1
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Kim JW, Yong AJH, Aisenberg EE, Lobel JH, Wang W, Dawson TM, Dawson VL, Gao R, Jan YN, Bateup HS, Ingolia NT. Molecular recording of calcium signals via calcium-dependent proximity labeling. Nat Chem Biol 2024; 20:894-905. [PMID: 38658655 DOI: 10.1038/s41589-024-01603-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2023] [Accepted: 03/08/2024] [Indexed: 04/26/2024]
Abstract
Calcium ions serve as key intracellular signals. Local, transient increases in calcium concentrations can activate calcium sensor proteins that in turn trigger downstream effectors. In neurons, calcium transients play a central role in regulating neurotransmitter release and synaptic plasticity. However, it is challenging to capture the molecular events associated with these localized and ephemeral calcium signals. Here we present an engineered biotin ligase that generates permanent molecular traces in a calcium-dependent manner. The enzyme, calcium-dependent BioID (Cal-ID), biotinylates nearby proteins within minutes in response to elevated local calcium levels. The biotinylated proteins can be identified via mass spectrometry and visualized using microscopy. In neurons, Cal-ID labeling is triggered by neuronal activity, leading to prominent protein biotinylation that enables transcription-independent activity labeling in the brain. In summary, Cal-ID produces a biochemical record of calcium signals and neuronal activity with high spatial resolution and molecular specificity.
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Affiliation(s)
- J Wren Kim
- Department of Molecular and Cell Biology at the University of California, Berkeley, Berkeley, CA, USA
| | - Adeline J H Yong
- Department of Physiology at the University of California, San Francisco, San Francisco, CA, USA
- Howard Hughes Medical Institute at the University of California, San Francisco, San Francisco, CA, USA
| | - Erin E Aisenberg
- Helen Wills Neuroscience Institute at the University of California, Berkeley, Berkeley, CA, USA
| | - Joseph H Lobel
- Department of Molecular and Cell Biology at the University of California, Berkeley, Berkeley, CA, USA
| | - Wei Wang
- Department of Chemistry at the University of Illinois, Chicago, Chicago, IL, USA
| | - Ted M Dawson
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Valina L Dawson
- Institute for Cell Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Ruixuan Gao
- Department of Chemistry at the University of Illinois, Chicago, Chicago, IL, USA
| | - Yuh Nung Jan
- Department of Physiology at the University of California, San Francisco, San Francisco, CA, USA
- Howard Hughes Medical Institute at the University of California, San Francisco, San Francisco, CA, USA
| | - Helen S Bateup
- Department of Molecular and Cell Biology at the University of California, Berkeley, Berkeley, CA, USA
- Helen Wills Neuroscience Institute at the University of California, Berkeley, Berkeley, CA, USA
- Chan Zuckerberg Biohub, San Francisco, CA, USA
| | - Nicholas T Ingolia
- Department of Molecular and Cell Biology at the University of California, Berkeley, Berkeley, CA, USA.
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2
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Moraleva A, Deryabin A, Kordyukova M, Polzikov M, Shishova K, Dobrochaeva K, Rubtsov Y, Rubtsova M, Dontsova O, Zatsepina O. Human nucleolar protein SURF6/RRP14 participates in early steps of pre-rRNA processing. PLoS One 2023; 18:e0285833. [PMID: 37450438 PMCID: PMC10348582 DOI: 10.1371/journal.pone.0285833] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Accepted: 05/02/2023] [Indexed: 07/18/2023] Open
Abstract
The biogenesis of ribosomes requires tightly controlled transcription and processing of pre-rRNA which comprises ribosomal RNAs forming the core of large and small ribosomal subunits. Early steps of the pre-rRNA processing and assembly of the ribosomal subunits require a large set of proteins that perform folding and nucleolytic cleavage of pre-rRNAs in the nucleoli. Structure and functions of proteins involved in the pre-rRNA processing have been extensively studied in the budding yeast S. cerevisiae. Functional characterization of their human homologues is complicated by the complexity of mammalian ribosomes and increased number of protein factors involved in the ribosomal biogenesis. Homologues of human nucleolar protein SURF6 from yeast and mouse, Rrp14 and Surf6, respectively, had been shown to be involved in the early steps of pre-rRNA processing. Rrp14 works as RNA chaperone in complex with proteins Ssf1 and Rrp15. Human SURF6 knockdown and overexpression were used to clarify a role of SURF6 in the early steps of pre-rRNA processing in human cell lines HeLa and HTC116. By analyzing the abundance of the rRNA precursors in cells with decreased level or overexpression of SURF6, we demonstrated that human SURF6 is involved in the maturation of rRNAs from both small and large ribosomal subunits. Changes in the SURF6 level caused by knockdown or overexpression of the protein do not result in the death of HeLa cells in contrast to murine embryonic fibroblasts, but significantly alter the distribution of cells among the phases of the cell cycle. SURF6 knockdown in both p53 sufficient and p53 deficient HCT116 human cancer cells results in elongation of G0/G1 and shortening of G2/M phase. This surprising result suggests p53 independence of SURF6 effects on the cell cycle and possible multiple functions of SURF6. Our data point to the shift from pathway 1 to pathway 2 of the rRNA biogenesis caused by the SURF6 knockdown and its likely association with p53 pathway.
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Affiliation(s)
- Anastasiia Moraleva
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS, Moscow, Russian Federation
| | - Alexander Deryabin
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS, Moscow, Russian Federation
| | - Maria Kordyukova
- Federal Center of Brain Research and Neurotechnologies of the Federal Medical Biological Agency, Moscow, Russian Federation
| | - Mikhail Polzikov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS, Moscow, Russian Federation
| | - Kseniya Shishova
- Federal Center of Brain Research and Neurotechnologies of the Federal Medical Biological Agency, Moscow, Russian Federation
| | - Kira Dobrochaeva
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS, Moscow, Russian Federation
| | - Yury Rubtsov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS, Moscow, Russian Federation
| | - Maria Rubtsova
- Department of Chemistry, Lomonosov Moscow State University, Moscow, Russian Federation
| | - Olga Dontsova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS, Moscow, Russian Federation
- Department of Chemistry, Lomonosov Moscow State University, Moscow, Russian Federation
- SkolTech, Moscow, Russian Federation
| | - Olga Zatsepina
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry RAS, Moscow, Russian Federation
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3
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Dörner K, Ruggeri C, Zemp I, Kutay U. Ribosome biogenesis factors-from names to functions. EMBO J 2023; 42:e112699. [PMID: 36762427 PMCID: PMC10068337 DOI: 10.15252/embj.2022112699] [Citation(s) in RCA: 26] [Impact Index Per Article: 26.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2022] [Revised: 12/13/2022] [Accepted: 01/19/2023] [Indexed: 02/11/2023] Open
Abstract
The assembly of ribosomal subunits is a highly orchestrated process that involves a huge cohort of accessory factors. Most eukaryotic ribosome biogenesis factors were first identified by genetic screens and proteomic approaches of pre-ribosomal particles in Saccharomyces cerevisiae. Later, research on human ribosome synthesis not only demonstrated that the requirement for many of these factors is conserved in evolution, but also revealed the involvement of additional players, reflecting a more complex assembly pathway in mammalian cells. Yet, it remained a challenge for the field to assign a function to many of the identified factors and to reveal their molecular mode of action. Over the past decade, structural, biochemical, and cellular studies have largely filled this gap in knowledge and led to a detailed understanding of the molecular role that many of the players have during the stepwise process of ribosome maturation. Such detailed knowledge of the function of ribosome biogenesis factors will be key to further understand and better treat diseases linked to disturbed ribosome assembly, including ribosomopathies, as well as different types of cancer.
