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Histone gene expression and histone mRNA 3' end structure in Caenorhabditis elegans. BMC Mol Biol 2007; 8:51. [PMID: 17570845 PMCID: PMC1924863 DOI: 10.1186/1471-2199-8-51] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2007] [Accepted: 06/14/2007] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Histone protein synthesis is essential for cell proliferation and required for the packaging of DNA into chromatin. In animals, histone proteins are provided by the expression of multicopy replication-dependent histone genes. Histone mRNAs that are processed by a histone-specific mechanism to end after a highly conserved RNA hairpin element, and lack a poly(A) tail. In vertebrates and Drosophila, their expression is dependent on HBP/SLBP that binds to the RNA hairpin element. We showed previously that these cis and trans acting regulators of histone gene expression are conserved in C. elegans. Here we report the results of an investigation of the histone mRNA 3' end structure and of histone gene expression during C. elegans development. RESULTS Sequence analysis of replication-dependent histone genes revealed the presence of several highly conserved sequence elements in the 3' untranslated region of histone pre-mRNAs, including an RNA hairpin element and a polyadenylation signal. To determine whether in C. elegans histone mRNA 3' end formation occurs at this polyadenylation signal and results in polyadenylated histone mRNA, we investigated the mRNA 3' end structure of histone mRNA. Using poly(A) selection, RNAse protection and sequencing of histone mRNA ends, we determined that a majority of C. elegans histone mRNAs lack a poly(A) tail and end three to six nucleotides after the hairpin structure, after an A or a U, and have a 3' OH group. RNAi knock down of CDL-1, the C. elegans HBP/SLBP, does not significantly affect histone mRNA levels but severely depletes histone protein levels. Histone gene expression varies during development and is reduced in L3 animals compared to L1 animals and adults. In adults, histone gene expression is restricted to the germ line, where cell division occurs. CONCLUSION Our findings indicate that the expression of C. elegans histone genes is subject to control mechanisms similar to the ones in other animals: the structure of C. elegans histone mRNA 3' ends is compatible with histone-specific mRNA 3' end processing; CDL-1 functions in post-transcriptional control of histone gene expression; and C. elegans histone mRNA levels are elevated at periods of active cell division, indicating that histone gene expression is linked to DNA replication.
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Borchers CH, Thapar R, Petrotchenko EV, Torres MP, Speir JP, Easterling M, Dominski Z, Marzluff WF. Combined top-down and bottom-up proteomics identifies a phosphorylation site in stem-loop-binding proteins that contributes to high-affinity RNA binding. Proc Natl Acad Sci U S A 2006; 103:3094-9. [PMID: 16492733 PMCID: PMC1413926 DOI: 10.1073/pnas.0511289103] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2005] [Indexed: 11/18/2022] Open
Abstract
The stem-loop-binding protein (SLBP) is involved in multiple aspects of histone mRNA metabolism. To characterize the modification status and sites of SLBP, we combined mass spectrometric bottom-up (analysis of peptides) and top-down (analysis of intact proteins) proteomic approaches. Drosophilia SLBP is heavily phosphorylated, containing up to seven phosphoryl groups. Accurate M(r) determination by Fourier transform ion cyclotron resonance (FTICR)-MS and FTICR-MS top-down experiments using a variety of dissociation techniques show there is removal of the initiator methionine and acetylation of the N terminus in the baculovirus-expressed protein, and that T230 is stoichiometrically phosphorylated. T230 is highly conserved; we have determined that this site is also completely phosphorylated in baculovirus-expressed mammalian SLBP and extensively phosphorylated in both Drosophila and mammalian cultured cells. Removal of the phosphoryl group from T230 by either dephosphorylation or mutation results in a 7-fold reduction in the affinity of SLBP for the stem-loop RNA.
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Affiliation(s)
| | - Roopa Thapar
- *Department of Biochemistry and Biophysics and
- Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill, NC 27599; and
| | | | | | | | | | - Zbigniew Dominski
- *Department of Biochemistry and Biophysics and
- Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill, NC 27599; and
| | - William F. Marzluff
- *Department of Biochemistry and Biophysics and
- Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill, NC 27599; and
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3
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Gorgoni B, Andrews S, Schaller A, Schümperli D, Gray NK, Müller B. The stem-loop binding protein stimulates histone translation at an early step in the initiation pathway. RNA (NEW YORK, N.Y.) 2005; 11:1030-42. [PMID: 15987814 PMCID: PMC1370788 DOI: 10.1261/rna.7281305] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
Metazoan replication-dependent histone mRNAs do not have a poly(A) tail but end instead in a conserved stem-loop structure. Efficient translation of these mRNAs is dependent on the stem-loop binding protein (SLBP). Here we explore the mechanism by which SLBP stimulates translation in vertebrate cells, using the tethered function assay and analyzing protein-protein interactions. We show for the first time that translational stimulation by SLBP increases during oocyte maturation and that SLBP stimulates translation at the level of initiation. We demonstrate that SLBP can interact directly with subunit h of eIF3 and with Paip1; however, neither of these interactions is sufficient to mediate its effects on translation. We find that Xenopus SLBP1 functions primarily at an early stage in the cap-dependent initiation pathway, targeting small ribosomal subunit recruitment. Analysis of IRES-driven translation in Xenopus oocytes suggests that SLBP activity requires eIF4E. We propose a model in which a novel factor contacts eIF4E bound to the 5' cap and SLBP bound to the 3' end simultaneously, mediating formation of an alternative end-to-end complex.
