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Westover KR, Jin P, Yao B. Bridging the gap: R-loop mediated genomic instability and its implications in neurological diseases. Epigenomics 2024; 16:589-608. [PMID: 38530068 PMCID: PMC11160457 DOI: 10.2217/epi-2023-0379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Accepted: 03/12/2024] [Indexed: 03/27/2024] Open
Abstract
R-loops, intricate three-stranded structures formed by RNA-DNA hybrids and an exposed non-template DNA strand, are fundamental to various biological phenomena. They carry out essential and contrasting functions within cellular mechanisms, underlining their critical role in maintaining cellular homeostasis. The specific cellular context that dictates R-loop formation determines their function, particularly emphasizing the necessity for their meticulous genomic regulation. Notably, the aberrant formation or misregulation of R-loops is implicated in numerous neurological disorders. This review focuses on the complex interactions between R-loops and double-strand DNA breaks, exploring how R-loop dysregulation potentially contributes to the pathogenesis of various brain disorders, which could provide novel insights into the molecular mechanisms underpinning neurological disease progression and identify potential therapeutic targets by highlighting these aspects.
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Affiliation(s)
- Katherine R Westover
- Department of Human Genetics, Emory University, School of Medicine, Atlanta, GA 30322, USA
| | - Peng Jin
- Department of Human Genetics, Emory University, School of Medicine, Atlanta, GA 30322, USA
| | - Bing Yao
- Department of Human Genetics, Emory University, School of Medicine, Atlanta, GA 30322, USA
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2
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McLaurin DM, Tucker SK, Hebert MD. Coilin mediates m6A RNA methylation through phosphorylation of METTL3. Biol Open 2023; 12:bio060116. [PMID: 38050869 PMCID: PMC10714142 DOI: 10.1242/bio.060116] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Accepted: 11/14/2023] [Indexed: 12/07/2023] Open
Abstract
MicroRNAs (miRNAs) are a class of noncoding RNAs that regulate gene expression. An important step in miRNA biogenesis occurs when primary miRNAs are bound and cleaved by the microprocessor to generate precursor miRNAs. Regulation at this step is essential and one such regulator includes m6A RNA methylation, an RNA modification found on primary miRNAs that is installed by METTL3 and bound by hnRNPA2B1. Our lab has recently discovered that the Cajal body marker protein coilin also participates in miRNA biogenesis and hypothesized that coilin may be influencing miRNA biogenesis through m6A RNA methylation. Here we report that coilin suppression reduces m6A on primary Let7a and miR-21. We also found that coilin suppression reduced the protein expression of hnRNPA2B1 and METTL3. We observed an interaction between coilin and ectopically expressed METTL3 and found that coilin suppression reduced the nucleoplasmic portion of METTL3 and blunted ectopic METTL3 phosphorylation. Finally, coilin suppression disrupted the greater METTL3 complex with cofactors METTL14 and WTAP. Collectively, our work has uncovered a role for coilin in mediating m6A RNA methylation and provides an avenue by which coilin participates in miRNA biogenesis.
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Affiliation(s)
- Douglas M. McLaurin
- Department of Cell and Molecular Biology, The University of Mississippi Medical Center, Jackson, MS 39216-4505, USA
| | - Sara K. Tucker
- Department of Cell and Molecular Biology, The University of Mississippi Medical Center, Jackson, MS 39216-4505, USA
| | - Michael D. Hebert
- Department of Cell and Molecular Biology, The University of Mississippi Medical Center, Jackson, MS 39216-4505, USA
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3
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White L, Erbay B, Blair GE. The Cajal body protein p80-coilin forms a complex with the adenovirus L4-22K protein and facilitates the nuclear export of adenovirus mRNA. mBio 2023; 14:e0145923. [PMID: 37795984 PMCID: PMC10653806 DOI: 10.1128/mbio.01459-23] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Accepted: 08/11/2023] [Indexed: 10/06/2023] Open
Abstract
IMPORTANCE The architecture of sub-nuclear structures of eucaryotic cells is often changed during the infectious cycle of many animal and plant viruses. Cajal bodies (CBs) form a major sub-nuclear structure whose functions may include the regulation of cellular RNA metabolism. During the lifecycle of human adenovirus 5 (Ad5), CBs are reorganized from their spherical-like structure into smaller clusters termed microfoci. The mechanism of this reorganization and its significance for virus replication has yet to be established. Here we show that the major CB protein, p80-coilin, facilitates the nuclear export of Ad5 transcripts. Depletion of p80-coilin by RNA interference led to lowered levels of viral proteins and infectious virus. p80-coilin was found to form a complex with the viral L4-22K protein in Ad5-infected cells and in some reorganized microfoci. These findings assign a new role for p80-coilin as a potential regulator of infection by a human DNA virus.
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Affiliation(s)
- Laura White
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - Bilgi Erbay
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
| | - G. Eric Blair
- School of Molecular and Cellular Biology, Faculty of Biological Sciences, University of Leeds, Leeds, United Kingdom
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4
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Bergstrand S, O'Brien EM, Coucoravas C, Hrossova D, Peirasmaki D, Schmidli S, Dhanjal S, Pederiva C, Siggens L, Mortusewicz O, O'Rourke JJ, Farnebo M. Small Cajal body-associated RNA 2 (scaRNA2) regulates DNA repair pathway choice by inhibiting DNA-PK. Nat Commun 2022; 13:1015. [PMID: 35197472 PMCID: PMC8866460 DOI: 10.1038/s41467-022-28646-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Accepted: 01/25/2022] [Indexed: 12/20/2022] Open
Abstract
Evidence that long non-coding RNAs (lncRNAs) participate in DNA repair is accumulating, however, whether they can control DNA repair pathway choice is unknown. Here we show that the small Cajal body-specific RNA 2 (scaRNA2) can promote HR by inhibiting DNA-dependent protein kinase (DNA-PK) and, thereby, NHEJ. By binding to the catalytic subunit of DNA-PK (DNA-PKcs), scaRNA2 weakens its interaction with the Ku70/80 subunits, as well as with the LINP1 lncRNA, thereby preventing catalytic activation of the enzyme. Inhibition of DNA-PK by scaRNA2 stimulates DNA end resection by the MRN/CtIP complex, activation of ATM at DNA lesions and subsequent repair by HR. ScaRNA2 is regulated in turn by WRAP53β, which binds this RNA, sequestering it away from DNA-PKcs and allowing NHEJ to proceed. These findings reveal that RNA-dependent control of DNA-PK catalytic activity is involved in regulating whether the cell utilizes NHEJ or HR. Proper repair of DNA double-strand breaks is essential for genomic stability. Here, the authors report that a long non-coding RNA, scaRNA2, inhibits DNA-PK and thereby regulates the choice between error-prone NHEJ and error-free HR DNA repair.
