were analyzed in healthy individuals undergoing either an oral lipid tolerance test (OLTT; n = 98) or an oral glucose tolerance test (OGTT; n = 99). Venous blood was drawn after 0, 2, 4, and 6 h during OLTT and after 0, 1, and 2 h during OGTT. Anthropometric and laboratory parameters were assessed and concentrations of Angptls were quantified by enzyme-linked immunosorbent assay. Angptl gene expression in 3T3-L1 adipocytes and in murine adipose tissues and cellular fractions was analyzed by quantitative real-time PCR. Results Angptl3 concentrations significantly decreased while Angptl4 levels continuously increased during OLTT. Both proteins remained unaffected during OGTT. Angptl3 and Angptl4 were expressed in murine subcutaneous and visceral AT with higher mRNA levels in mature adipocytes when compared to the stroma-vascular cell fraction. Both proteins were strongly induced during 3T3-L1 adipocyte differentiation and they were unresponsive to glucose in mature fat cells. Adipocyte Angptl3 (but not Angptl4) mRNA expression was inhibited by the polyunsaturated fatty acids arachidonic acid and docosahexaenoic acid, whereas nine types of dietary fatty acids remained without any effect. Conclusions There is evidence of short-time regulation of Angptl3/4 levels upon metabolic stress. Angptl4 expression is high and Angptl3 expression is low in AT and restricted mainly to mature adipocytes without any differences concerning fat compartments. Whereas dietary fatty acids and glucose are without any effect, omega-3/-6-polyunsaturated fatty acids inhibited Anptl3 expression in adipocytes.
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Lee ES, Wolf EJ, Ihn SSJ, Smith HW, Emili A, Palazzo AF. TPR is required for the efficient nuclear export of mRNAs and lncRNAs from short and intron-poor genes. Nucleic Acids Res 2021; 48:11645-11663. [PMID: 33091126 PMCID: PMC7672458 DOI: 10.1093/nar/gkaa919] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2019] [Revised: 09/21/2020] [Accepted: 10/02/2020] [Indexed: 12/14/2022] Open
Abstract
While splicing has been shown to enhance nuclear export, it has remained unclear whether mRNAs generated from intronless genes use specific machinery to promote their export. Here, we investigate the role of the major nuclear pore basket protein, TPR, in regulating mRNA and lncRNA nuclear export in human cells. By sequencing mRNA from the nucleus and cytosol of control and TPR-depleted cells, we provide evidence that TPR is required for the efficient nuclear export of mRNAs and lncRNAs that are generated from short transcripts that tend to have few introns, and we validate this with reporter constructs. Moreover, in TPR-depleted cells reporter mRNAs generated from short transcripts accumulate in nuclear speckles and are bound to Nxf1. These observations suggest that TPR acts downstream of Nxf1 recruitment and may allow mRNAs to leave nuclear speckles and properly dock with the nuclear pore. In summary, our study provides one of the first examples of a factor that is specifically required for the nuclear export of intronless and intron-poor mRNAs and lncRNAs.
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Affiliation(s)
- Eliza S Lee
- University of Toronto, Department of Biochemistry, Canada
| | - Eric J Wolf
- University of Toronto, Department of Molecular Genetics, Canada
| | - Sean S J Ihn
- University of Toronto, Department of Biochemistry, Canada
| | | | - Andrew Emili
- University of Toronto, Department of Molecular Genetics, Canada.,Boston University School of Medicine, Department of Biochemistry, Boston, MA, USA
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4
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Gallardo P, Real-Calderón P, Flor-Parra I, Salas-Pino S, Daga RR. Acute Heat Stress Leads to Reversible Aggregation of Nuclear Proteins into Nucleolar Rings in Fission Yeast. Cell Rep 2020; 33:108377. [DOI: 10.1016/j.celrep.2020.108377] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2020] [Revised: 08/24/2020] [Accepted: 10/21/2020] [Indexed: 12/15/2022] Open
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Satoh R, Hagihara K, Sugiura R. Rae1-mediated nuclear export of Rnc1 is an important determinant in controlling MAPK signaling. Curr Genet 2017; 64:103-108. [PMID: 28799069 DOI: 10.1007/s00294-017-0732-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2017] [Revised: 08/08/2017] [Accepted: 08/08/2017] [Indexed: 01/24/2023]
Abstract
In eukaryotic cells, RNA binding proteins (RBPs) play critical roles in regulating almost every aspect of gene expression, often shuttling between the nucleus and the cytoplasm. They are also key determinants in cell fate via controlling the target mRNAs under the regulation of various signaling pathways in response to environmental stresses. Therefore, understanding the mechanisms that couple the location of mRNA and RBPs is a major challenge in the field of gene expression and signal responses. In fission yeast, a KH-type RBP Rnc1 negatively regulates MAPK signaling activation via mRNA stabilization of the dual-specificity MAPK phosphatase Pmp1, which dephosphorylates MAPK Pmk1. Rnc1 also serves as a target of MAPK phosphorylation, which makes a feedback loop mediated by an RBP. We recently discovered that the nuclear export of Rnc1 requires mRNA-binding ability and the mRNA export factor Rae1. This strongly suggested the presence of an mRNA-export system, which recognizes the mRNA/RBP complex and dictates the location and post-transcriptional regulation of mRNA cargo. Here, we briefly review the known mechanisms of general nuclear transporting systems, with an emphasis on our recent findings on the spatial regulation of Rnc1 and its impact on the regulation of the MAPK signal transduction cascade.
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Affiliation(s)
- Ryosuke Satoh
- 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
| | - Reiko Sugiura
- Laboratory of Molecular Pharmacogenomics, Department of Pharmaceutical Sciences, Kindai University, Higashiosaka City, Osaka, 577-8502, Japan.
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6
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Zander G, Kramer W, Seel A, Krebber H. Saccharomyces cerevisiae Gle2/Rae1 is involved in septin organization, essential for cell cycle progression. Yeast 2017; 34:459-470. [PMID: 28776765 PMCID: PMC6472880 DOI: 10.1002/yea.3249] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Revised: 06/29/2017] [Accepted: 07/28/2017] [Indexed: 01/22/2023] Open
Abstract
Gle2/Rae1 is highly conserved from yeast to humans and has been described as an mRNA export factor. Additionally, it is implicated in the anaphase-promoting complex-mediated cell cycle regulation in higher eukaryotes. Here we identify an involvement for Saccharomyces cerevisiae Gle2 in septin organization, which is crucial for cell cycle progression and cell division. Gle2 genetically and physically interacts with components of the septin ring. Importantly, deletion of GLE2 leads to elongated buds, severe defects in septin-assembly and their cellular mislocalization. Septin-ring formation is triggered by the septin-regulating GTPase Cdc42, which establishes and maintains cell polarity. Additionally, activity of the master cell cycle regulator Cdc28 (Cdk1) is needed, which is, besides other functions, also required for G2 /M-transition, and in yeast particularly responsible for initiating the apical-isotropic switch. We show genetic and physical interactions of Gle2 with both Cdc42 and Cdc28. Most importantly, we find that gle2∆ severely mislocalizes Cdc42, leading to defects in septin-complex formation and cell division. Thus, our findings suggest that Gle2 participates in the efficient organization of the septin assembly network, where it might act as a scaffold protein. © 2017 The Authors. Yeast published by John Wiley & Sons, Ltd.