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Affiliation(s)
- Barbara Gorgoni
- MRC Human Genetics Unit, Western General Hospital, Crewe Road, Edinburgh EH4 2XU, Scotland, United Kingdom
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4
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Pillai RS, Grimmler M, Meister G, Will CL, Lührmann R, Fischer U, Schümperli D. Unique Sm core structure of U7 snRNPs: assembly by a specialized SMN complex and the role of a new component, Lsm11, in histone RNA processing. Genes Dev 2003; 17:2321-33. [PMID: 12975319 PMCID: PMC196468 DOI: 10.1101/gad.274403] [Citation(s) in RCA: 178] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
A set of seven Sm proteins assemble on the Sm-binding site of spliceosomal U snRNAs to form the ring-shaped Sm core. The U7 snRNP involved in histone RNA 3' processing contains a structurally similar but biochemically unique Sm core in which two of these proteins, Sm D1 and D2, are replaced by Lsm10 and by another as yet unknown component. Here we characterize this factor, termed Lsm11, as a novel Sm-like protein with apparently two distinct functions. In vitro studies suggest that its long N-terminal part mediates an important step in histone mRNA 3'-end cleavage, most likely by recruiting a zinc finger protein previously identified as a processing factor. In contrast, the C-terminal part, which comprises two Sm motifs interrupted by an unusually long spacer, is sufficient to assemble with U7, but not U1, snRNA. Assembly of this U7-specific Sm core depends on the noncanonical Sm-binding site of U7 snRNA. Moreover, it is facilitated by a specialized SMN complex that contains Lsm10 and Lsm11 but lacks Sm D1/D2. Thus, the U7-specific Lsm11 protein not only specifies the assembly of the U7 Sm core but also fulfills an important role in U7 snRNP-mediated histone mRNA processing.
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Affiliation(s)
- Ramesh S Pillai
- Institute of Cell Biology, University of Bern, 3012 Bern, Switzerland
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5
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Adamson TE, Price DH. Cotranscriptional processing of Drosophila histone mRNAs. Mol Cell Biol 2003; 23:4046-55. [PMID: 12773550 PMCID: PMC156150 DOI: 10.1128/mcb.23.12.4046-4055.2003] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2002] [Revised: 02/06/2003] [Accepted: 03/21/2003] [Indexed: 11/20/2022] Open
Abstract
The 3' ends of metazoan histone mRNAs are generated by specialized processing machinery that cleaves downstream of a conserved stem-loop structure. To examine how this reaction might be influenced by transcription, we used a Drosophila melanogaster in vitro system that supports both processes. In this system the complete synthesis of histone mRNA, including transcription initiation and elongation, followed by 3' end formation, occurred at a physiologically significant rate. Processing of free transcripts was efficient and occurred with a t(1/2) of less than 1 min. Divalent cations were not required, but nucleoside triphosphates (NTPs) stimulated the rate of cleavage slightly. Isolated elongation complexes encountered a strong arrest site downstream of the mature histone H4 3' end. In the presence of NTPs, transcripts in these arrested complexes were processed at a rate similar to that of free RNA. Removal of NTPs dramatically reduced this rate, potentially due to concealment of the U7 snRNP binding element. The arrest site was found to be a conserved feature located 32 to 35 nucleotides downstream of the processing site on the H4, H2b, and H3 genes. The significance of the newly discovered arrest sites to our understanding of the coupling between transcription and RNA processing on the one hand and histone gene expression on the other is discussed.