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Affiliation(s)
- Sofie Bergstrand
- Department of Biosciences and Nutrition, Neo, Karolinska Institutet, Stockholm, Sweden
| | - Eleanor M O'Brien
- Department of Cell and Molecular biology, Biomedicum, Karolinska Institutet, Stockholm, Sweden
| | - Christos Coucoravas
- Department of Cell and Molecular biology, Biomedicum, Karolinska Institutet, Stockholm, Sweden
| | - Dominika Hrossova
- Department of Cell and Molecular biology, Biomedicum, Karolinska Institutet, Stockholm, Sweden
| | - Dimitra Peirasmaki
- Department of Cell and Molecular biology, Biomedicum, Karolinska Institutet, Stockholm, Sweden
| | - Sandro Schmidli
- Department of Cell and Molecular biology, Biomedicum, Karolinska Institutet, Stockholm, Sweden
| | - Soniya Dhanjal
- Department of Cell and Molecular biology, Biomedicum, Karolinska Institutet, Stockholm, Sweden
| | - Chiara Pederiva
- Department of Cell and Molecular biology, Biomedicum, Karolinska Institutet, Stockholm, Sweden
| | - Lee Siggens
- Department of Biosciences and Nutrition, Neo, Karolinska Institutet, Stockholm, Sweden
| | - Oliver Mortusewicz
- Department of Oncology and Pathology, SciLife, Karolinska Institutet, Stockholm, Sweden
| | - Julienne J O'Rourke
- Department of Cell and Molecular biology, Biomedicum, Karolinska Institutet, Stockholm, Sweden
| | - Marianne Farnebo
- Department of Biosciences and Nutrition, Neo, Karolinska Institutet, Stockholm, Sweden. .,Department of Cell and Molecular biology, Biomedicum, Karolinska Institutet, Stockholm, Sweden.
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5
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Abbasi S, Schild-Poulter C. Identification of Ku70 Domain-Specific Interactors Using BioID2. Cells 2021; 10:cells10030646. [PMID: 33799447 PMCID: PMC8001828 DOI: 10.3390/cells10030646] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Revised: 03/04/2021] [Accepted: 03/10/2021] [Indexed: 11/23/2022] Open
Abstract
Since its inception, proximity-dependent biotin identification (BioID), an in vivo biochemical screening method to identify proximal protein interactors, has seen extensive developments. Improvements and variants of the original BioID technique are being reported regularly, each expanding upon the existing potential of the original technique. While this is advancing our capabilities to study protein interactions under different contexts, we have yet to explore the full potential of the existing BioID variants already at our disposal. Here, we used BioID2 in an innovative manner to identify and map domain-specific protein interactions for the human Ku70 protein. Four HEK293 cell lines were created, each stably expressing various BioID2-tagged Ku70 segments designed to collectively identify factors that interact with different regions of Ku70. Historically, although many interactions have been mapped to the C-terminus of the Ku70 protein, few have been mapped to the N-terminal von Willebrand A-like domain, a canonical protein-binding domain ideally situated as a site for protein interaction. Using this segmented approach, we were able to identify domain-specific interactors as well as evaluate advantages and drawbacks of the BioID2 technique. Our study identifies several potential new Ku70 interactors and validates RNF113A and Spindly as proteins that contact or co-localize with Ku in a Ku70 vWA domain-specific manner.
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Yue ZX, Gao RQ, Gao C, Liu SG, Zhao XX, Xing TY, Niu J, Li ZG, Zheng HY, Ding W. The prognostic potential of coilin in association with p27 expression in pediatric acute lymphoblastic leukemia for disease relapse. Cancer Cell Int 2018; 18:106. [PMID: 30065619 PMCID: PMC6062948 DOI: 10.1186/s12935-018-0600-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2018] [Accepted: 07/18/2018] [Indexed: 12/20/2022] Open
Abstract
Background Cajal body (CB) is a nucleic organelle where small nuclear ribonucleoproteins undergo modification, maturation, splicing and/or assembly. Coilin is the marker structural protein of CBs. The expression level and cellular localization of coilin is sensitive to chemotherapeutic reagents, such as cisplatin. The gene of cyclin-dependent kinase inhibitor 1B (p27) is located with a high incidence translocation region of leukemic chromosomes, and its expression was of prognosis values in a variety of adult leukemia types. The exact profile and associated functions of coilin, as well as p27, in children’s acute lymphoblastic leukemia (ALL) is obscure. Methods Bone marrow samples from 144 patients with ALL were collected. The expression levels of coilin and p27 were detected by qRT-PCR. The patient cohort was divided into low and high groups of coilin and p27 respectively. The prognosis and clinicobiological characteristics of different groups were investigated, especially focused on the treatment outcome. Leukemia cells of Reh or RS4;11 were exposed to different concentrations of DNR, prior to the detection for morphological changes of coilin by immunofluorescence. In Reh cells, lentivirus sh-coilin was used to silence coilin expression. Western blotting was used to detect coilin and p27 expression; flow cytometry was used for cell cycle and apoptosis assay; MTS method was used for measuring cell viability to examine the drug sensitivity of DNR. Results In this study, we found that daunorubicin was able to induce significant morphological changes of CBs in Reh and RS4;11 cells. Knockdown the expression of coilin increased the sensitivity to daunorubicin and inhibited the expression of p27 in Reh cells, and led to increased apoptosis. Importantly, not only the levels of coilin and p27 mRNA expression at initial diagnosis ALL children are markedly higher than those at complete remission (CR), but also both coilin and p27 expression in the relapsed patients was observed significantly higher comparing to the continuous CR patients. The 4-year EFS and RFS indicated that low levels of both coilin and p27 group favored better prognosis (p < 0.05). Conclusions Our results indicated that consideration of coilin and p27 levels could be a prognostic reference for predicting the outcome of pediatric ALL patients, especially for disease recurrence. Reduction of coilin expression was sufficient to increase the sensitivity of leukemic cells to daunorubicin treatments, and during which possibly involved functions of p27 in cell cycle regulation and its effects on cell apoptosis.