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Affiliation(s)
- Kerstin Dörner
- Department of Biology, Institute of Biochemistry, ETH Zurich, Zurich, Switzerland.,Molecular Life Sciences Ph.D. Program, Zurich, Switzerland
| | - Chiara Ruggeri
- Department of Biology, Institute of Biochemistry, ETH Zurich, Zurich, Switzerland.,RNA Biology Ph.D. Program, Zurich, Switzerland
| | - Ivo Zemp
- Department of Biology, Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
| | - Ulrike Kutay
- Department of Biology, Institute of Biochemistry, ETH Zurich, Zurich, Switzerland
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4
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Lin Z, Liu H, Chen H, Cao H, Liu X, Zhu H, Zhao L, Chen Z. Rrp14 controls rRNA transcription via facilitating the translocation of Pol5 into the nucleolus. Cell Cycle 2022; 21:489-500. [PMID: 34974803 PMCID: PMC8942550 DOI: 10.1080/15384101.2021.2023303] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Rrp14 is a conserved protein that plays an important role in rRNA processing and ribosomal biogenesis. In Schizosaccharomyces pombe, the rrp14 gene is split into SPAC8C9.10 c (rrp14) and SPBC947.07 (rrp1402). Although the SPAC8C9.10 c gene is not essential for S. pombe survival, deletion of the gene causes the yeast cells to grow sick and to exhibit decreased rRNA transcription. We identified a novel Pol5 protein that physically interacts with the Rrp14 protein. Taking advantage of the Pil1 co-tethering assay, we found that Rrp14 facilitates the nucleolus translocation of Pol5, and the 7-RINAWN-12 motif of the Rrp14 protein is responsible for the interaction between Pol5 and Rrp14. Since deletion of the 7-RINAWN-12 motif affects rRNA transcription, we thus propose that Rrp14 affects rRNA transcription by facilitating the nucleolus translocation of Pol5.
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Affiliation(s)
- Zhen Lin
- Department of Forensic Medicine, Basic Medical College, Jilin University, Jilin, China
| | - Haiyan Liu
- Department of Forensic Medicine, Basic Medical College, Jilin University, Jilin, China
| | - Hongzhi Chen
- Department of Forensic Medicine, Basic Medical College, Jilin University, Jilin, China
| | - Hongshi Cao
- Nursing Department, The First Hospital, Jilin University, Jilin, China
| | - Xiaochang Liu
- Department of Forensic Medicine, Basic Medical College, Jilin University, Jilin, China
| | - Haichao Zhu
- Department of Forensic Medicine, Basic Medical College, Jilin University, Jilin, China
| | - Lu Zhao
- Department of Forensic Medicine, Basic Medical College, Jilin University, Jilin, China
| | - Zhiming Chen
- Department of Forensic Medicine, Basic Medical College, Jilin University, Jilin, China,CONTACT Zhiming Chen Department of Forensic Medicine, Basic Medical College, Jilin University, No. 125, Xinjiang street, Changchun City, Jilin Province, Jilin, 130021. China
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5
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Wei C, Wang B, Chen ZH, Xiao H, Tang L, Guan JF, Yuan RF, Yu X, Hu ZG, Wu HJ, Dai Z, Wang K. Validating RRP12 Expression and Its Prognostic Significance in HCC Based on Data Mining and Bioinformatics Methods. Front Oncol 2022; 12:812009. [PMID: 35178347 PMCID: PMC8844371 DOI: 10.3389/fonc.2022.812009] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 01/11/2022] [Indexed: 12/26/2022] Open
Abstract
RRP12 (ribosomal RNA processing 12 homolog) is a nucleolar protein involved in the maturation and transport of eukaryotic ribosomal subunits and is a type of RNA binding protein. In recent years, considerable research has indicated that RRP12 is associated with the occurrence and development of multiple cancers. However, there is no research on RRP12 in hepatocellular carcinoma. Herein, we aimed to explore the role and significance of RRP12 in hepatocellular carcinoma.We used the TIMER and GEPIA databases to perform pan-cancer analyses of RRP12. The impact of RRP12 on the prognosis was analyzed through the GEPIA database. The relationship between RRP12 and immune cell infiltration was investigated by TIMER and GEPIA databases. Moreover, the expression of RRP12 in various liver cancer cells was evaluated by Western Blot to determine the cell line for the next experiment. Scratch test, Transwell test, and Edu tests were applied to validate the effects of RRP12 on the function of liver cancer cells. And the data were statistically analyzed.Pan-cancer analysis found that RPP12 was significantly upregulated in many cancers. Moreover, the prognostic analysis revealed that the difference in the expression of RRP12 has statistical significance for the overall survival rate and disease-free survival rate of liver cancer patients. In order to analyze the correlation between the expression level of RRP12 and clinical parameters, it was found that there was a significant negative correlation with tumor stage, tumor grade and tumor size. Univariate and multivariate analysis showed that RRP12 could be used as an independent prognostic factor for patients with hepatocellular carcinoma. Cellular experiments have proved that knocking down RRP12 can inhibit the proliferation, invasion, and metastasis of liver cancer cells.Therefore, RRP12 significantly affects the occurrence and development of HCC. Hence, RRP12 can become a potential target and prognostic biomarker for the treatment of hepatocellular carcinoma.
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Affiliation(s)
- Chao Wei
- Hepato-Biliary-Pancreatic Surgery Division, Department of General Surgery, The Second Affiliated Hospital of Nanchang University, Nanchang, China.,Second Affiliated Hospital of Nanchang University, Jiangxi Province Key Laboratory of Molecular Medicine, Nanchang, China.,Second Affiliated Hospital of Nanchang University, Jiangxi Province Engineering Research Center of Hepatobiliary Disease, Nanchang, China
| | - Ben Wang
- Hepato-Biliary-Pancreatic Surgery Division, Department of General Surgery, The Second Affiliated Hospital of Nanchang University, Nanchang, China.,Second Affiliated Hospital of Nanchang University, Jiangxi Province Key Laboratory of Molecular Medicine, Nanchang, China.,Second Affiliated Hospital of Nanchang University, Jiangxi Province Engineering Research Center of Hepatobiliary Disease, Nanchang, China
| | - Zhong-Huo Chen
- Hepato-Biliary-Pancreatic Surgery Division, Department of General Surgery, The Second Affiliated Hospital of Nanchang University, Nanchang, China.,Second Affiliated Hospital of Nanchang University, Jiangxi Province Key Laboratory of Molecular Medicine, Nanchang, China.,Second Affiliated Hospital of Nanchang University, Jiangxi Province Engineering Research Center of Hepatobiliary Disease, Nanchang, China
| | - Han Xiao
- Department of Hepato-Biliary-Pancreatic Surgery, Jiujiang First People's Hospital, Jiujiang, China
| | - Lei Tang
- Hepato-Biliary-Pancreatic Surgery Division, Department of General Surgery, The Second Affiliated Hospital of Nanchang University, Nanchang, China.,Second Affiliated Hospital of Nanchang University, Jiangxi Province Key Laboratory of Molecular Medicine, Nanchang, China.,Second Affiliated Hospital of Nanchang University, Jiangxi Province Engineering Research Center of Hepatobiliary Disease, Nanchang, China
| | - Jia-Fu Guan
- Hepato-Biliary-Pancreatic Surgery Division, Department of General Surgery, The Second Affiliated Hospital of Nanchang University, Nanchang, China.,Second Affiliated Hospital of Nanchang University, Jiangxi Province Engineering Research Center of Hepatobiliary Disease, Nanchang, China
| | - Rong-Fa Yuan
- Hepato-Biliary-Pancreatic Surgery Division, Department of General Surgery, The Second Affiliated Hospital of Nanchang University, Nanchang, China.,Second Affiliated Hospital of Nanchang University, Jiangxi Province Engineering Research Center of Hepatobiliary Disease, Nanchang, China.,Second Affiliated Hospital of Nanchang University, Jiangxi Provincial Clinical Research Center for General Surgery Disease, Nanchang, China
| | - Xin Yu
- Hepato-Biliary-Pancreatic Surgery Division, Department of General Surgery, The Second Affiliated Hospital of Nanchang University, Nanchang, China.,Second Affiliated Hospital of Nanchang University, Jiangxi Province Engineering Research Center of Hepatobiliary Disease, Nanchang, China.,Second Affiliated Hospital of Nanchang University, Jiangxi Provincial Clinical Research Center for General Surgery Disease, Nanchang, China
| | - Zhi-Gang Hu
- Hepato-Biliary-Pancreatic Surgery Division, Department of General Surgery, The Second Affiliated Hospital of Nanchang University, Nanchang, China.,Second Affiliated Hospital of Nanchang University, Jiangxi Province Engineering Research Center of Hepatobiliary Disease, Nanchang, China.,Second Affiliated Hospital of Nanchang University, Jiangxi Provincial Clinical Research Center for General Surgery Disease, Nanchang, China
| | - Hua-Jun Wu
- Hepato-Biliary-Pancreatic Surgery Division, Department of General Surgery, The Second Affiliated Hospital of Nanchang University, Nanchang, China.,Second Affiliated Hospital of Nanchang University, Jiangxi Province Engineering Research Center of Hepatobiliary Disease, Nanchang, China.,Second Affiliated Hospital of Nanchang University, Jiangxi Provincial Clinical Research Center for General Surgery Disease, Nanchang, China
| | - Zhi Dai
- Liver Cancer Institute, Zhongshan Hospital, Fudan University, Shanghai, China
| | - Kai Wang
- Hepato-Biliary-Pancreatic Surgery Division, Department of General Surgery, The Second Affiliated Hospital of Nanchang University, Nanchang, China.,Second Affiliated Hospital of Nanchang University, Jiangxi Province Engineering Research Center of Hepatobiliary Disease, Nanchang, China.,Second Affiliated Hospital of Nanchang University, Jiangxi Provincial Clinical Research Center for General Surgery Disease, Nanchang, China
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6
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Moraleva AA, Malysheva MA, Khajdukov SV, Zatsepina OV. A Higher Level of Expression of the Nucleolar Protein SURF6 in Human Normal Activated Lymphocytes and in Lymphocytes of Patients with Lymphoproliferative Disorders. DOKL BIOCHEM BIOPHYS 2020; 494:261-265. [PMID: 33119830 DOI: 10.1134/s1607672920050099] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2020] [Revised: 06/29/2020] [Accepted: 06/29/2020] [Indexed: 11/22/2022]
Abstract
Proliferation of mammalian cells is often accompanied by an increase in the content of the nucleolar proteins, which allows researchers to consider such proteins as potential activation markers. To test this assumption experimentally, we examined the expression pattern of the nucleolar rRNA processing factor SURF6 in normal (resting) peripheral blood lymphocytes, lymphocytes activated for proliferation in vitro, and in blood samples from patients with lymphoproliferative diseases. Using two methods (immunofluorescence and immunoblotting), we for the first time showed that the SURF6 protein is not detected in normal lymphocytes but can easily be visualized in lymphocytes after PHA activation and in lymphocytes of lymphocytic leukemia patients. The level of SURF6 expression in patients correlated with the aggressiveness of the disease development determined by the content of Ki-67-positive lymphocytes. These results allow the SURF6 nucleolar protein to be considered as a putative activation marker of lymphocytes in human blood disorders.
