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Machyna M, Kehr S, Straube K, Kappei D, Buchholz F, Butter F, Ule J, Hertel J, Stadler PF, Neugebauer KM. The coilin interactome identifies hundreds of small noncoding RNAs that traffic through Cajal bodies. Mol Cell 2014; 56:389-399. [PMID: 25514182 DOI: 10.1016/j.molcel.2014.10.004] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2014] [Revised: 08/25/2014] [Accepted: 10/02/2014] [Indexed: 12/21/2022]
Abstract
Coilin protein scaffolds Cajal bodies (CBs)-subnuclear compartments enriched in small nuclear RNAs (snRNAs)-and promotes efficient spliceosomal snRNP assembly. The molecular function of coilin, which is intrinsically disordered with no defined motifs, is poorly understood. We use UV crosslinking and immunoprecipitation (iCLIP) to determine whether mammalian coilin binds RNA in vivo and to identify targets. Robust detection of snRNA transcripts correlated with coilin ChIP-seq peaks on snRNA genes, indicating that coilin binding to nascent snRNAs is a site-specific CB nucleator. Surprisingly, several hundred small nucleolar RNAs (snoRNAs) were identified as coilin interactors, including numerous unannotated mouse and human snoRNAs. We show that all classes of snoRNAs concentrate in CBs. Moreover, snoRNAs lacking specific CB retention signals traffic through CBs en route to nucleoli, consistent with the role of CBs in small RNP assembly. Thus, coilin couples snRNA and snoRNA biogenesis, making CBs the cellular hub of small ncRNA metabolism.
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Affiliation(s)
- Martin Machyna
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany; Department of Molecular Biophysics & Biochemistry, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
| | - Stephanie Kehr
- Bioinformatics Group, Department of Computer Science and Interdisciplinary Center for Bioinformatics, University of Leipzig, Haertelstrasse 16-18, 04107 Leipzig, Germany
| | - Korinna Straube
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany; Department of Molecular Biophysics & Biochemistry, Yale University, 333 Cedar Street, New Haven, CT 06520, USA
| | - Dennis Kappei
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Frank Buchholz
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany
| | - Falk Butter
- Institute of Molecular Biology (IMB), Ackermannweg 4, 55128 Mainz, Germany
| | - Jernej Ule
- Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London WC1N 3BG, UK
| | - Jana Hertel
- Bioinformatics Group, Department of Computer Science and Interdisciplinary Center for Bioinformatics, University of Leipzig, Haertelstrasse 16-18, 04107 Leipzig, Germany
| | - Peter F Stadler
- Bioinformatics Group, Department of Computer Science and Interdisciplinary Center for Bioinformatics, University of Leipzig, Haertelstrasse 16-18, 04107 Leipzig, Germany
| | - Karla M Neugebauer
- Max Planck Institute of Molecular Cell Biology and Genetics, Pfotenhauerstrasse 108, 01307 Dresden, Germany; Department of Molecular Biophysics & Biochemistry, Yale University, 333 Cedar Street, New Haven, CT 06520, USA.
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Machyna M, Heyn P, Neugebauer KM. Cajal bodies: where form meets function. WILEY INTERDISCIPLINARY REVIEWS-RNA 2012; 4:17-34. [PMID: 23042601 DOI: 10.1002/wrna.1139] [Citation(s) in RCA: 140] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The cell nucleus contains dozens of subcompartments that separate biochemical processes into confined spaces. Cajal bodies (CBs) were discovered more than 100 years ago, but only extensive research in the past decades revealed the surprising complexity of molecular and cellular functions taking place in these structures. Many protein and RNA species are modified and assembled within CBs, which have emerged as a meeting place and factory for ribonucleoprotein (RNP) particles involved in splicing, ribosome biogenesis and telomere maintenance. Recently, a distinct structure near histone gene clusters--the Histone locus body (HLB)--was discovered. Involved in histone mRNA 3'-end formation, HLBs can share several components with CBs. Whether the appearance of distinct HLBs is simply a matter of altered affinity between these structures or of an alternate mode of CB assembly is unknown. However, both structures share basic assembly properties, in which transcription plays a decisive role in initiation. After this seeding event, additional components associate in random order. This appears to be a widespread mechanism for body assembly. CB assembly encompasses an additional layer of complexity, whereby a set of pre-existing substructures can be integrated into mature CBs. We propose this as a multi-seeding model of CB assembly.