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Affiliation(s)
- Zhi-Xia Yue
- 1Department of Medical Genetics and Developmental Biology, School of Basic Medical Sciences, Capital Medical University, Beijing, 100069 China.,Beijing Key Laboratory of Pediatric Hematology Oncology, National Key Discipline of Pediatrics, Ministry of Education, MOE Key Laboratory of Major Diseases in Children, Hematology Oncology Center, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing, 100045 China
| | - Rui-Qi Gao
- 3Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, Beijing, 100069 China
| | - Chao Gao
- Beijing Key Laboratory of Pediatric Hematology Oncology, National Key Discipline of Pediatrics, Ministry of Education, MOE Key Laboratory of Major Diseases in Children, Hematology Oncology Center, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing, 100045 China
| | - Shu-Guang Liu
- Beijing Key Laboratory of Pediatric Hematology Oncology, National Key Discipline of Pediatrics, Ministry of Education, MOE Key Laboratory of Major Diseases in Children, Hematology Oncology Center, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing, 100045 China
| | - Xiao-Xi Zhao
- Beijing Key Laboratory of Pediatric Hematology Oncology, National Key Discipline of Pediatrics, Ministry of Education, MOE Key Laboratory of Major Diseases in Children, Hematology Oncology Center, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing, 100045 China
| | - Tian-Yu Xing
- Beijing Key Laboratory of Pediatric Hematology Oncology, National Key Discipline of Pediatrics, Ministry of Education, MOE Key Laboratory of Major Diseases in Children, Hematology Oncology Center, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing, 100045 China
| | - Jing Niu
- 3Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, Beijing, 100069 China.,4Beijing Key Laboratory for Tumor Invasion and Metastasis Research, Cancer Institute of Capital Medical University, Beijing, 100069 China
| | - Zhi-Gang Li
- Key Laboratory of Major Diseases in Children (Capital Medical University), Ministry of Education, National Key Discipline of Pediatrics, Ministry of Education, Hematology Center, Beijing Children's Hospital, Capital Medical University, Beijing, 100045 China
| | - Hu-Yong Zheng
- Beijing Key Laboratory of Pediatric Hematology Oncology, National Key Discipline of Pediatrics, Ministry of Education, MOE Key Laboratory of Major Diseases in Children, Hematology Oncology Center, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing, 100045 China
| | - Wei Ding
- 3Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, Beijing, 100069 China.,4Beijing Key Laboratory for Tumor Invasion and Metastasis Research, Cancer Institute of Capital Medical University, Beijing, 100069 China
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7
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Song Y, Niu J, Yue Z, Gao R, Zhang C, Ding W. Increased chemo-sensitivity by knockdown coilin expression involved acceleration of premature cellular senescence in HeLa cells. Biochem Biophys Res Commun 2017; 489:123-129. [PMID: 28536075 DOI: 10.1016/j.bbrc.2017.05.108] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Accepted: 05/19/2017] [Indexed: 12/22/2022]
Abstract
Coilin is a marker protein of the Cajal body (CB). Cajal bodies, functional nuclear structure, play important roles for the maturation of telomerase mRNAs. However, whether CB participates in the process of cell senescence is unknown. Cisplatin is a frequently used drug for the chemotherapy for various cancers, which was recently reported to be able to induce premature senescence of tumor cells. In this study, we found that when HeLa cells were treated with 2 μg/ml cisplatin for 4 days, stagnant cell growth, especially in cells stained positive of SA-β-gal, was accompanied with significant changes in CB morphologies. The removal of cisplatin allowed the recovery of normal CB appearance, but was not able to restore cells from senescent states. Knocking down coilin expression by siRNA attenuated the growth and reduced the viability of treated cells, and the decreased rate of CB formation correlated with increased staining of SA-β-gal. Interestingly, when coilin knocked-down cells exposed to cisplatin, the drug sensitivity as shown by the reduction of cell viability was significantly increased compared to the control siRNA transfection groups. Overexpression of coilin phosphomutants increased SA-β-gal fluorescence following treatments with cisplatin as compared to the wild type coilin transfection. Our results indicated that coilin was an important functional player that involved in cisplatin-induced premature cell senescence. It suggested that the modulation of coilin expression could be considered as a potential anti-tumor strategy to increase the sensitivity of chemotherapy through which drug-induced cell senescence was accelerated.
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Affiliation(s)
- Yaoyao Song
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, PR China
| | - Jing Niu
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, PR China; Beijing Key Laboratory for Tumor Invasion and Metastasis Research, Cancer Institute of Capital Medical University, PR China
| | - Zhixia Yue
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, PR China; Hematology Oncology Center at Beijing Children's Hospital in Affiliation of Capital Medical University, PR China
| | - Ruiqi Gao
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, PR China
| | - Chenguang Zhang
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, PR China; Beijing Key Laboratory for Tumor Invasion and Metastasis Research, Cancer Institute of Capital Medical University, PR China
| | - Wei Ding
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Capital Medical University, PR China; Beijing Key Laboratory for Tumor Invasion and Metastasis Research, Cancer Institute of Capital Medical University, PR China; Beijing Institute of Brain Disorders, PR China.