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Affiliation(s)
- Gesa Zander
- Abteilung für Molekulare Genetik, Institut für Mikrobiologie und Genetik, Göttinger Zentrum für Molekulare Biowissenschaften, Georg-August Universität Göttingen, Göttingen, Germany
| | - Wilfried Kramer
- Abteilung für Molekulare Genetik, Institut für Mikrobiologie und Genetik, Göttinger Zentrum für Molekulare Biowissenschaften, Georg-August Universität Göttingen, Göttingen, Germany
| | - Anika Seel
- Abteilung für Molekulare Genetik, Institut für Mikrobiologie und Genetik, Göttinger Zentrum für Molekulare Biowissenschaften, Georg-August Universität Göttingen, Göttingen, Germany
| | - Heike Krebber
- Abteilung für Molekulare Genetik, Institut für Mikrobiologie und Genetik, Göttinger Zentrum für Molekulare Biowissenschaften, Georg-August Universität Göttingen, Göttingen, Germany
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7
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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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8
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RNA Export through the NPC in Eukaryotes. Genes (Basel) 2015; 6:124-49. [PMID: 25802992 PMCID: PMC4377836 DOI: 10.3390/genes6010124] [Citation(s) in RCA: 81] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2014] [Revised: 02/27/2015] [Accepted: 03/10/2015] [Indexed: 02/08/2023] Open
Abstract
In eukaryotic cells, RNAs are transcribed in the nucleus and exported to the cytoplasm through the nuclear pore complex. The RNA molecules that are exported from the nucleus into the cytoplasm include messenger RNAs (mRNAs), ribosomal RNAs (rRNAs), transfer RNAs (tRNAs), small nuclear RNAs (snRNAs), micro RNAs (miRNAs), and viral mRNAs. Each RNA is transported by a specific nuclear export receptor. It is believed that most of the mRNAs are exported by Nxf1 (Mex67 in yeast), whereas rRNAs, snRNAs, and a certain subset of mRNAs are exported in a Crm1/Xpo1-dependent manner. tRNAs and miRNAs are exported by Xpot and Xpo5. However, multiple export receptors are involved in the export of some RNAs, such as 60S ribosomal subunit. In addition to these export receptors, some adapter proteins are required to export RNAs. The RNA export system of eukaryotic cells is also used by several types of RNA virus that depend on the machineries of the host cell in the nucleus for replication of their genome, therefore this review describes the RNA export system of two representative viruses. We also discuss the NPC anchoring-dependent mRNA export factors that directly recruit specific genes to the NPC.
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Cho YS, Jang S, Yoon JH. Isolation of a novel rmn1 gene genetically linked to spnab2 with respect to mRNA export in fission yeast. Mol Cells 2012; 34:315-21. [PMID: 22936388 PMCID: PMC3887835 DOI: 10.1007/s10059-012-0157-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Revised: 07/05/2012] [Accepted: 07/06/2012] [Indexed: 10/28/2022] Open
Abstract
In fission yeast, Schizosaccharomyces pombe, the spnab2 gene encodes an ortholog of the budding yeast nuclear abundant poly(A)(+) RNA-binding protein 2 (Nab2) that is an essential protein required for both mRNA biogenesis and nuclear export of mRNA to the cytoplasm. We have previously isolated three mutants (SLnab1-3) that showed synthetic lethality under the repressed condition of spnab2 expression. In this study, we isolated a novel rmn1 gene as a multicopy suppressor that complemented the defects in growth and mRNA export of SLnab1 mutant cells. The rmn1 gene contained three introns and encoded a 589 amino-acid protein with the RNA recognition motif (RRM) in the central region. The Δrmn1 null mutant was viable but showed a s light mRNA export defect. However, its over-expression caused a deleterious effect on growth accompanied by intense accumulation of poly(A)(+) RNA in the nucleus. The combination of Δrmn1 with Δspnab2 or Δspmex67 also inhibited growth. In addition, Rmn1p was associated with Rae1p in vivo. These results suggest that rmn1 is a novel gene that is functionally linked to spnab2.
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Affiliation(s)
- Ye-Seul Cho
- School of Biological Sciences and Chemistry, and Basic Sciences Research Institute, Sungshin Women’s University, Seoul 142-732,
Korea
| | - Sooyeon Jang
- School of Biological Sciences and Chemistry, and Basic Sciences Research Institute, Sungshin Women’s University, Seoul 142-732,
Korea
| | - Jin Ho Yoon
- School of Biological Sciences and Chemistry, and Basic Sciences Research Institute, Sungshin Women’s University, Seoul 142-732,
Korea
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10
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Tange Y, Kurabayashi A, Goto B, Hoe KL, Kim DU, Park HO, Hayles J, Chikashige Y, Tsutumi C, Hiraoka Y, Yamao F, Nurse P, Niwa O. The CCR4-NOT complex is implicated in the viability of aneuploid yeasts. PLoS Genet 2012; 8:e1002776. [PMID: 22737087 PMCID: PMC3380822 DOI: 10.1371/journal.pgen.1002776] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Accepted: 05/05/2012] [Indexed: 12/23/2022] Open
Abstract
To identify the genes required to sustain aneuploid viability, we screened a deletion library of non-essential genes in the fission yeast Schizosaccharomyces pombe, in which most types of aneuploidy are eventually lethal to the cell. Aneuploids remain viable for a period of time and can form colonies by reducing the extent of the aneuploidy. We hypothesized that a reduction in colony formation efficiency could be used to screen for gene deletions that compromise aneuploid viability. Deletion mutants were used to measure the effects on the viability of spores derived from triploid meiosis and from a chromosome instability mutant. We found that the CCR4-NOT complex, an evolutionarily conserved general regulator of mRNA turnover, and other related factors, including poly(A)-specific nuclease for mRNA decay, are involved in aneuploid viability. Defective mutations in CCR4-NOT complex components in the distantly related yeast Saccharomyces cerevisiae also affected the viability of spores produced from triploid cells, suggesting that this complex has a conserved role in aneuploids. In addition, our findings suggest that the genes required for homologous recombination repair are important for aneuploid viability.
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Affiliation(s)
- Yoshie Tange
- Kazusa DNA Research Institute, Kisarazu, Chiba, Japan
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
| | | | - Bunshiro Goto
- Kazusa DNA Research Institute, Kisarazu, Chiba, Japan
| | - Kwang-Lae Hoe
- Chungnam National University, Graduate School of New Drug Discovery and Development, Yusong-gu, Daejeon, Korea
| | - Dong-Uk Kim
- Aging Research Center, Korea Research Institute of Bioscience and Biotechnology (KRIBB), Yusong-gu, Daejeon, Korea
| | | | - Jacqueline Hayles
- Cancer Research UK, The London Research Institute, London, United Kingdom
| | - Yuji Chikashige
- National Institute of Information and Communications Technology, Kobe, Japan
| | - Chihiro Tsutumi
- National Institute of Information and Communications Technology, Kobe, Japan
| | - Yasushi Hiraoka
- Graduate School of Frontier Biosciences, Osaka University, Suita, Osaka, Japan
- National Institute of Information and Communications Technology, Kobe, Japan
| | - Fumiaki Yamao
- National Institute of Genetics, Mishima, Shizuoka, Japan
| | - Paul Nurse
- Cancer Research UK, The London Research Institute, London, United Kingdom
- The Rockefeller University, New York, New York, United States of America
| | - Osami Niwa
- Kazusa DNA Research Institute, Kisarazu, Chiba, Japan
- The Rockefeller University, New York, New York, United States of America
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12
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Characterization of the ptr5+ gene involved in nuclear mRNA export in fission yeast. Biochem Biophys Res Commun 2012; 418:62-6. [PMID: 22240020 DOI: 10.1016/j.bbrc.2011.12.128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Accepted: 12/26/2011] [Indexed: 11/23/2022]
Abstract
To analyze the mechanisms of mRNA export from the nucleus to the cytoplasm, we have isolated eleven mutants, ptr [poly(A)(+) RNA transport] 1 to 11, which accumulate poly(A)(+) RNA in the nucleus at a nonpermissive temperature in Schizosaccharomyces pombe. Of those, the ptr5-1 mutant shows dots- or a ring-like accumulation of poly(A)(+) RNA at the nuclear periphery after shifting to the nonpermissive temperature. We cloned the ptr5(+) gene and found that it encodes a component of the nuclear pore complex (NPC), nucleoporin 85 (Nup85). The ptr5-1 mutant shows no defects in protein transport, suggesting the specific involvement of Ptr5p/Nup85p in nuclear mRNA export in S. pombe. We identified Seh1p, a nucleoporin interacting with Nup85p, an mRNA-binding protein Mlo3p, and Sac3p, a component of the TREX-2 complex involved in coupling of nuclear mRNA export with transcription, as multi-copy suppressors for the ptr5-1 mutation. In addition, we found that the ptr5-1 mutation is synthetically lethal with a mutation of the mRNA export factor Rae1p, and that the double mutant exaggerates defective nuclear mRNA export, suggesting that Ptr5p/Nup85p is involved in nuclear mRNA export through Rae1p. Interestingly, the ptr5-1 mutation also showed synthetic effects with several prp pre-mRNA splicing mutations, suggesting a functional linkage between the NPCs and the splicing apparatus in the yeast nucleus.