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Affiliation(s)
- A A Moraleva
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Science, Moscow, Russia
| | - M A Malysheva
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Science, Moscow, Russia
| | - S V Khajdukov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Science, Moscow, Russia
| | - O V Zatsepina
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Science, Moscow, Russia.
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7
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Ferrolino MC, Mitrea DM, Michael JR, Kriwacki RW. Compositional adaptability in NPM1-SURF6 scaffolding networks enabled by dynamic switching of phase separation mechanisms. Nat Commun 2018; 9:5064. [PMID: 30498217 PMCID: PMC6265330 DOI: 10.1038/s41467-018-07530-1] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2018] [Accepted: 11/08/2018] [Indexed: 12/18/2022] Open
Abstract
The nucleolus, the site for ribosome biogenesis contains hundreds of proteins and several types of RNA. The functions of many non-ribosomal nucleolar proteins are poorly understood, including Surfeit locus protein 6 (SURF6), an essential disordered protein with roles in ribosome biogenesis and cell proliferation. SURF6 co-localizes with Nucleophosmin (NPM1), a highly abundant protein that mediates the liquid-like features of the granular component region of the nucleolus through phase separation. Here, we show that electrostatically-driven interactions between disordered regions of NPM1 and SURF6 drive liquid-liquid phase separation. We demonstrate that co-existing heterotypic (NPM1-SURF6) and homotypic (NPM1-NPM1) scaffolding interactions within NPM1-SURF6 liquid-phase droplets dynamically and seamlessly interconvert in response to variations in molecular crowding and protein concentrations. We propose a mechanism wherein NPM1-dependent nucleolar scaffolds are modulated by non-ribosomal proteins through active rearrangements of interaction networks that can possibly contribute to the directionality of ribosomal biogenesis within the liquid-like nucleolus. The nucleolus is a membrane-less organelle and both Nucleophosmin (NPM1) and Surfeit locus protein 6 (SURF6) are abundant proteins within the nucleolus. Here the authors employ biophysical methods to study the properties of NPM1-S6N droplets and provide insights into the role of SURF6 in maintaining and modulating the liquid-like structure of the nucleolus.
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Affiliation(s)
- Mylene C Ferrolino
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Diana M Mitrea
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - J Robert Michael
- Department of Computational Biology, St. Jude Children's Research Hospital, Memphis, TN, USA
| | - Richard W Kriwacki
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, TN, USA. .,Department of Microbiology, Immunology and Biochemistry, University of Tennessee Health Sciences Center, Memphis, TN, USA.
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8
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Moraleva A, Magoulas C, Polzikov M, Hacot S, Mertani HC, Diaz JJ, Zatsepina O. Involvement of the specific nucleolar protein SURF6 in regulation of proliferation and ribosome biogenesis in mouse NIH/3T3 fibroblasts. Cell Cycle 2017; 16:1979-1991. [PMID: 28873013 DOI: 10.1080/15384101.2017.1371880] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The nucleolar proteins which link cell proliferation to ribosome biogenesis are regarded to be potentially oncogenic. Here, in order to examine the involvement of an evolutionary conserved nucleolar protein SURF6/Rrp14 in proliferation and ribosome biogenesis in mammalian cells, we established stably transfected mouse NIH/3T3 fibroblasts capable of conditional overexpression of the protein. Cell proliferation was monitored in real-time, and various cell cycle parameters were quantified based on flow cytometry, Br-dU-labeling and conventional microscopy data. We show that overexpression of SURF6 accelerates cell proliferation and promotes transition through all cell cycle phases. The most prominent SURF6 pro-proliferative effects include a significant reduction of the population doubling time, from 19.8 ± 0.7 to 16.2 ± 0.5 hours (t-test, p < 0.001), and of the length of cell division cycle, from 17.6 ± 0.6 to 14.0 ± 0.4 hours (t-test, p < 0.001). The later was due to the shortening of all cell cycle phases but the length of G1 period was reduced most, from 5.7 ± 0.4 to 3.8 ± 0.3 hours, or by ∼30%, (t-test, p < 0.05). By Northern blots and qRT-PCR, we further showed that the acceleration of cell proliferation was concomitant with an accumulation of rRNA species along both ribosomal subunit maturation pathways. It is evident, therefore, that like the yeast homologue Rrp14, mammalian SURF6 is involved in various steps of rRNA processing during ribosome biogenesis. We concluded that SURF6 is a novel positive regulator of proliferation and G1/S transition in mammals, implicating that SURF6 is a potential oncogenic protein, which can be further studied as a putative target in anti-cancer therapy.