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8
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Trinkle-Mulcahy L, Sleeman JE. The Cajal body and the nucleolus: "In a relationship" or "It's complicated"? RNA Biol 2016; 14:739-751. [PMID: 27661468 DOI: 10.1080/15476286.2016.1236169] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
From their initial identification as 'nucleolar accessory bodies' more than a century ago, the relationship between Cajal bodies and nucleoli has been a subject of interest and controversy. In this review, we seek to place recent developments in the understanding of the physical and functional relationships between the 2 structures in the context of historical observations. Biophysical models of nuclear body formation, the molecular nature of CB/nucleolus interactions and the increasing list of joint roles for CBs and nucleoli, predominantly in assembling ribonucleoprotein (RNP) complexes, are discussed.
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Affiliation(s)
- Laura Trinkle-Mulcahy
- a Department of Cellular and Molecular Medicine , Ottawa Institute of Systems Biology, University of Ottawa , Ottawa , ON , Canada
| | - Judith E Sleeman
- b BSRC Complex, School of Biology, University of St Andrews , UK
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9
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Fayzullina S, Martin LJ. DNA Damage Response and DNA Repair in Skeletal Myocytes From a Mouse Model of Spinal Muscular Atrophy. J Neuropathol Exp Neurol 2016; 75:889-902. [PMID: 27452406 DOI: 10.1093/jnen/nlw064] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We studied DNA damage response (DDR) and DNA repair capacities of skeletal muscle cells from a mouse model of infantile spinal muscular atrophy (SMA) caused by loss-of-function mutation of survival of motor neuron (Smn). Primary myocyte cultures derived from skeletal muscle satellite cells of neonatal control and mutant SMN mice had similar myotube length, myonuclei, satellite cell marker Pax7 and differentiated myotube marker myosin, and acetylcholine receptor clustering. DNA damage was induced in differentiated skeletal myotubes by γ-irradiation, etoposide, and methyl methanesulfonate (MMS). Unexposed control and SMA myotubes had stable genome integrity. After γ-irradiation and etoposide, myotubes repaired most DNA damage equally. Control and mutant myotubes exposed to MMS exhibited equivalent DNA damage without repair. Control and SMA myotube nuclei contained DDR proteins phospho-p53 and phospho-H2AX foci that, with DNA damage, dispersed and then re-formed similarly after recovery. We conclude that mouse primary satellite cell-derived myotubes effectively respond to and repair DNA strand-breaks, while DNA alkylation repair is underrepresented. Morphological differentiation, genome stability, genome sensor, and DNA strand-break repair potential are preserved in mouse SMA myocytes; thus, reduced SMN does not interfere with myocyte differentiation, genome integrity, and DNA repair, and faulty DNA repair is unlikely pathogenic in SMA.
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Affiliation(s)
- Saniya Fayzullina
- From the Department of Pathology, Division of Neuropathology, and the Pathobiology Graduate Training Program, Johns Hopkins School of Medicine, Baltimore, Maryland, USA (SF, LJM)
| | - Lee J Martin
- From the Department of Pathology, Division of Neuropathology, and the Pathobiology Graduate Training Program, Johns Hopkins School of Medicine, Baltimore, Maryland, USA (SF, LJM)
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10
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Abstract
Initially identified as a marker of coiled bodies (now Cajal bodies or CBs), the protein coilin was discovered a quarter of century ago. Coilin is now known to scaffold the CB, but its structure and function are poorly understood. Nearly devoid of predicted structural motifs, coilin has numerous reported molecular interactions that must underlie its role in the formation and function of CBs. In this review, we summarize what we have learned in the past 25 years about coilin's structure, post-transcriptional modifications, and interactions with RNA and proteins. We show that genes with homology to human coilin are found in primitive metazoans and comment on differences among model organisms. Coilin's function in Cajal body formation and RNP metabolism will be discussed in the light of these developments.
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Affiliation(s)
- Martin Machyna
- a Department of Molecular Biophysics & Biochemistry ; Yale University ; New Haven , CT USA
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11
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Henriksson S, Farnebo M. On the road with WRAP53β: guardian of Cajal bodies and genome integrity. Front Genet 2015; 6:91. [PMID: 25852739 PMCID: PMC4371746 DOI: 10.3389/fgene.2015.00091] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Accepted: 02/19/2015] [Indexed: 12/16/2022] Open
Abstract
The WRAP53 gene encodes both an antisense transcript (WRAP53α) that stabilizes the tumor suppressor p53 and a protein (WRAP53β) involved in maintenance of Cajal bodies, telomere elongation and DNA repair. WRAP53β is one of many proteins containing WD40 domains, known to mediate a variety of cellular processes. These proteins lack enzymatic activity, acting instead as platforms for the assembly of large complexes of proteins and RNAs thus facilitating their interactions. WRAP53β mediates site-specific interactions between Cajal body factors and DNA repair proteins. Moreover, dysfunction of this protein has been linked to premature aging, cancer and neurodegeneration. Here we summarize the current state of knowledge concerning the multifaceted roles of WRAP53β in intracellular trafficking, formation of the Cajal body, DNA repair and maintenance of genomic integrity and discuss potential crosstalk between these processes.