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Nuclear export as a key arbiter of "mRNA identity" in eukaryotes. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2012; 1819:566-77. [PMID: 22248619 DOI: 10.1016/j.bbagrm.2011.12.012] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/04/2011] [Revised: 12/23/2011] [Accepted: 12/29/2011] [Indexed: 01/15/2023]
Abstract
Over the past decade, various studies have indicated that most of the eukaryotic genome is transcribed at some level. The pervasiveness of transcription might seem surprising when one considers that only a quarter of the human genome comprises genes (including exons and introns) and less than 2% codes for protein. This conundrum is partially explained by the unique evolutionary pressures that are imposed on species with small population sizes, such as eukaryotes. These conditions promote the expansion of introns and non-functional intergenic DNA, and the accumulation of cryptic transcriptional start sites. As a result, the eukaryotic gene expression machinery must effectively evaluate whether or not a transcript has all the hallmarks of a protein-coding mRNA. If a transcript contains these features, then positive feedback loops are activated to further stimulate its transcription, processing, nuclear export and ultimately, translation. However if a transcript lacks features associated with "mRNA identity", then the RNA is degraded and/or used to inhibit further transcription and translation of the gene. Here we discuss how mRNA identity is assessed by the nuclear export machinery in order to extract meaningful information from the eukaryotic genome. In the process, we provide an explanation of why certain sequences that are enriched in protein-coding genes, such as the signal sequence coding region, promote mRNA nuclear export in vertebrates. This article is part of a Special Issue entitled: Nuclear Transport and RNA Processing.
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14
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Zhang ZC, Satterly N, Fontoura BMA, Chook YM. Evolutionary development of redundant nuclear localization signals in the mRNA export factor NXF1. Mol Biol Cell 2011; 22:4657-68. [PMID: 21965294 PMCID: PMC3226482 DOI: 10.1091/mbc.e11-03-0222] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Unexpected redundancy in the nuclear import pathways used by the essential mRNA export factor NXF1 increases progressively from fungi to nematodes and insects to chordates, potentially paralleling the increasing complexity in mRNA export regulation and the evolution of new nuclear functions for NXF1. In human cells, the mRNA export factor NXF1 resides in the nucleoplasm and at nuclear pore complexes. Karyopherin β2 or transportin recognizes a proline–tyrosine nuclear localization signal (PY-NLS) in the N-terminal tail of NXF1 and imports it into the nucleus. Here biochemical and cellular studies to understand the energetic organization of the NXF1 PY-NLS reveal unexpected redundancy in the nuclear import pathways used by NXF1. Human NXF1 can be imported via importin β, karyopherin β2, importin 4, importin 11, and importin α. Two NLS epitopes within the N-terminal tail, an N-terminal basic segment and a C-terminal R-X2-5-P-Y motif, provide the majority of binding energy for all five karyopherins. Mutation of both NLS epitopes abolishes binding to the karyopherins, mislocalized NXF1 to the cytoplasm, and significantly compromised its mRNA export function. The understanding of how different karyopherins recognize human NXF1, the examination of NXF1 sequences from divergent eukaryotes, and the interactions of NXF1 homologues with various karyopherins reveals the evolutionary development of redundant NLSs in NXF1 of higher eukaryotes. Redundancy of nuclear import pathways for NXF1 increases progressively from fungi to nematodes and insects to chordates, potentially paralleling the increasing complexity in mRNA export regulation and the evolution of new nuclear functions for NXF1.
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Affiliation(s)
- Zi Chao Zhang
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390-9041, USA
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15
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Thomas M, Lischka P, Müller R, Stamminger T. The cellular DExD/H-box RNA-helicases UAP56 and URH49 exhibit a CRM1-independent nucleocytoplasmic shuttling activity. PLoS One 2011; 6:e22671. [PMID: 21799930 PMCID: PMC3142171 DOI: 10.1371/journal.pone.0022671] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Accepted: 07/03/2011] [Indexed: 01/26/2023] Open
Abstract
Cellular DExD/H-box RNA-helicases perform essential functions during mRNA biogenesis. The closely related human proteins UAP56 and URH49 are members of this protein family and play an essential role for cellular mRNA export by recruiting the adaptor protein REF to spliced and unspliced mRNAs. In order to gain insight into their mode of action, we aimed to characterize these RNA-helicases in more detail. Here, we demonstrate that UAP56 and URH49 exhibit an intrinsic CRM1-independent nucleocytoplasmic shuttling activity. Extensive mapping studies identified distinct regions within UAP56 or URH49 required for (i) intranuclear localization (UAP56 aa81-381) and (ii) interaction with REF (UAP56 aa51-428). Moreover, the region conferring nucleocytoplasmic shuttling activity was mapped to the C-terminus of UAP56, comprising the amino acids 195-428. Interestingly, this region coincides with a domain within Uap56p of S. pombe that has been reported to be required for both Rae1p-interaction and nucleocytoplasmic shuttling. However, in contrast to this finding we report that human UAP56 shuttles independently from Rae1. In summary, our results reveal nucleocytoplasmic shuttling as a conserved feature of yeast and human UAP56, while their export receptor seems to have diverged during evolution.
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Affiliation(s)
- Marco Thomas
- Institute for Clinical and Molecular Virology, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Peter Lischka
- Institute for Clinical and Molecular Virology, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Regina Müller
- Institute for Clinical and Molecular Virology, University of Erlangen-Nuremberg, Erlangen, Germany
| | - Thomas Stamminger
- Institute for Clinical and Molecular Virology, University of Erlangen-Nuremberg, Erlangen, Germany
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16
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Moon D, Park YS, Kim CY, Yoon JH. Isolation of synthetic lethal mutations in the rsm1-null mutant of fission yeast. J Microbiol 2010; 48:701-5. [PMID: 21046351 DOI: 10.1007/s12275-010-0353-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2010] [Accepted: 09/27/2010] [Indexed: 11/30/2022]
Abstract
To identify mutations in genes that are genetically linked to rsm1, we performed a synthetic lethal genetic screen in the fission yeast, Schizosaccharomyces pombe. Four mutations that showed synthetic lethality in combination with the rsm1null allele were isolated from approximately 320,000 colonies and defined in three complementation groups. One mutant (SLrsm1) exhibited a significant accumulation of poly(A)(+) RNA in the nucleus under synthetic lethal conditions, while the rest had no mRNA export defects. In addition, some genes (spmex67, rae1, or mlo3) required for mRNA export complemented the growth defects of the identified mutants. These results suggest that the isolated mutants contain mutations in genes that are involved in mRNA export and/or pre-mRNA retention.