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Affiliation(s)
- Anastasiia Moraleva
- a Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences , Moscow , Russian Federation
| | - Charalambos Magoulas
- b Centre for Investigative and Diagnostic Oncology, Department of Natural Sciences, School of Science and Technology , Middlesex University , London , United Kingdom
| | - Mikhail Polzikov
- a Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences , Moscow , Russian Federation
| | - Sabine Hacot
- c Centre de Recherche en Cancérologie de Lyon, UMR INSERM 1052-CNRS 5286, Centre Léon Bérard , Université Claude Bernard Lyon I, Université de Lyon , Lyon , France
| | - Hichem C Mertani
- c Centre de Recherche en Cancérologie de Lyon, UMR INSERM 1052-CNRS 5286, Centre Léon Bérard , Université Claude Bernard Lyon I, Université de Lyon , Lyon , France
| | - Jean-Jacques Diaz
- c Centre de Recherche en Cancérologie de Lyon, UMR INSERM 1052-CNRS 5286, Centre Léon Bérard , Université Claude Bernard Lyon I, Université de Lyon , Lyon , France
| | - Olga Zatsepina
- a Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences , Moscow , Russian Federation.,c Centre de Recherche en Cancérologie de Lyon, UMR INSERM 1052-CNRS 5286, Centre Léon Bérard , Université Claude Bernard Lyon I, Université de Lyon , Lyon , France
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9
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Wang YL, Chen H, Zhan YQ, Yin RH, Li CY, Ge CH, Yu M, Yang XM. EWSR1 regulates mitosis by dynamically influencing microtubule acetylation. Cell Cycle 2016; 15:2202-2215. [PMID: 27341063 DOI: 10.1080/15384101.2016.1200774] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022] Open
Abstract
EWSR1, participating in transcription and splicing, has been identified as a translocation partner for various transcription factors, resulting in translocation, which in turn plays crucial roles in tumorigenesis. Recent studies have investigated the role of EWSR1 in mitosis. However, the effect of EWSR1 on mitosis is poorly understood. Here, we observed that depletion of EWSR1 resulted in cell cycle arrest in the mitotic phase, mainly due to an increase in the time from nuclear envelope breakdown to metaphase, resulting in a high percentage of unaligned chromosomes and multipolar spindles. We also demonstrated that EWSR1 is a spindle-associated protein that interacts with α-tubulin during mitosis. EWSR1 depletion increased the cold-sensitivity of spindle microtubules, and decreased the rate of spindle assembly. EWSR1 regulated the level of microtubule acetylation in the mitotic spindle; microtubule acetylation was rescued in EWSR1-depleted mitotic cells following suppression of HDAC6 activity by its specific inhibitor or siRNA treatment. In summary, these results suggest that EWSR1 regulates the acetylation of microtubules in a cell cycle-dependent manner through its dynamic location on spindle MTs, and may be a novel regulator for mitosis progress independent of its translocation.
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Affiliation(s)
- Yi-Long Wang
- a State Key Laboratory of Proteomics , Beijing Proteome Research Center, Beijing Institute of Radiation Medicine , Beijing , China
| | - Hui Chen
- a State Key Laboratory of Proteomics , Beijing Proteome Research Center, Beijing Institute of Radiation Medicine , Beijing , China
| | - Yi-Qun Zhan
- a State Key Laboratory of Proteomics , Beijing Proteome Research Center, Beijing Institute of Radiation Medicine , Beijing , China
| | - Rong-Hua Yin
- a State Key Laboratory of Proteomics , Beijing Proteome Research Center, Beijing Institute of Radiation Medicine , Beijing , China
| | - Chang-Yan Li
- a State Key Laboratory of Proteomics , Beijing Proteome Research Center, Beijing Institute of Radiation Medicine , Beijing , China
| | - Chang-Hui Ge
- a State Key Laboratory of Proteomics , Beijing Proteome Research Center, Beijing Institute of Radiation Medicine , Beijing , China
| | - Miao Yu
- a State Key Laboratory of Proteomics , Beijing Proteome Research Center, Beijing Institute of Radiation Medicine , Beijing , China
| | - Xiao-Ming Yang
- a State Key Laboratory of Proteomics , Beijing Proteome Research Center, Beijing Institute of Radiation Medicine , Beijing , China
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10
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Saroufim MA, Bensidoun P, Raymond P, Rahman S, Krause MR, Oeffinger M, Zenklusen D. The nuclear basket mediates perinuclear mRNA scanning in budding yeast. J Cell Biol 2016; 211:1131-40. [PMID: 26694838 PMCID: PMC4687876 DOI: 10.1083/jcb.201503070] [Citation(s) in RCA: 50] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Single-molecule resolution particle tracking reveals that mRNAs in S. cerevisiae scan the nuclear periphery before being exported to the cytoplasm and that this process is mediated by both components of the nuclear basket and the mRNP. After synthesis and transit through the nucleus, messenger RNAs (mRNAs) are exported to the cytoplasm through the nuclear pore complex (NPC). At the NPC, messenger ribonucleoproteins (mRNPs) first encounter the nuclear basket where mRNP rearrangements are thought to allow access to the transport channel. Here, we use single mRNA resolution live cell microscopy and subdiffraction particle tracking to follow individual mRNAs on their path toward the cytoplasm. We show that when reaching the nuclear periphery, RNAs are not immediately exported but scan along the nuclear periphery, likely to find a nuclear pore allowing export. Deletion or mutation of the nuclear basket proteins MLP1/2 or the mRNA binding protein Nab2 changes the scanning behavior of mRNPs at the nuclear periphery, shortens residency time at nuclear pores, and results in frequent release of mRNAs back into the nucleoplasm. These observations suggest a role for the nuclear basket in providing an interaction platform that keeps RNAs at the periphery, possibly to allow mRNP rearrangements before export.
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Affiliation(s)
- Mark-Albert Saroufim
- Departement de Biochimie et Medecine Moleculaire, Faculte de Medecine, Universite de Montreal, H3T 1J4 Montreal, Quebec, Canada
| | - Pierre Bensidoun
- Departement de Biochimie et Medecine Moleculaire, Faculte de Medecine, Universite de Montreal, H3T 1J4 Montreal, Quebec, Canada Institut de Recherches Cliniques de Montreal, H2W 1R7 Montreal, Quebec, Canada
| | - Pascal Raymond
- Departement de Biochimie et Medecine Moleculaire, Faculte de Medecine, Universite de Montreal, H3T 1J4 Montreal, Quebec, Canada
| | - Samir Rahman
- Departement de Biochimie et Medecine Moleculaire, Faculte de Medecine, Universite de Montreal, H3T 1J4 Montreal, Quebec, Canada
| | - Matthew R Krause
- Montreal Neurological Institute, McGill University, H3A 2B4 Montreal, Quebec, Canada
| | - Marlene Oeffinger
- Departement de Biochimie et Medecine Moleculaire, Faculte de Medecine, Universite de Montreal, H3T 1J4 Montreal, Quebec, Canada Institut de Recherches Cliniques de Montreal, H2W 1R7 Montreal, Quebec, Canada Faculty of Medicine, Division of Experimental Medicine, McGill University, H3A 2B4 Montreal, Quebec, Canada
| | - Daniel Zenklusen
- Departement de Biochimie et Medecine Moleculaire, Faculte de Medecine, Universite de Montreal, H3T 1J4 Montreal, Quebec, Canada
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11
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Subbotin RI, Chait BT. A pipeline for determining protein-protein interactions and proximities in the cellular milieu. Mol Cell Proteomics 2014; 13:2824-35. [PMID: 25172955 DOI: 10.1074/mcp.m114.041095] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
It remains extraordinarily challenging to elucidate endogenous protein-protein interactions and proximities within the cellular milieu. The dynamic nature and the large range of affinities of these interactions augment the difficulty of this undertaking. Among the most useful tools for extracting such information are those based on affinity capture of target bait proteins in combination with mass spectrometric readout of the co-isolated species. Although highly enabling, the utility of affinity-based methods is generally limited by difficulties in distinguishing specific from nonspecific interactors, preserving and isolating all unique interactions including those that are weak, transient, or rapidly exchanging, and differentiating proximal interactions from those that are more distal. Here, we have devised and optimized a set of methods to address these challenges. The resulting pipeline involves flash-freezing cells in liquid nitrogen to preserve the cellular environment at the moment of freezing; cryomilling to fracture the frozen cells into intact micron chunks to allow for rapid access of a chemical reagent and to stabilize the intact endogenous subcellular assemblies and interactors upon thawing; and utilizing the high reactivity of glutaraldehyde to achieve sufficiently rapid stabilization at low temperatures to preserve native cellular interactions. In the course of this work, we determined that relatively low molar ratios of glutaraldehyde to reactive amines within the cellular milieu were sufficient to preserve even labile and transient interactions. This mild treatment enables efficient and rapid affinity capture of the protein assemblies of interest under nondenaturing conditions, followed by bottom-up MS to identify and quantify the protein constituents. For convenience, we have termed this approach Stabilized Affinity Capture Mass Spectrometry. Here, we demonstrate that Stabilized Affinity Capture Mass Spectrometry allows us to stabilize and elucidate local, distant, and transient protein interactions within complex cellular milieux, many of which are not observed in the absence of chemical stabilization.