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Affiliation(s)
- Sofia Henriksson
- Science for Life Laboratory, Division of Translational Medicine and Chemical Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet Stockholm, Sweden
| | - Marianne Farnebo
- Department of Oncology-Pathology, Cancer Centrum Karolinska, Karolinska Institutet Stockholm, Sweden
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12
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Henriksson S, Rassoolzadeh H, Hedström E, Coucoravas C, Julner A, Goldstein M, Imreh G, Zhivotovsky B, Kastan MB, Helleday T, Farnebo M. The scaffold protein WRAP53β orchestrates the ubiquitin response critical for DNA double-strand break repair. Genes Dev 2015; 28:2726-38. [PMID: 25512560 PMCID: PMC4265676 DOI: 10.1101/gad.246546.114] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The WD40 domain-containing protein WRAP53β controls trafficking of splicing factors and telomerase to Cajal bodies. Here, Henriksson et al. demonstrate that WRAP53β rapidly localizes to double-strand breaks (DSBs) in an ATM-, H2AX-, and MDC1-dependent manner. WRAP53β targets the E3 ligase RNF8 to DNA lesions by facilitating the interaction between RNF8 and its upstream partner, MDC1, in response to DNA damage. Loss of WRAP53β impairs DSB repair by both homologous recombination and nonhomologous end-joining, causes accumulation of spontaneous DNA breaks, and delays recovery from radiation-induced cell cycle arrest. The WD40 domain-containing protein WRAP53β (WD40 encoding RNA antisense to p53; also referred to as WDR79/TCAB1) controls trafficking of splicing factors and the telomerase enzyme to Cajal bodies, and its functional loss has been linked to carcinogenesis, premature aging, and neurodegeneration. Here, we identify WRAP53β as an essential regulator of DNA double-strand break (DSB) repair. WRAP53β rapidly localizes to DSBs in an ATM-, H2AX-, and MDC1-dependent manner. We show that WRAP53β targets the E3 ligase RNF8 to DNA lesions by facilitating the interaction between RNF8 and its upstream partner, MDC1, in response to DNA damage. Simultaneous binding of MDC1 and RNF8 to the highly conserved WD40 scaffold domain of WRAP53β facilitates their interaction and accumulation of RNF8 at DSBs. In this manner, WRAP53β controls proper ubiquitylation at DNA damage sites and the downstream assembly of 53BP1, BRCA1, and RAD51. Furthermore, we reveal that knockdown of WRAP53β impairs DSB repair by both homologous recombination (HR) and nonhomologous end-joining (NHEJ), causes accumulation of spontaneous DNA breaks, and delays recovery from radiation-induced cell cycle arrest. Our findings establish WRAP53β as a novel regulator of DSB repair by providing a scaffold for DNA repair factors.
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Affiliation(s)
- Sofia Henriksson
- Department of Oncology-Pathology, Cancer Centrum Karolinska (CCK), Karolinska Institutet, Stockholm 171 76, Sweden
| | - Hanif Rassoolzadeh
- Department of Oncology-Pathology, Cancer Centrum Karolinska (CCK), Karolinska Institutet, Stockholm 171 76, Sweden
| | - Elisabeth Hedström
- Department of Oncology-Pathology, Cancer Centrum Karolinska (CCK), Karolinska Institutet, Stockholm 171 76, Sweden
| | - Christos Coucoravas
- Department of Oncology-Pathology, Cancer Centrum Karolinska (CCK), Karolinska Institutet, Stockholm 171 76, Sweden
| | - Alexander Julner
- Department of Oncology-Pathology, Cancer Centrum Karolinska (CCK), Karolinska Institutet, Stockholm 171 76, Sweden
| | - Michael Goldstein
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, North Carolina 27710, USA
| | - Gabriela Imreh
- Institute for Environmental Medicine, Karolinska Institutet, Stockholm 171 77, Sweden
| | - Boris Zhivotovsky
- Institute for Environmental Medicine, Karolinska Institutet, Stockholm 171 77, Sweden
| | - Michael B Kastan
- Department of Pharmacology and Cancer Biology, Duke University School of Medicine, Durham, North Carolina 27710, USA
| | - Thomas Helleday
- Science for Life Laboratory, Division of Translational Medicine and Chemical Biology, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm 171 65, Sweden
| | - Marianne Farnebo
- Department of Oncology-Pathology, Cancer Centrum Karolinska (CCK), Karolinska Institutet, Stockholm 171 76, Sweden;
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13
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Abstract
This review summarizes the current understanding of the role of nuclear bodies in regulating gene expression. The compartmentalization of cellular processes, such as ribosome biogenesis, RNA processing, cellular response to stress, transcription, modification and assembly of spliceosomal snRNPs, histone gene synthesis and nuclear RNA retention, has significant implications for gene regulation. These functional nuclear domains include the nucleolus, nuclear speckle, nuclear stress body, transcription factory, Cajal body, Gemini of Cajal body, histone locus body and paraspeckle. We herein review the roles of nuclear bodies in regulating gene expression and their relation to human health and disease.
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Affiliation(s)
| | - Cornelius F. Boerkoel
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-604-875-2157; Fax: +1-604-875-2376
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14
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Enwerem II, Velma V, Broome HJ, Kuna M, Begum RA, Hebert MD. Coilin association with Box C/D scaRNA suggests a direct role for the Cajal body marker protein in scaRNP biogenesis. Biol Open 2014; 3:240-9. [PMID: 24659245 PMCID: PMC3988793 DOI: 10.1242/bio.20147443] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Spliceosomal small nuclear ribonucleoproteins (snRNPs) are enriched in the Cajal body (CB). Guide RNAs, known as small Cajal body-specific RNAs (scaRNAs), direct modification of the small nuclear RNA (snRNA) component of the snRNP. The protein WRAP53 binds a sequence motif (the CAB box) found in many scaRNAs and the RNA component of telomerase (hTR) and targets these RNAs to the CB. We have previously reported that coilin, the CB marker protein, associates with certain non-coding RNAs. For a more comprehensive examination of the RNAs associated with coilin, we have sequenced the RNA isolated from coilin immunocomplexes. A striking preferential association of coilin with the box C/D scaRNAs 2 and 9, which lack a CAB box, was observed. This association varied by treatment condition and WRAP53 knockdown. In contrast, reduction of WRAP53 did not alter the level of coilin association with hTR. Additional studies showed that coilin degrades/processes scaRNA 2 and 9, associates with active telomerase and can influence telomerase activity. These findings suggest that coilin plays a novel role in the biogenesis of box C/D scaRNPs and telomerase.