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Affiliation(s)
- DongGeRaMi Moon
- School of Biological Sciences and Chemistry, Sungshin Women's University, Seoul 136-742, Republic of Korea
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17
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Selvanathan SP, Thakurta AG, Dhakshnamoorthy J, Zhou M, Veenstra TD, Dhar R. Schizosaccharomyces pombe Dss1p is a DNA damage checkpoint protein that recruits Rad24p, Cdc25p, and Rae1p to DNA double-strand breaks. J Biol Chem 2010; 285:14122-33. [PMID: 20231270 DOI: 10.1074/jbc.m109.083485] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Schizosaccharomyces pombe Dss1p and its homologs function in multiple cellular processes including recombinational repair of DNA and nuclear export of messenger RNA. We found that Tap-tagged Rad24p, a member of the 14-3-3 class of proteins, co-purified Dss1p along with mitotic activator Cdc25p, messenger RNA export/cell cycle factor Rae1p, 19 S proteasomal factors, and recombination protein Rhp51p (a Rad51p homolog). Using chromatin immunoprecipitation, we found that Dss1p recruited Rad24p and Rae1p to the double-strand break (DSB) sites. Furthermore, Cdc25p also recruited to the DSB site, and its recruitment was dependent on Dss1p, Rad24p, and the protein kinase Chk1p. Following DSB, all nuclear Cdc25p was found to be chromatin-associated. We found that Dss1p and Rae1p have a DNA damage checkpoint function, and upon treatment with UV light Deltadss1 cells entered mitosis prematurely with indistinguishable timing from Deltarad24 cells. Taken together, these results suggest that Dss1p plays a critical role in linking repair and checkpoint factors to damaged DNA sites by specifically recruiting Rad24p and Cdc25p to the DSBs. We suggest that the sequestration of Cdc25p to DNA damage sites could provide a mechanism for S. pombe cells to arrest at G(2)/M boundary in response to DNA damage.
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Affiliation(s)
- Saravana P Selvanathan
- Basic Research Laboratory, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, MD 20892, USA
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18
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Affiliation(s)
- Sean R Carmody
- Department of Cell and Developmental Biology, Vanderbilt University School of Medicine, Nashville, TN 38232, USA
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19
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Bae JA, Moon D, Yoon JH. Nup211, the fission yeast homolog of Mlp1/Tpr, is involved in mRNA export. J Microbiol 2009; 47:337-43. [PMID: 19557351 DOI: 10.1007/s12275-009-0125-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2009] [Accepted: 05/25/2009] [Indexed: 12/27/2022]
Abstract
Synthetic lethal mutants have been previously isolated in fission yeast Schizosaccharomyces pombe, which genetically interact with spmex67, in order to identify the genes involved in mRNA export. The nup211 gene was isolated by complementation of the growth defect in one of the synthetic lethal mutants, SLMex2, under synthetic lethal condition. We showed that Nup211, fission yeast homolog of Mlpl/Mlp2/Tpr, is essential for vegetative growth and Nup211-GFP proteins expressed at endogenous level are localized mainly in nuclear periphery. The accumulation of poly(A)(+) RNA in the nucleus is exhibited when expression of nup211 is repressed or over-expressed. These results suggest that the Nup211 protein plays a pivotal role of mRNA export in fission yeast.
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Affiliation(s)
- Jin-Ah Bae
- Department of Education, Sungshin Women's University, Seoul 136-742, Republic of Korea
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20
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Dual functions for the Schizosaccharomyces pombe inositol kinase Ipk1 in nuclear mRNA export and polarized cell growth. EUKARYOTIC CELL 2008; 8:134-46. [PMID: 19047361 DOI: 10.1128/ec.00279-08] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The inositol 1,3,4,5,6-pentakisphosphate (IP(5)) 2-kinase (Ipk1) catalyzes the production of inositol hexakisphosphate (IP(6)) in eukaryotic cells. Previous studies have shown that IP(6) is required for efficient nuclear mRNA export in the budding yeast Saccharomyces cerevisiae. Here, we report the first functional analysis of ipk1(+) in Schizosaccharomyces pombe. S. pombe Ipk1 (SpIpk1) is unique among Ipk1 orthologues in that it harbors a novel amino (N)-terminal domain with coiled-coil structural motifs similar to those of BAR (Bin-amphiphysin-Rvs) domain proteins. Mutants with ipk1(+) deleted (ipk1Delta) had mRNA export defects as well as pleiotropic defects in polarized growth, cell morphology, endocytosis, and cell separation. The SpIpk1 catalytic carboxy-terminal domain was required to rescue these defects, and the mRNA export block was genetically linked to SpDbp5 function and, likely, IP(6) production. However, the overexpression of the N-terminal domain alone also inhibited these functions in wild-type cells. This revealed a distinct noncatalytic function for the N-terminal domain. To test for connections with other inositol polyphosphates, we also analyzed whether the loss of asp1(+) function, encoding an IP(6) kinase downstream of Ipk1, had an effect on ipk1Delta cells. The asp1Delta mutant alone did not block mRNA export, and its cell morphology, polarized growth, and endocytosis defects were less severe than those of ipk1Delta cells. Moreover, ipk1Delta asp1Delta double mutants had altered inositol polyphosphate levels distinct from those of the ipk1Delta mutant. This suggested novel roles for asp1(+) upstream of ipk1(+). We propose that IP(6) production is a key signaling linchpin for regulating multiple essential cellular processes.
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21
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Moon D, Bae JA, Cho HJ, Yoon JH. The fission yeast homologue of Glel is essential for growth and involved in mRNA export. J Microbiol 2008; 46:422-8. [PMID: 18758733 DOI: 10.1007/s12275-008-0177-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2008] [Accepted: 07/22/2008] [Indexed: 12/16/2022]
Abstract
We have isolated Glel homologue (named as spglel) as a partial multicopy suppressor of the synthetic lethality of rael-167 elfl-21 in fission yeast Schizosaccharomyces pombe. The spglel is also able to complement partially temperature-sensitive phenotype of rael-167 only at a lower restrictive temperature. The spglel gene contains one intron and encodes a 480 amino-acid protein with predicted molecular weight of 56.2 kDa. We showed that spglel gene is essential for vegetative growth and functional Glel-GFP protein is localized mainly in NPC. The accumulation of poly(A)(+) RNA in the nucleus is exhibited when expression of spglel is repressed or over-expressed. These results suggest that the spGle1 protein is also involved in mRNA export in fission yeast.