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Affiliation(s)
- Roman I Subbotin
- From the ‡The Rockefeller University 1230 York Ave, New York, New York
| | - Brian T Chait
- From the ‡The Rockefeller University 1230 York Ave, New York, New York
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12
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Kordyukova MY, Polzikov MA, Shishova KV, Zatsepina OV. Analysis of protein partners of the human nucleolar protein SURF6 in HeLa cells by a GST pull-down assay. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2014. [DOI: 10.1134/s1068162014040062] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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13
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Kordyukova MY, Polzikov MA, Shishova KV, Zatsepina OV. Functional significance of the human nucleolar protein SURF6, the key member of the SURF6 protein family in eukaryotes. DOKL BIOCHEM BIOPHYS 2014; 455:65-7. [PMID: 24795102 DOI: 10.1134/s1607672914020069] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Indexed: 01/21/2023]
Affiliation(s)
- M Yu Kordyukova
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, ul. Miklukho-Maklaya 16/10, Moscow, 117997, Russia,
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14
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Woolford JL, Baserga SJ. Ribosome biogenesis in the yeast Saccharomyces cerevisiae. Genetics 2013; 195:643-81. [PMID: 24190922 PMCID: PMC3813855 DOI: 10.1534/genetics.113.153197] [Citation(s) in RCA: 548] [Impact Index Per Article: 49.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Accepted: 08/26/2013] [Indexed: 01/09/2023] Open
Abstract
Ribosomes are highly conserved ribonucleoprotein nanomachines that translate information in the genome to create the proteome in all cells. In yeast these complex particles contain four RNAs (>5400 nucleotides) and 79 different proteins. During the past 25 years, studies in yeast have led the way to understanding how these molecules are assembled into ribosomes in vivo. Assembly begins with transcription of ribosomal RNA in the nucleolus, where the RNA then undergoes complex pathways of folding, coupled with nucleotide modification, removal of spacer sequences, and binding to ribosomal proteins. More than 200 assembly factors and 76 small nucleolar RNAs transiently associate with assembling ribosomes, to enable their accurate and efficient construction. Following export of preribosomes from the nucleus to the cytoplasm, they undergo final stages of maturation before entering the pool of functioning ribosomes. Elaborate mechanisms exist to monitor the formation of correct structural and functional neighborhoods within ribosomes and to destroy preribosomes that fail to assemble properly. Studies of yeast ribosome biogenesis provide useful models for ribosomopathies, diseases in humans that result from failure to properly assemble ribosomes.
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Affiliation(s)
- John L. Woolford
- Department of Biological Sciences, Center for Nucleic Acids Science and Technology, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213
| | - Susan J. Baserga
- Molecular Biophysics and Biochemistry, Genetics and Therapeutic Radiology, Yale University, New Haven, Connecticut 06520-8024
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15
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Thapa M, Bommakanti A, Shamsuzzaman M, Gregory B, Samsel L, Zengel JM, Lindahl L. Repressed synthesis of ribosomal proteins generates protein-specific cell cycle and morphological phenotypes. Mol Biol Cell 2013; 24:3620-33. [PMID: 24109599 PMCID: PMC3842990 DOI: 10.1091/mbc.e13-02-0097] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Cell stress caused by repression of 54 individual ribosomal genes in Saccharomyces cerevisiae is analyzed. Cell cycle progression and cell morphology responses are specific to the protein whose synthesis is repressed but bud site selection is not. Proteins that generate G2/M and G1 phenotypes map to separate areas of the ribosomal particle. The biogenesis of ribosomes is coordinated with cell growth and proliferation. Distortion of the coordinated synthesis of ribosomal components affects not only ribosome formation, but also cell fate. However, the connection between ribosome biogenesis and cell fate is not well understood. To establish a model system for inquiries into these processes, we systematically analyzed cell cycle progression, cell morphology, and bud site selection after repression of 54 individual ribosomal protein (r-protein) genes in Saccharomyces cerevisiae. We found that repression of nine 60S r-protein genes results in arrest in the G2/M phase, whereas repression of nine other 60S and 22 40S r-protein genes causes arrest in the G1 phase. Furthermore, bud morphology changes after repression of some r-protein genes. For example, very elongated buds form after repression of seven 60S r-protein genes. These genes overlap with, but are not identical to, those causing the G2/M cell cycle phenotype. Finally, repression of most r-protein genes results in changed sites of bud formation. Strikingly, the r-proteins whose repression generates similar effects on cell cycle progression cluster in the ribosome physical structure, suggesting that different topological areas of the precursor and/or mature ribosome are mechanistically connected to separate aspects of the cell cycle.
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Affiliation(s)
- Mamata Thapa
- Department of Biological Sciences, University of Maryland, Baltimore County, Baltimore, MD 21250 Flow Cytometry Core Facility, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892
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16
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Schumann Burkard G, Käser S, de Araújo PR, Schimanski B, Naguleswaran A, Knüsel S, Heller M, Roditi I. Nucleolar proteins regulate stage-specific gene expression and ribosomal RNA maturation in Trypanosoma brucei. Mol Microbiol 2013; 88:827-40. [PMID: 23617823 DOI: 10.1111/mmi.12227] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/04/2013] [Indexed: 12/20/2022]
Abstract
Different life-cycle stages of Trypanosoma brucei are characterized by stage-specific glycoprotein coats. GPEET procyclin, the major surface protein of early procyclic (insect midgut) forms, is transcribed in the nucleolus by RNA polymerase I as part of a polycistronic precursor that is processed to monocistronic mRNAs. In culture, when differentiation to late procyclic forms is triggered by removal of glycerol, the precursor is still transcribed, but accumulation of GPEET mRNA is prevented by a glycerol-responsive element in the 3' UTR. A genome-wide RNAi screen for persistent expression of GPEET in glycerol-free medium identified a novel protein, NRG1 (Nucleolar Regulator of GPEET 1), as a negative regulator. NRG1 associates with GPEET mRNA and with several nucleolar proteins. These include two PUF proteins, TbPUF7 and TbPUF10, and BOP1, a protein required for rRNA processing in other organisms. RNAi against each of these components prolonged or even increased GPEET expression in the absence of glycerol as well as causing a significant reduction in 5.8S rRNA and its immediate precursor. These results indicate that components of a complex used for rRNA maturation can have an additional role in regulating mRNAs that originate in the nucleolus.
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17
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Bonnart C, Gérus M, Hoareau-Aveilla C, Kiss T, Caizergues-Ferrer M, Henry Y, Henras AK. Mammalian HCA66 protein is required for both ribosome synthesis and centriole duplication. Nucleic Acids Res 2012; 40:6270-89. [PMID: 22434888 PMCID: PMC3401428 DOI: 10.1093/nar/gks234] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Ribosome production, one of the most energy-consuming biosynthetic activities in living cells, is adjusted to growth conditions and coordinated with the cell cycle. Connections between ribosome synthesis and cell cycle progression have been described, but the underlying mechanisms remain only partially understood. The human HCA66 protein was recently characterized as a component of the centrosome, the major microtubule-organizing center (MTOC) in mammalian cells, and was shown to be required for centriole duplication and assembly of the mitotic spindle. We show here that HCA66 is also required for nucleolar steps of the maturation of the 40S ribosomal subunit and therefore displays a dual function. Overexpression of a dominant negative version of HCA66, accumulating at the centrosome but absent from the nucleoli, alters centrosome function but has no effect on pre-rRNA processing, suggesting that HCA66 acts independently in each process. In yeast and HeLa cells, depletion of MTOC components does not impair ribosome synthesis. Hence our results suggest that both in yeast and human cells, assembly of a functional MTOC and ribosome synthesis are not closely connected processes.
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Affiliation(s)
- Chrystelle Bonnart
- Centre National de la Recherche Scientifique, Laboratoire de Biologie Moléculaire Eucaryote, Toulouse, France
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18
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Polzikov MA, Kordyukova MY, Zavalishina LE, Magoulas C, Zatsepina OV. Development of novel mouse hybridomas producing monoclonal antibodies specific to human and mouse nucleolar protein SURF-6. Hybridoma (Larchmt) 2012; 31:48-53. [PMID: 22316485 PMCID: PMC3275798 DOI: 10.1089/hyb.2011.0078] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Accepted: 10/12/2011] [Indexed: 01/09/2023]
Abstract
SURF-6 is an evolutionarily conserved nucleolar protein that is important for cell viability; however, its function in mammals still remains uncertain. The aim of this study is to generate monoclonal antibodies to human SURF-6 protein suitable for fundamental and biomedical research. The full-size human SURF-6 was expressed as a recombinant GST-fusion protein and used as an antigen to generate monoclonal antibodies, S79 and S148, specific for SURF-6. The monoclonal antibody produced by hybridoma clone S79 specifically recognizes endogenous SURF-6 by Western and immunofluorescence analyses in various cultured human cells, and by immunohistochemistry in paraffin-embedded sections of human breast cancer samples. Moreover, S79 immunoprecipitates protein complexes containing SURF-6 from HeLa cells extracts. The antibody S79 recognizes SURF-6 only in human cells; however, the antibody produced by hybridoma clone S148 can detect SURF-6 of human and mouse origin. Monoclonal antibodies to the nucleolar protein SURF-6 described in this work can be a useful tool for studies of ribosome biogenesis in normal and cancer cells.