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Affiliation(s)
- Martin Machyna
- Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
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Pombo A. Advances in imaging the interphase nucleus using thin cryosections. Histochem Cell Biol 2007; 128:97-104. [PMID: 17636315 DOI: 10.1007/s00418-007-0310-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/21/2007] [Indexed: 01/01/2023]
Abstract
The mammalian genome is partitioned amongst various chromosomes and encodes for approximately 30,000 protein-coding genes. Gene expression occurs after exit from mitosis, when chromosomes partially decondense within the cell nucleus to allow the enzymatic activities that work on chromatin to access each gene in a regulated fashion. Differential patterns of gene expression evolve during cell differentiation to give rise to the over 200 cell types in higher eukaryotes. The architectural organisation of the genome inside the interphase cell nucleus, and associated enzymatic activities, reveals dynamic and functional compartmentalization of the genome. In this review, I highlight the advantages of Tokuyasu cryosectioning on the investigation of nuclear structure and function.
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Affiliation(s)
- Ana Pombo
- Nuclear Organisation Group, MRC Clinical Sciences Centre, Imperial College School of Medicine, Hammersmith Hospital Campus, Du Cane Road, London, W12 0NN, UK.
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Stanek D, Neugebauer KM. The Cajal body: a meeting place for spliceosomal snRNPs in the nuclear maze. Chromosoma 2006; 115:343-54. [PMID: 16575476 DOI: 10.1007/s00412-006-0056-6] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2005] [Revised: 01/27/2006] [Accepted: 01/29/2006] [Indexed: 10/24/2022]
Abstract
Spliceosomal small nuclear ribonucleoprotein particles (snRNPs) are essential pre-mRNA splicing factors that consist of small nuclear RNAs (snRNAs) complexed with specific sets of proteins. A considerable body of evidence has established that snRNP assembly is accomplished after snRNA synthesis in the nucleus through a series of steps involving cytoplasmic and nuclear phases. Recent work indicates that snRNPs transiently localize to the Cajal body (CB), a nonmembrane-bound inclusion present in the nuclei of most cells, for the final steps in snRNP maturation, including snRNA base modification, U4/U6 snRNA annealing, and snRNA-protein assembly. Here, we review these findings that suggest a crucial role for CBs in the spliceosome cycle in which production of new snRNPs--and perhaps regenerated snRNPs after splicing--is promoted by the concentration of substrates in this previously mysterious subnuclear organelle. These insights allow us to speculate on the role of nuclear bodies in regulating the dynamics of RNP assembly to maintain a functional pool of factors available for key steps in gene expression.
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Affiliation(s)
- David Stanek
- Department of Cellular Biology and Pathology, First Medical Faculty, Institute of Physiology, Charles University, Academy of Sciences of the Czech Republic, Albertov 4, Prague 2, 128 00, Czech Republic.
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Boulon S, Basyuk E, Blanchard JM, Bertrand E, Verheggen C. Intra-nuclear RNA trafficking: insights from live cell imaging. Biochimie 2002; 84:805-13. [PMID: 12457567 DOI: 10.1016/s0300-9084(02)01438-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Despite recent advances, the mechanisms of RNA movements and targeting within the nucleus are still mysterious. While diffusion appears to play a crucial role in nuclear dynamics and RNA transport, some data argue for a model in which diffusion is controlled, at least in part, by the organization of the nucleus in well-defined compartments. Much of the recent progress is based on imaging technologies, and this review will first present them in some detail. We will then summarize studies that analyzed nuclear movements of both polyadenylated RNA and box C/D snoRNP. Indeed, this latter model has already brought a number of interesting results. We will finally present some of our original results on box C/D snoRNA transport.