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Affiliation(s)
- Isioma I Enwerem
- Department of Biochemistry, The University of Mississippi Medical Center, Jackson, MS 39216-4505, USA
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15
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Fayzullina S, Martin LJ. Skeletal muscle DNA damage precedes spinal motor neuron DNA damage in a mouse model of Spinal Muscular Atrophy (SMA). PLoS One 2014; 9:e93329. [PMID: 24667816 PMCID: PMC3965546 DOI: 10.1371/journal.pone.0093329] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2013] [Accepted: 03/03/2014] [Indexed: 12/27/2022] Open
Abstract
Spinal Muscular Atrophy (SMA) is a hereditary childhood disease that causes paralysis by progressive degeneration of skeletal muscles and spinal motor neurons. SMA is associated with reduced levels of full-length Survival of Motor Neuron (SMN) protein, due to mutations in the Survival of Motor Neuron 1 gene. The mechanisms by which lack of SMN causes SMA pathology are not known, making it very difficult to develop effective therapies. We investigated whether DNA damage is a perinatal pathological event in SMA, and whether DNA damage and cell death first occur in skeletal muscle or spinal cord of SMA mice. We used a mouse model of severe SMA to ascertain the extent of cell death and DNA damage throughout the body of prenatal and newborn mice. SMA mice at birth (postnatal day 0) exhibited internucleosomal fragmentation in genomic DNA from hindlimb skeletal muscle, but not in genomic DNA from spinal cord. SMA mice at postnatal day 5, compared with littermate controls, exhibited increased apoptotic cell death profiles in skeletal muscle, by hematoxylin and eosin, terminal deoxynucleotidyl transferase dUTP nick end labeling, and electron microscopy. SMA mice had no increased cell death, no loss of choline acetyl transferase (ChAT)-positive motor neurons, and no overt pathology in the ventral horn of the spinal cord. At embryonic days 13 and 15.5, SMA mice did not exhibit statistically significant increases in cell death profiles in spinal cord or skeletal muscle. Motor neuron numbers in the ventral horn, as identified by ChAT immunoreactivity, were comparable in SMA mice and control littermates at embryonic day 15.5 and postnatal day 5. These observations demonstrate that in SMA, disease in skeletal muscle emerges before pathology in spinal cord, including loss of motor neurons. Overall, this work identifies DNA damage and cell death in skeletal muscle as therapeutic targets for SMA.
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Affiliation(s)
- Saniya Fayzullina
- Division of Neuropathology, Department of Pathology, and the Pathobiology Graduate Program, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
- * E-mail:
| | - Lee J. Martin
- Division of Neuropathology, Department of Pathology, and the Pathobiology Graduate Program, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
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16
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Shaw J, Love AJ, Makarova SS, Kalinina NO, Harrison BD, Taliansky ME. Coilin, the signature protein of Cajal bodies, differentially modulates the interactions of plants with viruses in widely different taxa. Nucleus 2014; 5:85-94. [PMID: 24637832 PMCID: PMC4028359 DOI: 10.4161/nucl.28315] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2013] [Revised: 02/18/2014] [Accepted: 02/21/2014] [Indexed: 12/28/2022] Open
Abstract
Cajal bodies (CBs) are distinct nuclear bodies physically and functionally associated with the nucleolus. In addition to their traditional function in coordinating maturation of certain nuclear RNAs, CBs participate in cell cycle regulation, development, and regulation of stress responses. A key "signature" component of CBs is coilin, the scaffolding protein essential for CB formation and function. Using an RNA silencing (loss-of-function) approach, we describe here new phenomena whereby coilin also affects, directly or indirectly, a variety of interactions between host plants and viruses that have RNA or DNA genomes. Moreover, the effects of coilin on these interactions are manifested differently: coilin contributes to plant defense against tobacco rattle virus (tobravirus), tomato black ring virus (nepovirus), barley stripe mosaic virus (hordeivirus), and tomato golden mosaic virus (begomovirus). In contrast, with potato virus Y (potyvirus) and turnip vein clearing virus (tobamovirus), coilin serves to increase virus pathogenicity. These findings show that interactions with coilin (or CBs) may involve diverse mechanisms with different viruses and that these mechanisms act at different phases of virus infection. Thus, coilin (CBs) has novel, unexpected natural functions that may be recruited or subverted by plant viruses for their own needs or, in contrast, are involved in plant defense mechanisms that suppress host susceptibility to the viruses.
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Affiliation(s)
- Jane Shaw
- Cell and Molecular Sciences; The James Hutton Institute; Dundee, UK
| | - Andrew J Love
- Cell and Molecular Sciences; The James Hutton Institute; Dundee, UK
| | - Svetlana S Makarova
- AN Belozersky Institute of Physico-Chemical Biology; Moscow State University; Moscow, Russia
| | - Natalia O Kalinina
- AN Belozersky Institute of Physico-Chemical Biology; Moscow State University; Moscow, Russia
| | - Bryan D Harrison
- Cell and Molecular Sciences; The James Hutton Institute; Dundee, UK
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17
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Förthmann B, van Bergeijk J, Lee YW, Lübben V, Schill Y, Brinkmann H, Ratzka A, Stachowiak MK, Hebert M, Grothe C, Claus P. Regulation of neuronal differentiation by proteins associated with nuclear bodies. PLoS One 2013; 8:e82871. [PMID: 24358231 PMCID: PMC3866168 DOI: 10.1371/journal.pone.0082871] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2013] [Accepted: 11/06/2013] [Indexed: 12/17/2022] Open
Abstract
Nuclear bodies are large sub-nuclear structures composed of RNA and protein molecules. The Survival of Motor Neuron (SMN) protein localizes to Cajal bodies (CBs) and nuclear gems. Diminished cellular concentration of SMN is associated with the neurodegenerative disease Spinal Muscular Atrophy (SMA). How nuclear body architecture and its structural components influence neuronal differentiation remains elusive. In this study, we analyzed the effects of SMN and two of its interaction partners in cellular models of neuronal differentiation. The nuclear 23 kDa isoform of Fibroblast Growth Factor - 2 (FGF-2(23)) is one of these interacting proteins - and was previously observed to influence nuclear bodies by destabilizing nuclear gems and mobilizing SMN from Cajal bodies (CBs). Here we demonstrate that FGF-2(23) blocks SMN-promoted neurite outgrowth, and also show that SMN disrupts FGF-2(23)-dependent transcription. Our results indicate that FGF-2(23) and SMN form an inactive complex that interferes with neuronal differentiation by mutually antagonizing nuclear functions. Coilin is another nuclear SMN binding partner and a marker protein for Cajal bodies (CBs). In addition, coilin is essential for CB function in maturation of small nuclear ribonucleoprotein particles (snRNPs). The role of coilin outside of Cajal bodies and its putative impacts in tissue differentiation are poorly defined. The present study shows that protein levels of nucleoplasmic coilin outside of CBs decrease during neuronal differentiation. Overexpression of coilin has an inhibitory effect on neurite outgrowth. Furthermore, we find that nucleoplasmic coilin inhibits neurite outgrowth independent of SMN binding revealing a new function for coilin in neuronal differentiation.