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Affiliation(s)
- Mikhail A Polzikov
- Shemyakin-Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, 16/10 Miklukho-Maklaya, Moscow, Russia
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19
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Liu T, Deng M, Li J, Tong X, Wei Q, Ye X. Phosphorylation of right open reading frame 2 (Rio2) protein kinase by polo-like kinase 1 regulates mitotic progression. J Biol Chem 2011; 286:36352-60. [PMID: 21880710 PMCID: PMC3196107 DOI: 10.1074/jbc.m111.250175] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2011] [Revised: 08/19/2011] [Indexed: 01/25/2023] Open
Abstract
Polo-like kinase 1 (Plk1) plays essential roles during multiple stages of mitosis by phosphorylating a number of substrates. Here, we report that the atypical protein kinase Rio2 is a novel substrate of Plk1 and can be phosphorylated by Plk1 at Ser-335, Ser-380, and Ser-548. Overexpression of Rio2 causes a prolonged mitotic exit whereas knockdown of Rio2 accelerates mitotic progression, suggesting that Rio2 is required for the proper mitotic progression. Overexpression of phospho-mimicking mutant Rio2 S3D but not the nonphosphorylatable mutant Rio2 S3A displays a profile similar to that of wild-type Rio2. These results indicate that the phosphorylation status of Rio2 correlates with its function in mitosis. Furthermore, time-lapse imaging data show that overexpression of Rio2 but not Rio2 S3A results in a slowed metaphase-anaphase transition. Collectively, these findings strongly indicate that the Plk1-mediated phosphorylation of Rio2 regulates metaphase-anaphase transition during mitotic progression.
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Affiliation(s)
- Ting Liu
- From the Center for Molecular Immunology, Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China and
- the Graduate University of the Chinese Academy of Sciences, Beijing 100101, China
| | - Min Deng
- From the Center for Molecular Immunology, Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China and
- the Graduate University of the Chinese Academy of Sciences, Beijing 100101, China
| | - Junhui Li
- From the Center for Molecular Immunology, Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China and
- the Graduate University of the Chinese Academy of Sciences, Beijing 100101, China
| | - Xiaomei Tong
- From the Center for Molecular Immunology, Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China and
| | - Qian Wei
- From the Center for Molecular Immunology, Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China and
- the Graduate University of the Chinese Academy of Sciences, Beijing 100101, China
| | - Xin Ye
- From the Center for Molecular Immunology, Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China and
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20
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Kutuzov MA, Andreeva AV. Prediction of biological functions of Shewanella-like protein phosphatases (Shelphs) across different domains of life. Funct Integr Genomics 2011; 12:11-23. [DOI: 10.1007/s10142-011-0254-z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2011] [Revised: 09/07/2011] [Accepted: 09/13/2011] [Indexed: 12/12/2022]
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21
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Smith SB, Kiss DL, Turk E, Tartakoff AM, Andrulis ED. Pronounced and extensive microtubule defects in a Saccharomyces cerevisiae DIS3 mutant. Yeast 2011; 28:755-69. [PMID: 21919057 DOI: 10.1002/yea.1899] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Revised: 06/21/2011] [Accepted: 07/10/2011] [Indexed: 11/05/2022] Open
Abstract
Subunits of the RNA processing exosome assemble into structurally distinct protein complexes that function in disparate cellular compartments and RNA metabolic pathways. Here, in a genetic, cell biological and transcriptomic analysis, we examined the role of Dis3, an essential polypeptide with endo- and 3'→5' exo-ribonuclease activity, in cell cycle progression. We present several lines of evidence that perturbation of DIS3 affects microtubule (MT) localization and structure in Saccharomyces cerevisiae. Cells with a DIS3 mutant: (a) accumulate anaphase and pre-anaphase mitotic spindles; (b) exhibit spindles that are misorientated and displaced from the bud neck; (c) harbour elongated spindle-associated astral MTs; (d) have an increased G1 astral MT length and number; and (e) are hypersensitive to MT poisons. Mutations in the core exosome genes RRP4 and MTR3 and the exosome cofactor gene MTR4, but not other exosome subunit gene mutants, also elicit MT phenotypes. RNA deep sequencing analysis (RNA-seq) shows broad changes in the levels of cell cycle- and MT-related transcripts in mutant strains. Collectively, the data presented in this study suggest an evolutionarily conserved role for Dis3 in linking RNA metabolism, MTs and cell cycle progression.
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Affiliation(s)
- Sarah B Smith
- Department of Molecular Biology and Microbiology, Case Comprehensive Cancer Center, Case Western Reserve University School of Medicine, Cleveland, OH 44106, USA
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Ribosome synthesis-unrelated functions of the preribosomal factor Rrp12 in cell cycle progression and the DNA damage response. Mol Cell Biol 2011; 31:2422-38. [PMID: 21482668 DOI: 10.1128/mcb.05343-11] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Given the high metabolic cost required to generate ribosomes, it has been assumed that proteins involved in ribosome synthesis might establish functional cross talk with other intracellular processes to efficiently couple ribosome production and cell growth. However, such interconnections have remained elusive due to the difficulty in separating the intra- and extraribosomal roles of ribosome biogenesis factors. Using a yeast functional screen, I have discovered that Rrp12, a conserved protein involved in ribosome maturation and export, plays roles in the cell cycle and the DNA damage response. These results indicate that Rrp12 participates in a karyopherin Kap121-dependent import route that is crucial for nuclear sequestration of ribonucleotide reductase subunits and, thereby, ensures the proper kinetics of deoxyribonucleotide production during the cell cycle. Within this route, Rrp12 acts as a cofactor important for the full functionality of Kap121. This activity is mechanistically different from the known roles of Rrp12 in ribosome biogenesis. I propose that the functional duality of Rrp12 may couple the control of ribosome production to the regulation of other cellular processes during cell cycle progression.
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23
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Polzikov MA, Veĭko NN, Zharskaia OO, Magoulas KB, Zatsepina OV. [Overexpression of the nucleolar protein SURF-6 in mouse fibroblasts NIH/3T3 leads to stabilisation of intragenic transcribed spacers of the pre-rRNA]. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2010; 36:661-71. [PMID: 21063453 DOI: 10.1134/s1068162010050092] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
SURF-6 is an evolutionary conserved nucleolar protein that is required for maintenance of cell viability, but its functional significance in mammals still remains illusive. In the present work we examined effects of SURF-6 overexpression in mouse NIH/3T3 fibroblasts transfected with two plasmids. The plasmid pUHrT62-1 encodes a tetracycline-dependant trans-activator, the protein rtTA, the plasmid pBI-SURF6--the genes of EGFP (enhanced green fluorescent protein) and of mouse SURF-6 which expression was controlled by the rtTA-responsive bi-directorial promoter. Western blot analysis showed that the SURF-6 level was severely augmented in cells transfected with pUHrT62-1 and pBI-SURF6 and incubated with the inducer--doxycycline opposed to the transfected but not-induced cells. The increase of SURF-6 was observed in 24 and 48 h after adding the inducer doxycycline. Dot-hybridization of isolated RNA with biotinilated oligonucleotide probes to various regions of mouse primarily pre-rRNA transcripts showed that overexpression of SURF-6 enhanced levels of the second intragenic transcribed spacer ITS2 in about seven folds and of the 5' external transcribed spacer 5'ETS in two folds. Amounts of fragments corresponding to 18S, 5.8S and 28S rRNA remained almost unchanged. These observations for the first time demonstrated that mammalian SURF-6 helps to stabilize or prevents premature cleavage of the pre-rRNA intragenic transcribed spacers, particularly of ITS2, similar to its homologue in S. cerevisiae the protein Rrp14. Today metazoan proteins that play a similar role in ribosome biogenesis, are not described.