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Affiliation(s)
- Séverine Boulon
- IGMM-CNRS UMR 5535, IFR24, 1919, route de Mende, 34293 Montpellier cedex 5, France
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Sleeman JE, Ajuh P, Lamond AI. snRNP protein expression enhances the formation of Cajal bodies containing p80-coilin and SMN. J Cell Sci 2001; 114:4407-19. [PMID: 11792806 DOI: 10.1242/jcs.114.24.4407] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Splicing snRNPs (small nuclear ribonucleoproteins) are essential sub-units of the spliceosome. Here we report the establishment of stable cell lines expressing fluorescently tagged SmB, a core snRNP protein. Analysis of these stable cell lines has allowed us to characterize the nuclear pathway that leads to snRNP accumulation in nuclear speckles and has identified a limiting nucleolar step in the pathway that can be saturated by overexpression of Sm proteins. After nuclear import, newly assembled snRNPs accumulate first in a subset of Cajal bodies that contain both p80-coilin and the survival of motor neurons protein (SMN) and not in bodies that contain p80-coilin but lack SMN. Treatment of cells with leptomycin B (LMB) inhibits both the accumulation of snRNPs in nuclear bodies and their subsequent accumulation in speckles. The formation of Cajal bodies is enhanced by Sm protein expression and the assembly of new snRNPs. Formation of heterokaryons between HeLa cell lines expressing Sm proteins and primary cells that usually lack Cajal bodies results in the detection of Cajal bodies in primary cell nuclei. Transient over-expression of exogenous SmB alone is sufficient to induce correspondingly transient Cajal body formation in primary cells. These data indicate that the level of snRNP protein expression and snRNP assembly, rather than the expression levels of p80-coilin or SMN, may be a key trigger for Cajal body formation.
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Affiliation(s)
- J E Sleeman
- School of Life Sciences, University of Dundee, MSI/WTB Complex, Dow Street, Dundee, DD1 5EH, UK
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He W, Ikeda S, Bronson RT, Yan G, Nishina PM, North MA, Naggert JK. GFP-tagged expression and immunohistochemical studies to determine the subcellular localization of the tubby gene family members. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2000; 81:109-17. [PMID: 11000483 DOI: 10.1016/s0169-328x(00)00164-9] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The tubby gene family consists of four members, TUB, TULP1, TULP2 and TULP3, with unknown function. However, a splice junction mutation within the mouse tub gene leads to retinal and cochlear degeneration, as well as maturity onset obesity and insulin resistance. Mutations within human TULP1 have also been shown to co-segregate in several cases of autosomal recessive retinitis pigmentosa (RP) and TULP1 deficiency in mice leads to retinal degeneration. The primary amino acid sequences of the tubby family members do not predict a likely biochemical function. As a first step in defining their function, we present a detailed characterization of the cellular and subcellular localization of the human (TUB) and mouse (tub) homologous gene products. We report the isolation of TUB splice variants which have different subcellular localizations (nuclear versus cytoplasmic) and which define a nuclear localization signal. In addition, using green fluorescent protein (GFP) tags, we observe a nuclear localization for TULP1, similar to TUB splicing forms TUB 561 and TUB 506. Finally, we report tubby expression in mouse brain by in situ hybridization and by immunohistochemistry with polyclonal antibodies. Protein was found in both the hypothalamic satiety centers and in a variety of other CNS structures including the cortex, cerebellum, olfactory bulb and hippocampus. Both nuclear and cytoplasmic signals were detected with a series of independently generated polyclonal antibodies, consistent with the presence of multiple alternatively spliced isoforms within the CNS.
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Affiliation(s)
- W He
- AXYS Pharmaceuticals, La Jolla, CA 92037, USA
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Abstract
Structures visible within the eukaryotic nucleus have fascinated generations of biologists. Recent data show that these structures form in response to gene expression and are highly dynamic in living cells. RNA processing and assembly require many factors but the nucleus apparently lacks any active transport system to deliver these to the RNAs. Instead, processing factors move by diffusion but are concentrated by transient association with functionally related components. At sites of high activity this gives rise to visible structures, with components in dynamic equilibrium with the surrounding nucleoplasm. Processing factors are recruited from this pool by cooperative binding to RNA substrates.
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Affiliation(s)
- J D Lewis
- Wellcome Trust Centre for Cell Biology, ICMB, King's Buildings, The University of Edinburgh, Edinburgh EH9 3JR, Scotland, UK
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