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Affiliation(s)
- Benjamin Förthmann
- Institute of Neuroanatomy, Hannover Medical School, Hannover, Germany
- Center for Systems Neuroscience, University of Veterinary Medicine Hannover, Hannover, Germany
| | | | - Yu-Wei Lee
- Department of Pathology and Anatomical Sciences, State University of New York, Buffalo, New York, United States of America
| | - Verena Lübben
- Institute of Neuroanatomy, Hannover Medical School, Hannover, Germany
| | - Yvonne Schill
- Institute of Neuroanatomy, Hannover Medical School, Hannover, Germany
| | - Hella Brinkmann
- Institute of Neuroanatomy, Hannover Medical School, Hannover, Germany
| | - Andreas Ratzka
- Institute of Neuroanatomy, Hannover Medical School, Hannover, Germany
| | - Michal K. Stachowiak
- Department of Pathology and Anatomical Sciences, State University of New York, Buffalo, New York, United States of America
| | - Michael Hebert
- Department of Biochemistry, The University of Mississippi Medical Center, Jackson, Mississippi, United States of America
| | - Claudia Grothe
- Institute of Neuroanatomy, Hannover Medical School, Hannover, Germany
- Center for Systems Neuroscience, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Peter Claus
- Institute of Neuroanatomy, Hannover Medical School, Hannover, Germany
- Center for Systems Neuroscience, University of Veterinary Medicine Hannover, Hannover, Germany
- * E-mail:
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18
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Plant coilin: structural characteristics and RNA-binding properties. PLoS One 2013; 8:e53571. [PMID: 23320094 PMCID: PMC3539977 DOI: 10.1371/journal.pone.0053571] [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] [Received: 08/29/2012] [Accepted: 12/03/2012] [Indexed: 01/26/2023] Open
Abstract
Cajal bodies (CBs) are dynamic subnuclear compartments involved in the biogenesis of ribonucleoproteins. Coilin is a major structural scaffolding protein necessary for CB formation, composition and activity. The predicted secondary structure of Arabidopsis thaliana coilin (Atcoilin) suggests that the protein is composed of three main domains. Analysis of the physical properties of deletion mutants indicates that Atcoilin might consist of an N-terminal globular domain, a central highly disordered domain and a C-terminal domain containing a presumable Tudor-like structure adjacent to a disordered C terminus. Despite the low homology in amino acid sequences, a similar type of domain organization is likely shared by human and animal coilin proteins and coilin-like proteins of various plant species. Atcoilin is able to bind RNA effectively and in a non-specific manner. This activity is provided by three RNA-binding sites: two sets of basic amino acids in the N-terminal domain and one set in the central domain. Interaction with RNA induces the multimerization of the Atcoilin molecule, a consequence of the structural alterations in the N-terminal domain. The interaction with RNA and subsequent multimerization may facilitate coilin’s function as a scaffolding protein. A model of the N-terminal domain is also proposed.
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19
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Broome HJ, Hebert MD. Coilin displays differential affinity for specific RNAs in vivo and is linked to telomerase RNA biogenesis. J Mol Biol 2012; 425:713-24. [PMID: 23274112 DOI: 10.1016/j.jmb.2012.12.014] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2012] [Revised: 11/29/2012] [Accepted: 12/18/2012] [Indexed: 12/19/2022]
Abstract
Coilin is widely known as the protein marker of the Cajal body, a subnuclear domain important to the biogenesis of small nuclear ribonucleoproteins and telomerase, complexes that are crucial to pre-messenger RNA splicing and telomere maintenance, respectively. Extensive studies have characterized the interaction between coilin and the various other protein components of CBs and related subnuclear domains; however, only a few have examined interactions between coilin and nucleic acid. We have recently published that coilin is tightly associated with nucleic acid, displays RNase activity in vitro, and is redistributed to the ribosomal RNA (rRNA)-rich nucleoli in cells treated with the DNA-damaging agents cisplatin and etoposide. Here, we report a specific in vivo association between coilin and rRNA, U small nuclear RNA (snRNA), and human telomerase RNA, which is altered upon treatment with DNA-damaging agents. Using chromatin immunoprecipitation, we provide evidence of coilin interaction with specific regions of U snRNA gene loci. We have also utilized bacterially expressed coilin fragments in order to map the region(s) important for RNA binding and RNase activity in vitro. Additionally, we provide evidence of coilin involvement in the processing of human telomerase RNA both in vitro and in vivo.
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Affiliation(s)
- Hanna J Broome
- Department of Biochemistry, The University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39216-4505, USA.
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20
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Velma V, Carrero ZI, Allen CB, Hebert MD. Coilin levels modulate cell cycle progression and γH2AX levels in etoposide treated U2OS cells. FEBS Lett 2012; 586:3404-9. [PMID: 22986342 DOI: 10.1016/j.febslet.2012.07.054] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Revised: 07/05/2012] [Accepted: 07/17/2012] [Indexed: 11/28/2022]
Abstract
Coilin is considered the Cajal body (CB) marker protein. In this report, we investigated the role of coilin in the DNA damage response and found that coilin reduction correlated with significantly increased levels of soluble γH2AX in etoposide treated U2OS cells. Additionally, coilin levels influenced the proliferation rate and cell cycle distribution of cells exposed to etoposide. Moreover, coilin overexpression inhibited nucleolar localization of endogenous coilin in etoposide treated U2OS cells. Collectively, these data provide additional evidence for coilin and CBs in the DNA damage response.