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Jeon S, Kim J. Upstream open reading frames regulate the cell cycle-dependent expression of the RNA helicase Rok1 in Saccharomyces cerevisiae. FEBS Lett 2010; 584:4593-8. [PMID: 20969870 DOI: 10.1016/j.febslet.2010.10.019] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2010] [Revised: 09/09/2010] [Accepted: 10/12/2010] [Indexed: 12/13/2022]
Abstract
The RNA helicase Rok1 plays a role in rRNA processing and in control of cell cycle progression in Saccharomyces cerevisiae. We identified two upstream open reading frames (uORFs) within the ROK1 5' untranslated region, which inhibited Rok1 translation. Mutating uATG to uAAG or generation of a premature stop codon in the uORFs resulted in increased Rok1p levels. Rok1 protein levels oscillated during the cell cycle, declining at G1/S and increasing at G2. The uAAG1 mutation caused a constitutive level of Rok1 proteins throughout the cell cycle, resulting in significant delays in mitotic bud emergence and recovery from pheromone arrest. Our study reveals that the Rok1 protein level is regulated by uORFs, which is critical in cell cycle progression.
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Affiliation(s)
- Soonmee Jeon
- Department of Microbiology and Molecular Biology, College of Biosciences and Biotechnology, Chungnam National University, Daejeon 305-764, Republic of Korea
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25
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Hussain S, Benavente SB, Nascimento E, Dragoni I, Kurowski A, Gillich A, Humphreys P, Frye M. The nucleolar RNA methyltransferase Misu (NSun2) is required for mitotic spindle stability. ACTA ACUST UNITED AC 2009; 186:27-40. [PMID: 19596847 PMCID: PMC2712989 DOI: 10.1083/jcb.200810180] [Citation(s) in RCA: 114] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Myc-induced SUN domain–containing protein (Misu or NSun2) is a nucleolar RNA methyltransferase important for c-Myc–induced proliferation in skin, but the mechanisms by which Misu contributes to cell cycle progression are unknown. In this study, we demonstrate that Misu translocates from the nucleoli in interphase to the spindle in mitosis as an RNA–protein complex that includes 18S ribosomal RNA. Functionally, depletion of Misu caused multiple mitotic defects, including formation of unstructured spindles, multipolar spindles, and chromosome missegregation, leading to aneuploidy and cell death. The presence of both RNA and Misu is required for correct spindle assembly, and this process is independent of active translation. Misu might mediate its function at the spindle by recruiting nucleolar and spindle-associated protein (NuSAP), an essential microtubule-stabilizing and bundling protein. We further identify NuSAP as a novel direct target gene of c-Myc. Collectively, our results suggest a novel mechanism by which c-Myc promotes proliferation by stabilizing the mitotic spindle in fast-dividing cells via Misu and NuSAP.
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Affiliation(s)
- Shobbir Hussain
- Wellcome Trust Centre for Stem Cell Research, University of Cambridge, England, UK
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26
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Valouev IA, Fominov GV, Sokolova EE, Smirnov VN, Ter-Avanesyan MD. Elongation factor eEF1B modulates functions of the release factors eRF1 and eRF3 and the efficiency of translation termination in yeast. BMC Mol Biol 2009; 10:60. [PMID: 19545407 PMCID: PMC2705663 DOI: 10.1186/1471-2199-10-60] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Accepted: 06/22/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Termination of translation in eukaryotes is controlled by two interacting polypeptide chain release factors, eRF1 and eRF3. While eRF1 recognizes nonsense codons, eRF3 facilitates polypeptide chain release from the ribosome in a GTP-dependent manner. Besides termination, both release factors have essential, but poorly characterized functions outside of translation. RESULTS To characterize further the functions of yeast eRF1 and eRF3, a genetic screen for their novel partner proteins was performed. As a result, the genes for gamma (TEF4 and TEF3/CAM1) and alpha (TEF5/EFB1) subunits of the translation elongation factor eEF1B, known to catalyze the exchange of bound GDP for GTP on eEF1A, were revealed. These genes act as dosage suppressors of a synthetic growth defect caused by some mutations in the SUP45 and SUP35 genes encoding eRF1 and eRF3, respectively. Extra copies of TEF5 and TEF3 can also suppress the temperature sensitivity of some sup45 and sup35 mutants and reduce nonsense codon readthrough caused by these omnipotent suppressors. Besides, overproduction of eEF1Balpha reduces nonsense codon readthrough in the strain carrying suppressor tRNA. Such effects were not shown for extra copies of TEF2, which encodes eEF1A, thus indicating that they were not due to eEF1A activation. CONCLUSION The data obtained demonstrate involvement of the translation elongation factor eEF1B in modulating the functions of translation termination factors and suggest its possible role in GDP for GTP exchange on eRF3.
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27
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Burroughs L, Woolfrey A, Shimamura A. Shwachman-Diamond syndrome: a review of the clinical presentation, molecular pathogenesis, diagnosis, and treatment. Hematol Oncol Clin North Am 2009; 23:233-48. [PMID: 19327581 DOI: 10.1016/j.hoc.2009.01.007] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Shwachman-Diamond syndrome is a rare autosomal-recessive, multisystem disease characterized by exocrine pancreatic insufficiency, impaired hematopoiesis, and leukemia predisposition. Other clinical features include skeletal, immunologic, hepatic, and cardiac disorders. This article focuses on the clinical presentation, diagnostic work-up, clinical management, and treatment of patients with Shwachman-Diamond syndrome.
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Affiliation(s)
- Lauri Burroughs
- Clinical Research Division, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, D1-100, PO Box 19024, Seattle, WA 98109-1024, USA.
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Leemann-Zakaryan RP, Pahlich S, Sedda MJ, Quero L, Grossenbacher D, Gehring H. Dynamic subcellular localization of the Ewing sarcoma proto-oncoprotein and its association with and stabilization of microtubules. J Mol Biol 2008; 386:1-13. [PMID: 19133275 DOI: 10.1016/j.jmb.2008.12.039] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2008] [Revised: 12/12/2008] [Accepted: 12/12/2008] [Indexed: 11/27/2022]
Abstract
The Ewing sarcoma (EWS) protein is a member of a large family of RNA-binding proteins. Chimeric EWS oncoproteins generated by chromosomal translocations between the EWS protein and several transcription factors cause various malignant tumors. Due to its multifunctional properties, the EWS protein is involved in such processes as meiotic DNA pairing/recombination, cellular senescence, gene expression, RNA processing and transport, and cell signaling. The EWS protein is predominantly located in the nucleus. It was found in the cytoplasm and associated with the cell membrane. In this study, analysis of the localization of endogenous and fluorescently labeled recombinant EWS protein in different phases of the cell cycle in different cell lines revealed a very dynamic subcellular distribution of the EWS protein. In Cos7 and HeLa cells, an association of the EWS protein with the centrosomal compartments was shown. Furthermore, in HEK (human embryonic kidney)-293 (T) cells, an interaction of the overexpressed recombinant EWS-yellow fluorescent protein fusion protein with microtubules, leading to their stabilization and cell cycle arrest, was demonstrated. As an outlook, the present findings provide an important insight into temporally and spatially regulated functions of the EWS protein and, particularly, into its role in the regulation of the cell cycle and possibly cell differentiation.
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Segerstolpe A, Lundkvist P, Osheim YN, Beyer AL, Wieslander L. Mrd1p binds to pre-rRNA early during transcription independent of U3 snoRNA and is required for compaction of the pre-rRNA into small subunit processomes. Nucleic Acids Res 2008; 36:4364-80. [PMID: 18586827 PMCID: PMC2490760 DOI: 10.1093/nar/gkn384] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In Saccharomyces cerevisiae, synthesis of the small ribosomal subunit requires assembly of the 35S pre-rRNA into a 90S preribosomal complex. SnoRNAs, including U3 snoRNA, and many trans-acting proteins are required for the ordered assembly and function of the 90S preribosomal complex. Here, we show that the conserved protein Mrd1p binds to the pre-rRNA early during transcription and is required for compaction of the pre-18S rRNA into SSU processome particles. We have exploited the fact that an Mrd1p-GFP fusion protein is incorporated into the 90S preribosomal complex, where it acts as a partial loss-of-function mutation. When associated with the pre-rRNA, Mrd1p-GFP functionally interacts with the essential Pwp2, Mpp10 and U3 snoRNP subcomplexes that are functionally interconnected in the 90S preribosomal complex. The fusion protein can partially support 90S preribosome-mediated cleavages at the A0–A2 sites. At the same time, on a substantial fraction of transcripts, the composition and/or structure of the 90S preribosomal complex is perturbed by the fusion protein in such a way that cleavage of the 35S pre-rRNA is either blocked or shifted to aberrant sites. These results show that Mrd1p is required for establishing productive structures within the 90S preribosomal complex.