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Affiliation(s)
- DongGeRaMi Moon
- Department of Biology, Institute of Basic Sciences, Seoul 136-742, Republic of Korea
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22
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Palazzo AF, Springer M, Shibata Y, Lee CS, Dias AP, Rapoport TA. The signal sequence coding region promotes nuclear export of mRNA. PLoS Biol 2008; 5:e322. [PMID: 18052610 PMCID: PMC2100149 DOI: 10.1371/journal.pbio.0050322] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2007] [Accepted: 10/19/2007] [Indexed: 11/19/2022] Open
Abstract
In eukaryotic cells, most mRNAs are exported from the nucleus by the transcription export (TREX) complex, which is loaded onto mRNAs after their splicing and capping. We have studied in mammalian cells the nuclear export of mRNAs that code for secretory proteins, which are targeted to the endoplasmic reticulum membrane by hydrophobic signal sequences. The mRNAs were injected into the nucleus or synthesized from injected or transfected DNA, and their export was followed by fluorescent in situ hybridization. We made the surprising observation that the signal sequence coding region (SSCR) can serve as a nuclear export signal of an mRNA that lacks an intron or functional cap. Even the export of an intron-containing natural mRNA was enhanced by its SSCR. Like conventional export, the SSCR-dependent pathway required the factor TAP, but depletion of the TREX components had only moderate effects. The SSCR export signal appears to be characterized in vertebrates by a low content of adenines, as demonstrated by genome-wide sequence analysis and by the inhibitory effect of silent adenine mutations in SSCRs. The discovery of an SSCR-mediated pathway explains the previously noted amino acid bias in signal sequences and suggests a link between nuclear export and membrane targeting of mRNAs. In eukaryotic cells, precursors of messenger RNAs (mRNAs) are synthesized and processed in the nucleus. During processing, noncoding introns are spliced out, and a cap and poly-adenosine sequence are added to the beginning and end of the transcript, respectively. The resulting mature mRNA is exported from the nucleus to the cytoplasm by crossing the nuclear pore. Both the introns and the cap help to recruit factors that are necessary for nuclear export of an mRNA. Here we provide evidence for a novel mRNA export pathway that is specific for transcripts coding for secretory proteins. These proteins contain signal sequences that target them for translocation across the endoplasmic reticulum membrane. We made the surprising observation that the signal sequence coding region (SSCR) can serve as a nuclear export signal of an mRNA that lacks an intron or functional cap. Even the export of an intron-containing natural mRNA was enhanced by its SSCR. The SSCR export signal appears to be characterized in vertebrates by a low content of adenines. Our discovery of an SSCR-mediated pathway explains the previously noted amino acid bias in signal sequences, and suggests a link between nuclear export and membrane targeting of mRNAs. Signal sequences, which target newly synthesized secretory proteins to the endoplasmic reticulum, are encoded by adenine-depleted nucleotide sequences that promote the nuclear export of the mRNAs.
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Affiliation(s)
- Alexander F Palazzo
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Michael Springer
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Yoko Shibata
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Chung-Sheng Lee
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Anusha P Dias
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Tom A Rapoport
- Department of Cell Biology, Harvard Medical School, Boston, Massachusetts, United States of America
- * To whom correspondence should be addressed. E-mail:
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23
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Thakurta AG, Selvanathan SP, Patterson AD, Gopal G, Dhar R. The nuclear export signal of splicing factor Uap56p interacts with nuclear pore-associated protein Rae1p for mRNA export in Schizosaccharomyces pombe. J Biol Chem 2007; 282:17507-16. [PMID: 17449473 DOI: 10.1074/jbc.m609727200] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mammalian UAP56 or its homolog Sub2p in Saccharomyces cerevisiae are members of the ATP-dependent RNA helicase family and are required for splicing and nuclear export of mRNA. Previously we showed that in Schizosaccharomyces pombe Uap56p is critical for mRNA export. It links the mRNA adapter Mlo3p, a homolog of Yra1p in S. cerevisiae or Aly in mammals, to nuclear pore-associated mRNA export factor Rae1p. In this study we show that, in contrast to S. cerevisiae, Uap56p in S. pombe is not required for pre-mRNA splicing. The putative RNA helicase function of Uap56p is not required for mRNA export. However, the RNA-binding motif of Uap56p is critical for nuclear export of mRNA. Within Uap56p we identified nuclear import and export signals that may allow it to shuttle between the nucleus and the cytoplasm. We found that Uap56p interacts with Rae1p directly via its nuclear export signal, and this interaction is critical for the nuclear export activity of Uap56p as well as for exporting mRNA. RNA binding and the ability to shuttle between the nucleus and cytoplasm are important features of mRNA export carriers such as HIV-Rev. Our results suggest that Uap56p could function similarly as an export carrier of mRNA in S. pombe.
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Affiliation(s)
- Anjan G Thakurta
- Basic Research Laboratory, Center for Cancer Research, NCI, National Institutes of Health, Bethesda, Maryland 20892, USA
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24
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Mizuki F, Namiki T, Sato H, Furukawa H, Matsusaka T, Ohshima Y, Ishibashi R, Andoh T, Tani T. Participation of XPB/Ptr8p, a component of TFIIH, in nucleocytoplasmic transport of mRNA in fission yeast. Genes Cells 2007; 12:35-47. [PMID: 17212653 DOI: 10.1111/j.1365-2443.2006.01032.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
To identify novel factors involved in nuclear mRNA export in Schizosaccharomyces pombe, we isolated and characterized the ptr8(+) gene, mutation of which causes nuclear accumulation of poly (A)(+) RNA. The ptr8(+) gene encodes an S. pombe homologue of human XPB, a component of TFIIH involved in nucleotide excision repair (NER) and transcription. A temperature-sensitive mutant of ptr8(+) (ptr8-1) was highly sensitive to UV irradiation, as are human XPB cells. Northern blot analysis demonstrated that the amount of total poly (A)(+) mRNAs does not decrease significantly at the nonpermissive temperature in ptr8-1 cells, whereas a pulse-labeling assay using (35)S-methionine showed that protein synthesis decreases rapidly after incubation of cells at the nonpermissive temperature, suggesting that ptr8-1 cells have a defect in nuclear mRNA export. In Saccharomyces cerevisiae, a mutation in the SSL2 gene encoding a homologue of Ptr8p also causes a block of mRNA export at the nonpermissive temperature. In addition, expression of human XPB in ptr8-1 cells rescued the ts phenotype and the mRNA export defects, suggesting that human XPB may also play a role in mRNA export. Furthermore, we revealed a functional interaction between Ptr8p and Tho2p, a component of the TREX complex involved in mRNA export. These results suggest that XPB/Ptr8p plays roles not only in NER and transcription, but also plays a conserved role in mRNA export.
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Affiliation(s)
- Fumitaka Mizuki
- Department of Biological Sciences, Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555, Japan
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25
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Rollenhagen C, Hodge CA, Cole CN. Following temperature stress, export of heat shock mRNA occurs efficiently in cells with mutations in genes normally important for mRNA export. EUKARYOTIC CELL 2007; 6:505-13. [PMID: 17259545 PMCID: PMC1828927 DOI: 10.1128/ec.00317-06] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Heat shock leads to accumulation of polyadenylated RNA in nuclei of Saccharomyces cerevisiae cells, transcriptional induction of heat shock genes, and efficient export of polyadenylated heat shock mRNAs. These studies were conducted to examine the requirements for export of mRNA following heat shock. We used in situ hybridization to detect SSA4 mRNA (encoding Hsp70) and flow cytometry to measure the amount of Ssa4p-green fluorescent protein (GFP) produced following heat shock. Npl3p and Yra1p are mRNA-binding proteins recruited to nascent mRNAs and are essential for proper mRNA biogenesis and export. Heat shock mRNA was exported efficiently in temperature-sensitive npl3, yra1, and npl3 yra1 mutant strains. Nevertheless, Yra1p was recruited to heat shock mRNA, as were Nab2p and Npl3p. Interestingly, Yra1p was not recruited to heat shock mRNA in yra1-1 cells, suggesting that Npl3p is required for recruitment of Yra1p. The THO complex, which functions in transcription elongation and in recruitment of Yra1p, was not required for heat shock mRNA export, although normal mRNA export is impaired in growing cells lacking THO complex proteins. Taken together, these studies indicate that export following heat shock depends upon fewer factors than does mRNA export in growing cells. Furthermore, even though some mRNA-binding proteins are dispensable for efficient export of heat shock mRNA, those that are present in nuclei of heat shocked cells were recruited to heat shock mRNA.