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Affiliation(s)
- Venkatramreddy Velma
- Department of Biochemistry, The University of Mississippi Medical Center, Jackson, MS 39216-4505, USA
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21
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In vitro RNase and nucleic acid binding activities implicate coilin in U snRNA processing. PLoS One 2012; 7:e36300. [PMID: 22558428 PMCID: PMC3338655 DOI: 10.1371/journal.pone.0036300] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Accepted: 04/04/2012] [Indexed: 11/21/2022] Open
Abstract
Coilin is known as the marker protein for Cajal bodies (CBs), subnuclear domains important for the biogenesis of small nuclear ribonucleoproteins (snRNPs) which function in pre-mRNA splicing. CBs associate non-randomly with U1 and U2 gene loci, which produce the small nuclear RNA (snRNA) component of the respective snRNP. Despite recognition as the CB marker protein, coilin is primarily nucleoplasmic, and the function of this fraction is not fully characterized. Here we show that coilin binds double stranded DNA and has RNase activity in vitro. U1 and U2 snRNAs undergo a processing event of the primary transcript prior to incorporation in the snRNP. We find that coilin displays RNase activity within the CU region of the U2 snRNA primary transcript in vitro, and that coilin knockdown results in accumulation of the 3′ pre-processed U1 and U2 snRNA. These findings present new characteristics of coilin in vitro, and suggest additional functions of the protein in vivo.
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22
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Carrero ZI, Velma V, Douglas HE, Hebert MD. Coilin phosphomutants disrupt Cajal body formation, reduce cell proliferation and produce a distinct coilin degradation product. PLoS One 2011; 6:e25743. [PMID: 21991343 PMCID: PMC3185009 DOI: 10.1371/journal.pone.0025743] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2011] [Accepted: 09/09/2011] [Indexed: 12/17/2022] Open
Abstract
Coilin is a nuclear phosphoprotein that accumulates in Cajal bodies (CBs). CBs participate in ribonucleoprotein and telomerase biogenesis, and are often found in cells with high transcriptional demands such as neuronal and cancer cells, but can also be observed less frequently in other cell types such as fibroblasts. Many proteins enriched within the CB are phosphorylated, but it is not clear what role this modification has on the activity of these proteins in the CB. Coilin is considered to be the CB marker protein and is essential for proper CB formation and composition in mammalian cells. In order to characterize the role of coilin phosphorylation on CB formation, we evaluated various coilin phosphomutants using transient expression. Additionally, we generated inducible coilin phosphomutant cell lines that, when used in combination with endogenous coilin knockdown, allow for the expression of the phosphomutants at physiological levels. Transient expression of all coilin phosphomutants except the phosphonull mutant (OFF) significantly reduces proliferation. Interestingly, a stable cell line induced to express the coilin S489D phosphomutant displays nucleolar accumulation of the mutant and generates a N-terminal degradation product; neither of which is observed upon transient expression. A N-terminal degradation product and nucleolar localization are also observed in a stable cell line induced to express a coilin phosphonull mutant (OFF). The nucleolar localization of the S489D and OFF coilin mutants observed in the stable cell lines is decreased when endogenous coilin is reduced. Furthermore, all the phosphomutant cells lines show a significant reduction in CB formation when compared to wild-type after endogenous coilin knockdown. Cell proliferation studies on these lines reveal that only wild-type coilin and the OFF mutant are sufficient to rescue the reduction in proliferation associated with endogenous coilin depletion. These results emphasize the role of coilin phosphorylation in the formation and activity of CBs.
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Affiliation(s)
- Zunamys I. Carrero
- Department of Biochemistry, The University of Mississippi Medical Center, Jackson, Mississippi, United States of America
| | - Venkatramreddy Velma
- Department of Biochemistry, The University of Mississippi Medical Center, Jackson, Mississippi, United States of America
| | - Heather E. Douglas
- Department of Biochemistry, The University of Mississippi Medical Center, Jackson, Mississippi, United States of America
| | - Michael D. Hebert
- Department of Biochemistry, The University of Mississippi Medical Center, Jackson, Mississippi, United States of America
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23
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Gilder AS, Do PM, Carrero ZI, Cosman AM, Broome HJ, Velma V, Martinez LA, Hebert MD. Coilin participates in the suppression of RNA polymerase I in response to cisplatin-induced DNA damage. Mol Biol Cell 2011; 22:1070-9. [PMID: 21289084 PMCID: PMC3069010 DOI: 10.1091/mbc.e10-08-0731] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
This study's findings identify a novel and unexpected function for coilin, independentof its role in snRNP biogenesis, establishing a new link between the DNA damage response and the inhibition of rRNA synthesis. Coilin is a nuclear phosphoprotein that concentrates within Cajal bodies (CBs) and impacts small nuclear ribonucleoprotein (snRNP) biogenesis. Cisplatin and γ-irradiation, which cause distinct types of DNA damage, both trigger the nucleolar accumulation of coilin, and this temporally coincides with the repression of RNA polymerase I (Pol I) activity. Knockdown of endogenous coilin partially overrides the Pol I transcriptional arrest caused by cisplatin, while both ectopically expressed and exogenous coilin accumulate in the nucleolus and suppress rRNA synthesis. In support of this mechanism, we demonstrate that both cisplatin and γ-irradiation induce the colocalization of coilin with RPA-194 (the largest subunit of Pol I), and we further show that coilin can specifically interact with RPA-194 and the key regulator of Pol I activity, upstream binding factor (UBF). Using chromatin immunoprecipitation analysis, we provide evidence that coilin modulates the association of Pol I with ribosomal DNA. Collectively, our data suggest that coilin acts to repress Pol I activity in response to cisplatin-induced DNA damage. Our findings identify a novel and unexpected function for coilin, independent of its role in snRNP biogenesis, establishing a new link between the DNA damage response and the inhibition of rRNA synthesis.
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Affiliation(s)
- Andrew S Gilder
- Department of Biochemistry, University of Mississippi Medical Center, Jackson, MS 39216, USA
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