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Affiliation(s)
- Asa Segerstolpe
- Department of Molecular Biology and Functional Genomics, Stockholm University, SE-106 91, Stockholm, Sweden
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Austin KM, Gupta ML, Coats SA, Tulpule A, Mostoslavsky G, Balazs AB, Mulligan RC, Daley G, Pellman D, Shimamura A. Mitotic spindle destabilization and genomic instability in Shwachman-Diamond syndrome. J Clin Invest 2008; 118:1511-8. [PMID: 18324336 DOI: 10.1172/jci33764] [Citation(s) in RCA: 102] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2007] [Accepted: 01/30/2008] [Indexed: 01/21/2023] Open
Abstract
Deficiencies in the SBDS gene result in Shwachman-Diamond syndrome (SDS), an inherited bone marrow failure syndrome associated with leukemia predisposition. SBDS encodes a highly conserved protein previously implicated in ribosome biogenesis. Using human primary bone marrow stromal cells (BMSCs), lymphoblasts, and skin fibroblasts, we show that SBDS stabilized the mitotic spindle to prevent genomic instability. SBDS colocalized with the mitotic spindle in control primary BMSCs, lymphoblasts, and skin fibroblasts and bound to purified microtubules. Recombinant SBDS protein stabilized microtubules in vitro. We observed that primary BMSCs and lymphoblasts from SDS patients exhibited an increased incidence of abnormal mitoses. Similarly, depletion of SBDS by siRNA in human skin fibroblasts resulted in increased mitotic abnormalities and aneuploidy that accumulated over time. Treatment of primary BMSCs and lymphoblasts from SDS patients with nocodazole, a microtubule destabilizing agent, led to increased mitotic arrest and apoptosis, consistent with spindle destabilization. Conversely, SDS patient cells were resistant to taxol, a microtubule stabilizing agent. These findings suggest that spindle instability in SDS contributes to bone marrow failure and leukemogenesis.
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Affiliation(s)
- Karyn M Austin
- Department of Pediatric Hematology, Children's Hospital Boston, Boston, Massachusetts, USA
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Yamada H, Horigome C, Okada T, Shirai C, Mizuta K. Yeast Rrp14p is a nucleolar protein involved in both ribosome biogenesis and cell polarity. RNA (NEW YORK, N.Y.) 2007; 13:1977-87. [PMID: 17804645 PMCID: PMC2040088 DOI: 10.1261/rna.553807] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
We previously cloned RRP14/YKL082c, whose product exhibits two-hybrid interaction with Ebp2p, a regulatory factor of assembly of 60S ribosomal subunits. Depletion of Rrp14p results in shortage of 60S ribosomal subunits and retardation of processing from 27S pre-rRNA to 25S rRNA. Furthermore, 35S pre-rRNA synthesis appears to decline in Rrp14p-depleted cells. Rrp14p interacts with regulatory factors of 60S subunit assembly and also with Utp11p and Faf1p, which are regulatory factors required for assembly of 40S ribosomal subunits. We propose that Rrp14p is involved in ribosome synthesis from the beginning of 35S pre-rRNA synthesis to assembly of the 60S ribosomal subunit. Disruption of RRP14 causes an extremely slow growth rate of the cell, a severe defect in ribosome synthesis, and a depolarized localization of cortical actin patches throughout the cell cycle. These results suggest that Rrp14p has dual functions in ribosome synthesis and polarized cell growth.
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Affiliation(s)
- Hiroko Yamada
- Department of Biofunctional Science and Technology, Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima, Japan
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32
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Current awareness on yeast. Yeast 2007. [DOI: 10.1002/yea.1575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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Rosado IV, Kressler D, de la Cruz J. Functional analysis of Saccharomyces cerevisiae ribosomal protein Rpl3p in ribosome synthesis. Nucleic Acids Res 2007; 35:4203-13. [PMID: 17569673 PMCID: PMC1919493 DOI: 10.1093/nar/gkm388] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Ribosome synthesis in eukaryotes requires a multitude of trans-acting factors. These factors act at many steps as the pre-ribosomal particles travel from the nucleolus to the cytoplasm. In contrast to the well-studied trans-acting factors, little is known about the contribution of the ribosomal proteins to ribosome biogenesis. Herein, we have analysed the role of ribosomal protein Rpl3p in 60S ribosomal subunit biogenesis. In vivo depletion of Rpl3p results in a deficit in 60S ribosomal subunits and the appearance of half-mer polysomes. This phenotype is likely due to the instability of early and intermediate pre-ribosomal particles, as evidenced by the low steady-state levels of 27SA3, 27SBS and 7SL/S precursors. Furthermore, depletion of Rpl3p impairs the nucleocytoplasmic export of pre-60S ribosomal particles. Interestingly, flow cytometry analysis indicates that Rpl3p-depleted cells arrest in the G1 phase. Altogether, we suggest that upon depletion of Rpl3p, early assembly of 60S ribosomal subunits is aborted and subsequent steps during their maturation and export prevented.
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Affiliation(s)
- Iván V. Rosado
- Departamento de Genética, Universidad de Sevilla, Sevilla, Spain and Biochemie-Zentrum der Universität Heidelberg, Heidelberg, Germany
| | - Dieter Kressler
- Departamento de Genética, Universidad de Sevilla, Sevilla, Spain and Biochemie-Zentrum der Universität Heidelberg, Heidelberg, Germany
| | - Jesús de la Cruz
- Departamento de Genética, Universidad de Sevilla, Sevilla, Spain and Biochemie-Zentrum der Universität Heidelberg, Heidelberg, Germany
- *To whom correspondence should be addressed. +34 95 455 71 06+34 95 455 71 04
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Martín-Marcos P, Hinnebusch AG, Tamame M. Ribosomal protein L33 is required for ribosome biogenesis, subunit joining, and repression of GCN4 translation. Mol Cell Biol 2007; 27:5968-85. [PMID: 17548477 PMCID: PMC1952170 DOI: 10.1128/mcb.00019-07] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We identified a mutation in the 60S ribosomal protein L33A (rpl33a-G76R) that elicits derepression of GCN4 translation (Gcd- phenotype) by allowing scanning preinitiation complexes to bypass inhibitory upstream open reading frame 4 (uORF4) independently of prior uORF1 translation and reinitiation. At 37 degrees C, rpl33a-G76R confers defects in 60S biogenesis comparable to those produced by the deletion of RPL33A (DeltaA). At 28 degrees C, however, the 60S biogenesis defect is less severe in rpl33a-G76R than in DeltaA cells, yet rpl33a-G76R confers greater derepression of GCN4 and a larger reduction in general translation. Hence, it appears that rpl33a-G76R has a stronger effect on ribosomal-subunit joining than does a comparable reduction of wild-type 60S levels conferred by DeltaA. We suggest that rpl33a-G76R alters the 60S subunit in a way that impedes ribosomal-subunit joining and thereby allows 48S rRNA complexes to abort initiation at uORF4, resume scanning, and initiate downstream at GCN4. Because overexpressing tRNAiMet suppresses the Gcd- phenotype of rpl33a-G76R cells, dissociation of tRNAiMet from the 40S subunit may be responsible for abortive initiation at uORF4 in this mutant. We further demonstrate that rpl33a-G76R impairs the efficient processing of 35S and 27S pre-rRNAs and reduces the accumulation of all four mature rRNAs, indicating an important role for L33 in the biogenesis of both ribosomal subunits.
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Affiliation(s)
- Pilar Martín-Marcos
- Instituto de Microbiología Bioquímica, CSIC/Universidad de Salamanca, Edificio Departamental de Biología, Campus Miguel de Unamuno, 37007 Salamanca, Spain
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