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26
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Kendirgi F, Rexer DJ, Alcázar-Román AR, Onishko HM, Wente SR. Interaction between the shuttling mRNA export factor Gle1 and the nucleoporin hCG1: a conserved mechanism in the export of Hsp70 mRNA. Mol Biol Cell 2005; 16:4304-15. [PMID: 16000379 PMCID: PMC1196339 DOI: 10.1091/mbc.e04-11-0998] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Translocation of messenger RNAs through the nuclear pore complex (NPC) requires coordinated physical interactions between stable NPC components, shuttling transport factors, and mRNA-binding proteins. In budding yeast (y) and human (h) cells, Gle1 is an essential mRNA export factor. Nucleocytoplasmic shuttling of hGle1 is required for mRNA export; however, the mechanism by which hGle1 associates with the NPC is unknown. We have previously shown that the interaction of hGle1 with the nucleoporin hNup155 is necessary but not sufficient for targeting hGle1 to NPCs. Here, we report that the unique C-terminal 43 amino acid region of the hGle1B isoform mediates binding to the C-terminal non-FG region of the nucleoporin hCG1/NPL1. Moreover, hNup155, hGle1B, and hCG1 formed a heterotrimeric complex in vitro. This suggested that these two nucleoporins were required for the NPC localization of hGle1. Using an siRNA-based approach, decreased levels of hCG1 resulted in hGle1 accumulation in cytoplasmic foci. This was coincident with inhibition of heat shock-induced production of Hsp70 protein and export of the Hsp70 mRNA in HeLa cells. Because this closely parallels the role of the hCG1 orthologue yNup42/Rip1, we speculate that hGle1-hCG1 function in the mRNA export mechanism is highly conserved.
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Affiliation(s)
- Frederic Kendirgi
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232-8240, USA
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27
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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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28
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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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29
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Vanoosthuyse V, Valsdottir R, Javerzat JP, Hardwick KG. Kinetochore targeting of fission yeast Mad and Bub proteins is essential for spindle checkpoint function but not for all chromosome segregation roles of Bub1p. Mol Cell Biol 2004; 24:9786-801. [PMID: 15509783 PMCID: PMC525468 DOI: 10.1128/mcb.24.22.9786-9801.2004] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Several lines of evidence suggest that kinetochores are organizing centers for the spindle checkpoint response and the synthesis of a "wait anaphase" signal in cases of incomplete or improper kinetochore-microtubule attachment. Here we characterize Schizosaccharomyces pombe Bub3p and study the recruitment of spindle checkpoint components to kinetochores. We demonstrate by chromatin immunoprecipitation that they all interact with the central domain of centromeres, consistent with their role in monitoring kinetochore-microtubule interactions. Bub1p and Bub3p are dependent upon one another, but independent of the Mad proteins, for their kinetochore localization. We demonstrate a clear role for the highly conserved N-terminal domain of Bub1p in the robust targeting of Bub1p, Bub3p, and Mad3p to kinetochores and show that this is crucial for an efficient checkpoint response. Surprisingly, neither this domain nor kinetochore localization is required for other functions of Bub1p in chromosome segregation.
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Affiliation(s)
- Vincent Vanoosthuyse
- Wellcome Trust Centre for Cell Biology, ICMB, University of Edinburgh, Edinburgh EH9 3JR, United Kingdom
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Suntharalingam M, Alcázar-Román AR, Wente SR. Nuclear export of the yeast mRNA-binding protein Nab2 is linked to a direct interaction with Gfd1 and to Gle1 function. J Biol Chem 2004; 279:35384-91. [PMID: 15208322 DOI: 10.1074/jbc.m402044200] [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: 11/06/2022] Open
Abstract
Nuclear export of mRNA is mediated by interactions between soluble factors and nuclear pore complex (NPC) proteins. In Saccharomyces cerevisiae, Nab2 is an essential RNA-binding protein that shuttles between the nucleus and cytoplasm. The mechanism for trafficking of Nab2-bound mRNA through the NPC has not been defined. Gle1 is also required for mRNA export, and Gle1 interactions with NPC proteins, the RNA helicase Dbp5, and Gfd1 have been reported. Here we report that Nab2, Gfd1, and Gle1 associate in a complex. By using immobilized recombinant Gfd1, Nab2 was isolated from total yeast lysate. A similar biochemical assay with immobilized recombinant Nab2 resulted in coisolation of Gfd1 and Gle1. A Nab2-Gfd1 complex was also identified by coimmunoprecipitation from yeast lysates. In vitro binding assays with recombinant proteins revealed a direct association between Nab2 and Gfd1, and two-hybrid assays delineated Gfd1 binding to the N-terminal Nab2 domain. This N-terminal Nab2 domain is distinct from its RNA binding domains suggesting Nab2 could bind Gfd1 and RNA simultaneously. As Nab2 export was blocked in a gle1 mutant at the restrictive temperature, we propose a model wherein Gfd1 serves as a bridging factor between Gle1 and Nab2-bound mRNA during export.
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Affiliation(s)
- Mythili Suntharalingam
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee 37232, USA
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Andoh T, Azad AK, Shigematsu A, Ohshima Y, Tani T. The fission yeast ptr1+ gene involved in nuclear mRNA export encodes a putative ubiquitin ligase. Biochem Biophys Res Commun 2004; 317:1138-43. [PMID: 15094387 DOI: 10.1016/j.bbrc.2004.03.171] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2004] [Indexed: 10/26/2022]
Abstract
Fission yeast ptr1-1 is one of the mRNA transport mutants that accumulate poly(A)+ RNA in the nuclei at the nonpermissive temperature. We found that the ptr1+ gene encodes a homolog of Saccharomyces cerevisiae Tom1p, a hect type ubiquitin ligase. In ptr1-1, a conserved amino acid in the hect domain of Ptr1p is mutated. The ptr1+ gene is essential for growth and its mutation did not affect nuclear protein export. A ptr1-1 rae1-167 double mutant showed a synthetic effect on a growth defect, indicating that Ptr1p functionally interacts with an essential mRNA export factor Rae1p. We also isolated a multi-copy suppressor for ptr1-1 and found that it is the mpd2+ gene isolated as a multi-copy suppressor of cdc7-PD1.
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Affiliation(s)
- Tomoko Andoh
- Department of Biological Science, Faculty of Science, Kumamoto University, Kurokami, Kumamoto 860-8555, Japan
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Ideue T, Azad AK, Yoshida JI, Matsusaka T, Yanagida M, Ohshima Y, Tani T. The nucleolus is involved in mRNA export from the nucleus in fission yeast. J Cell Sci 2004; 117:2887-95. [PMID: 15161942 DOI: 10.1242/jcs.01155] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To elucidate the mechanism of mRNA export from the nucleus, we isolated five novel temperature-sensitive mutants (ptr7 to ptr11) that accumulate poly(A)(+) RNA in the nuclei at the nonpermissive temperature in Schizosaccharomyces pombe. Of those, the ptr11 mutation was found in the top2(+) gene encoding DNA topoisomerase II. In addition to the nuclear accumulation of poly(A)(+) RNA, ptr11 exhibited the cut (cell untimely torn) phenotype at the nonpermissive temperature, like the previously isolated mutant, ptr4. In these two mutants, cytokinesis occurred without prior nuclear division, resulting in cleavage of the undivided nuclei by the septum. To investigate the relationship between mRNA export defects and the cut phenotype observed in ptr4 and ptr11, we analyzed 11 other mutants displaying the cut phenotype and found that all these tested mutants accumulate poly(A)(+) mRNA in the aberrantly cleaved nuclei. Interestingly, nuclear accumulation of poly(A)(+) mRNA was observed only in the anucleolate nuclei produced by aberrant cytokinesis. In addition, nuc1, the S. pombe mutant exhibiting a collapsed nucleolus, trapped poly(A)(+) mRNA in the nucleolar region at the nonpermissive temperature. In ptr11 and nuc1, mRNA transcribed from the intron-containing TBP gene showed nuclear accumulation, but not transcripts from the intron-less TBP cDNA, suggesting that the export pathway differs between the spliced and unspliced TBP mRNAs. These findings support the notion that a subset of mRNAs in yeast is exported from the nucleus through transient association with the nucleolus.
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Affiliation(s)
- Takashi Ideue
- Department of Biology, Graduate School of Sciences, Kyushu University, Fukuoka 812-8581, Japan
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Thakurta AG, Gopal G, Yoon JH, Saha T, Dhar R. Conserved Nuclear Export Sequences in Schizosaccharomyces pombe Mex67 and Human TAP Function in mRNA Export by Direct Nuclear Pore Interactions. J Biol Chem 2004; 279:17434-42. [PMID: 14963046 DOI: 10.1074/jbc.m309731200] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Mex67, the homolog of human TAP, is not an essential mRNA export factor in Schizosaccharomyces pombe. Here we show that S. pombe encodes a homolog of the TAP cofactor that we have also named p15, whose function in mRNA export is not essential. We have identified and characterized two distinct nuclear export activities, nuclear export signal (NES) I and NES II, within the region of amino acids 434-509 of Mex67. These residues map within the known NTF2-like fold of TAP (amino acids 371-551). We show that the homologs of these two NESs are present and are functionally conserved in TAP. The NES I, NES II, and NES I + II of TAP and Mex67 directly bind with -phenylalanine-glycine (-FG)-containing sequences of S. pombe Nup159 and Nup98 but not with human p62. Mutants of NES I or NES II of Mex67/TAP that do not bind -FG Nup159 and Nup98 in vitro are unable to mediate nuclear export of a heterologous protein in S. pombe and in HeLa cells. Fused with the RNA recognition motifs (RRMs) of Crp79 and green fluorescent protein (GFP) (RRM-NES-GFP), the NES I and NES II of Mex67 or TAP can suppress the mRNA export defect of the Deltap15 rae1-167 synthetic lethal S. pombe strain, suggesting that the NESs can function in the absence of p15. These novel nuclear export sequences may provide additional routes for delivering Mex67/TAP to the nuclear pore complex.
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Affiliation(s)
- Anjan G Thakurta
- Center for Cancer Research, NCI and NICHD, National Institutes of Health, Bethesda, Maryland 20892, USA
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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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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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36
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Shamsher MK, Ploski J, Radu A. Karyopherin beta 2B participates in mRNA export from the nucleus. Proc Natl Acad Sci U S A 2002; 99:14195-9. [PMID: 12384575 PMCID: PMC137860 DOI: 10.1073/pnas.212518199] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Transport of macromolecules between the cell nucleus and cytoplasm occurs through the nuclear pores and is mediated by soluble carriers known as karyopherins (Kaps), transportins, importins, or exportins. We report that Kap beta2B (transportin-2) forms complexes with the mRNA export factor TAP in the presence of RanGTP, as shown by coimmunoprecipitation from HeLa cells. The interaction strictly depends on the presence of RanGTP. In digitonin-permeabilized cells, Kap beta2B mediates TAP-GFP export from the nuclei in the presence of RanGTP. A TAP mutant that does not coimmunoprecipitate with Kap beta2B is also not exported by Kap beta2B. In the permeabilized cells assay, TAP is also exported independently of Kap beta2B by direct interaction with nucleoporins, in agreement with previous reports. The export rate is, however, significantly lower than the Kap beta2B-mediated pathway. Both Kap beta2B and TAP are present and enriched in the poly(A)(+) RNA complexes isolated from HeLa cell nuclear lysates. Poly(A)(+) RNA strongly accumulates in the nuclei of HeLa cells treated with Kap beta2B short interfering RNA, indicating that Kap beta2B is involved in the export of at least a large proportion of the mRNA species. The export of beta-actin and GAPDH mRNA is also inhibited, whereas 28S RNA is not affected. The data support the conclusion that Kap beta2B participates directly in the export of a large proportion of cellular mRNAs, and TAP connects Kap beta2B to the mRNAs to be exported.
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Affiliation(s)
- Monee K Shamsher
- The Carl C. Icahn Institute for Gene Therapy and Molecular Medicine, Mount Sinai School of Medicine, Box 1496, 1425 Madison Avenue, New York, NY 10029, USA
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38
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Kozak L, Gopal G, Yoon JH, Sauna ZE, Ambudkar SV, Thakurta AG, Dhar R. Elf1p, a member of the ABC class of ATPases, functions as a mRNA export factor in Schizosacchromyces pombe. J Biol Chem 2002; 277:33580-9. [PMID: 12110682 DOI: 10.1074/jbc.m205415200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Rae1p and Mex67p/Tap are conserved mRNA export factors. We have used synthetic lethal genetic screens in Schizosaccharomyces pombe to identify mutations in genes that are functionally linked to rae1 and mex67 in mRNA export. From these screens, we have isolated mutations in a putative S. pombe homologue of the Candida albicans elf1 gene. The elf1 of S. pombe is not an essential gene. When elf1 mutations are combined with rae1-167 mutation, growth and mRNA export is inhibited in the double mutants. This inhibition can be suppressed by the multicopy expression of mex67 suggesting that Mex67p can substitute for the loss of Elf1p function. Elf1p is a non-membrane member of the ATP-binding cassette (ABC) class of ATPase and the GFP-Elf1p fusion localizes to the cytoplasm. Elf1p, expressed and purified from Escherichia coli, binds and hydrolyzes ATP. A mutant Elf1p that carries a glycine to aspartic acid (G731D) mutation within the Walker A domain of the second ATP site retains the ATP binding but loses its ATPase activity in vitro. This mutant protein no longer functions in mRNA export. Taken together, our results show that Elf1p functions as a mRNA export factor along with Rae1p and Mex67p in S. pombe.
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Affiliation(s)
- Libor Kozak
- Basic Research Laboratory, Center for Cancer Research, NCI/National Institutes of Health, Bldg. 37/Rm. 6138B, 9000 Rockville Pike, Bethesda, MD 20892, USA
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39
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Braun IC, Herold A, Rode M, Izaurralde E. Nuclear export of mRNA by TAP/NXF1 requires two nucleoporin-binding sites but not p15. Mol Cell Biol 2002; 22:5405-18. [PMID: 12101235 PMCID: PMC133933 DOI: 10.1128/mcb.22.15.5405-5418.2002] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Metazoan NXF1/p15 heterodimers promote export of bulk mRNA through nuclear pore complexes (NPC). NXF1 interacts with the NPC via two distinct structural domains, the UBA-like domain and the NTF2-like scaffold, which results from the heterodimerization of the NTF2-like domain of NXF1 with p15. Both domains feature a single nucleoporin-binding site, and they act synergistically to promote NPC translocation. Whether the NTF2-like scaffold (and thereby p15) contributes only to NXF1/NPC association or is also required for other functions, e.g., to impart directionality to the export process by regulating NXF1/NPC or NXF1/cargo interactions, remains unresolved. Here we show that a minimum of two nucleoporin-binding sites is required for NXF1-mediated export of cellular mRNA. These binding sites can be provided by an NTF2-like scaffold followed by a UBA-like domain (as in the wild-type protein) or by two NTF2-like scaffolds or two UBA-like domains in tandem. In the latter case, the export activity of NXF1 is independent of p15. Thus, as for the UBA-like domain, the function of the NTF2-like scaffold is confined to nucleoporin binding. More importantly, two copies of either of these domains are sufficient to promote directional transport of mRNA cargoes across the NPC.
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Affiliation(s)
- Isabelle C Braun
- European Molecular Biology Laboratory, Meyerhofstrasse 1, D-69117 Heidelberg, Germany
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40
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Thakurta AG, Whalen WA, Yoon JH, Bharathi A, Kozak L, Whiteford C, Love DC, Hanover JA, Dhar R. Crp79p, like Mex67p, is an auxiliary mRNA export factor in Schizosaccharomyces pombe. Mol Biol Cell 2002; 13:2571-84. [PMID: 12181330 PMCID: PMC117926 DOI: 10.1091/mbc.e01-11-0133] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The export of mRNA from the nucleus to the cytoplasm involves interactions of proteins with mRNA and the nuclear pore complex. We isolated Crp79p, a novel mRNA export factor from the same synthetic lethal screen that led to the identification of spMex67p in Schizosaccharomyces pombe. Crp79p is a 710-amino-acid-long protein that contains three RNA recognition motif domains in tandem and a distinct C-terminus. Fused to green fluorescent protein (GFP), Crp79p localizes to the cytoplasm. Like Mex67p, Crp79-GFP binds poly(A)(+) RNA in vivo, shuttles between the nucleus and the cytoplasm, and contains a nuclear export activity at the C-terminus that is Crm1p-independent. All of these properties are essential for Crp79p to promote mRNA export. Crp79p import into the nucleus depends on the Ran system. A domain of spMex67p previously identified as having a nuclear export activity can functionally substitute for the nuclear export activity at the C-terminus of Crp79p. Although both Crp79p and spMex67p function to export mRNA, Crp79p does not substitute for all of spMex67p functions and probably is not a functional homologue of spMex67p. We propose that Crp79p is a nonessential mRNA export carrier in S. pombe.
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Affiliation(s)
- Anjan G Thakurta
- Basic Research Laboratory, National Cancer Institute, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA
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Thakurta AG, Ho Yoon J, Dhar R. Schizosaccharomyces pombe spPABP, a homologue of Saccharomyces cerevisiae Pab1p, is a non-essential, shuttling protein that facilitates mRNA export. Yeast 2002; 19:803-10. [PMID: 12112233 DOI: 10.1002/yea.876] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Poly(A)-binding proteins play important roles in mRNA metabolism in eukaryotic cells. We examined the role of the Schizosaccharomyces pombe homologue of the Saccharomyces cerevisiae poly(A)-binding protein, Pab1p, in cellular growth and mRNA export. In contrast to PAB1, the sppabp gene is not essential for cellular viability. Like the human hPABP1 protein, spPABP is cytoplasmically localized and can shuttle between the nucleus and the cytoplasm. We found that a spPABP-GFP fusion protein expressed from a multicopy plasmid could suppress the growth and mRNA export defect of rae1-16 7 nup184-1 synthetic lethal mutations. However, about 20-25% of cells in the population exhibited a pronounced nuclear accumulation of poly(A)(+) RNA. The same cells also localized the spPABP-GFP fusion to the nucleus, suggesting that the shuttling ability of spPABP is related to its function in mRNA export. When a heterologous nuclear export activity from spMex67p was fused to spPABP-GFP fusion protein, it overcame the nuclear retention but did not increase nuclear mRNA export. We discuss the implications of these observations in relation to how spPABP could function in mRNA export. Published in 2002 by John Wiley & Sons, Ltd.
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Affiliation(s)
- Anjan G Thakurta
- Basic Research Laboratory, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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Dreyfuss G, Kim VN, Kataoka N. Messenger-RNA-binding proteins and the messages they carry. Nat Rev Mol Cell Biol 2002; 3:195-205. [PMID: 11994740 DOI: 10.1038/nrm760] [Citation(s) in RCA: 1092] [Impact Index Per Article: 49.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
From sites of transcription in the nucleus to the outreaches of the cytoplasm, messenger RNAs are associated with RNA-binding proteins. These proteins influence pre-mRNA processing as well as the transport, localization, translation and stability of mRNAs. Recent discoveries have shown that one group of these proteins marks exon exon junctions and has a role in mRNA export. These proteins communicate crucial information to the translation machinery for the surveillance of nonsense mutations and for mRNA localization and translation.
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Affiliation(s)
- Gideon Dreyfuss
- Howard Hughes Medical Institute and Department of Biochemistry and Biophysics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104-6148, USA.
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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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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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Wilkie GS, Zimyanin V, Kirby R, Korey C, Francis-Lang H, Van Vactor D, Davis I. Small bristles, the Drosophila ortholog of NXF-1, is essential for mRNA export throughout development. RNA (NEW YORK, N.Y.) 2001; 7:1781-1792. [PMID: 11780634 PMCID: PMC1370217] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We identified a temperature-sensitive allele of small bristles (sbr), the Drosophila ortholog of human TAP/NXF-1 and yeast Mex67, in a screen for mutants defective in mRNA export. We show that sbr is essential for the nuclear export of all mRNAs tested in a wide range of tissues and times in development. High resolution and sensitive in situ hybridization detect the rapid accumulation of individual mRNA species in sbr mutant nuclei in particles that are distinct from nascent transcript foci and resemble wild-type export intermediates. The particles become more numerous and intense with increasing time at the restrictive temperature and are exported very rapidly after shifting back to the permissive temperature. The mRNA export block is not due indirectly to a defect in splicing, nuclear protein import, or aberrant nuclear ultrastructure, suggesting that in sbr mutants, mRNA is competent for export but fails to dock or translocate through NPCs. We conclude that NXF-1 is an essential ubiquitous export factor for all mRNAs throughout development in higher eukaryotes.
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Affiliation(s)
- G S Wilkie
- Wellcome Trust Centre for Cell Biology, Institute of Cell and Molecular Biology, University of Edinburgh, Scotland, United Kingdom
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46
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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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Abstract
The addition of O-linked N-acetylglucosamine (O-GlcNAc) to target proteins may serve as a signaling modification analogous to protein phosphorylation. Like phosphorylation, O-GlcNAc is a dynamic modification occurring in the nucleus and cytoplasm. Various analytical methods have been developed to detect O-GlcNAc and distinguish it from glycosylation in the endomembrane system. Many target molecules have been identified; these targets are typically components of supramolecular complexes such as transcription factors, nuclear pore proteins, or cytoskeletal components. The enzymes responsible for O-GlcNAc addition and removal are highly conserved molecules having molecular features consistent with a signaling role. The O-GlcNAc transferase and O-GlcNAcase are likely to act in consort with kinases and phosphatases generating various isoforms of physiological substrates. These isoforms may differ in such properties as protein-protein interactions, protein stability, and enzymatic activity. Since O-GlcNAc plays a critical role in the regulation of signaling pathways of higher plants, the glycan modification is likely to perform similar signaling functions in mammalian cells. Glucose and amino acid metabolism generates hexosamine precursors that may be key regulators of a nutrient sensing pathway involving O-GlcNAc signaling. Altered O-linked GlcNAc metabolism may also occur in human diseases including neurodegenerative disorders, diabetes mellitus and cancer.
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Affiliation(s)
- J A Hanover
- LCBB, NIDDK, National Institutes of Health, Bethesda, MD 20892, USA.
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Current awareness on yeast. Yeast 2001; 18:1091-8. [PMID: 11481679 DOI: 10.1002/yea.688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
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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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Abstract
Export of mRNA through nuclear pore complexes (NPC) is preceded by multiple and well coordinated processing steps, resulting in the formation of an export competent ribonucleoprotein complex (mRNP). Numerous factors involved in the translocation of the mRNP through the NPC and its release into the cytoplasm have been isolated mainly through genetic approaches in yeast, and putative functional homologues have been identified in metazoan systems. Understanding the mechanism of mRNA export relies, in part, on the functional characterization of these factors and the establishment of a complete network of molecular interactions. Here we summarize recent progress in the characterization of yeast and mammalian components implicated in the export of an mRNA from the nucleus to the cytoplasm.
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Affiliation(s)
- D Zenklusen
- Institute of Microbiology, Centre Hospitalier Universitaire Vaudois, 44, rue du Bugnon, 1011, Lausanne, Switzerland
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