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Affiliation(s)
- Todd E Adamson
- Department of Biochemistry, University of Iowa, Iowa City, Iowa 52242, USA
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Jády BE, Darzacq X, Tucker KE, Matera AG, Bertrand E, Kiss T. Modification of Sm small nuclear RNAs occurs in the nucleoplasmic Cajal body following import from the cytoplasm. EMBO J 2003; 22:1878-88. [PMID: 12682020 PMCID: PMC154478 DOI: 10.1093/emboj/cdg187] [Citation(s) in RCA: 192] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Biogenesis of functional spliceosomal small nuclear RNAs (snRNAs) includes the post-transcriptional covalent modification of numerous internal nucleotides. We have recently demonstrated that synthesis of 2'-O-methylated nucleotides and pseudouridines in the RNA polymerase II-synthesized Sm snRNAs is directed by sequence-specific guide RNAs. Here, we provide evidence supporting the notion that modification of Sm snRNAs occurs in nucleoplasmic Cajal bodies (CBs), where modification guide RNAs accumulate. We show that short fragments of Sm snRNAs are correctly and efficiently modified when targeted to CBs, but not when these same fragments are targeted to the nucleolus. We also demonstrate that internal modification of the U2 snRNA occurs exclusively after nuclear import of the newly assembled Sm snRNP from the cytoplasm. Finally, we show that p80 coilin, the CB marker protein, is not required for snRNA modification. In coilin knockout cells, Sm snRNAs and their modification guide RNAs colocalize in residual CBs, which do not stockpile fibrillarin and fail to recruit the U3 small nucleolar RNA.
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Affiliation(s)
- Beáta E Jády
- Laboratoire de Biologie Moléculaire Eucaryote du CNRS, Université Paul Sabatier, 118 route de Narbonne, 31062 Toulouse Cedex, France
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7
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Allard P, Champigny MJ, Skoggard S, Erkmann JA, Whitfield ML, Marzluff WF, Clarke HJ. Stem-loop binding protein accumulates during oocyte maturation and is not cell-cycle-regulated in the early mouse embryo. J Cell Sci 2002; 115:4577-86. [PMID: 12415002 PMCID: PMC5115915 DOI: 10.1242/jcs.00132] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The stem-loop binding protein (SLBP) binds to the 3' end of histone mRNA and participates in 3'-processing of the newly synthesized transcripts, which protects them from degradation, and probably also promotes their translation. In proliferating cells, translation of SLBP mRNA begins at G1/S and the protein is degraded following DNA replication. These post-transcriptional mechanisms closely couple SLBP expression to S-phase of the cell cycle, and play a key role in restricting synthesis of replication-dependent histones to S-phase. In contrast to somatic cells, replication-dependent histone mRNAs accumulate and are translated independently of DNA replication in oocytes and early embryos. We report here that SLBP expression and activity also differ in mouse oocytes and early embryos compared with somatic cells. SLBP is present in oocytes that are arrested at prophase of G2/M, where it is concentrated in the nucleus. Upon entry into M-phase of meiotic maturation, SLBP begins to accumulate rapidly, reaching a very high level in mature oocytes arrested at metaphase II. Following fertilization, SLBP remains abundant in the nucleus and the cytoplasm throughout the first cell cycle, including both G1 and G2 phases. It declines during the second and third cell cycles, reaching a relatively low level by the late 4-cell stage. SLBP can bind the histone mRNA-stem-loop at all stages of the cell cycle in oocytes and early embryos, and it is the only stem-loop binding activity detectable in these cells. We also report that SLBP becomes phosphorylated rapidly following entry into M-phase of meiotic maturation through a mechanism that is sensitive to roscovitine, an inhibitor of cyclin-dependent kinases. SLBP is rapidly dephosphorylated following fertilization or parthenogenetic activation, and becomes newly phosphorylated at M-phase of mitosis. Phosphorylation does not affect its stem-loop binding activity. These results establish that, in contrast to Xenopus, mouse oocytes and embryos contain a single SLBP. Expression of SLBP is uncoupled from S-phase in oocytes and early embryos, which indicates that the mechanisms that impose cell-cycle-regulated expression of SLBP in somatic cells do not operate in oocytes or during the first embryonic cell cycle. This distinctive pattern of SLBP expression may be required for accumulation of histone proteins required for sperm chromatin remodelling and assembly of newly synthesized embryonic DNA into chromatin.
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Affiliation(s)
- Patrick Allard
- Departments of Obstetrics and Gynecology and Biology, McGill University, Montreal, Quebec, Canada H3A 1A1
| | - Marc J. Champigny
- Departments of Obstetrics and Gynecology and Biology, McGill University, Montreal, Quebec, Canada H3A 1A1
| | - Sarah Skoggard
- Departments of Obstetrics and Gynecology and Biology, McGill University, Montreal, Quebec, Canada H3A 1A1
| | - Judith A. Erkmann
- Department of Biochemistry and Biophysics and Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Michael L. Whitfield
- Department of Biochemistry and Biophysics and Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - William F. Marzluff
- Department of Biochemistry and Biophysics and Program in Molecular Biology and Biotechnology, University of North Carolina, Chapel Hill, NC 27599, USA
| | - Hugh J. Clarke
- Departments of Obstetrics and Gynecology and Biology, McGill University, Montreal, Quebec, Canada H3A 1A1
- Department of Medicine, McGill University, Montreal, Quebec, Canada H3A 1A1
- Author for correspondence ()
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8
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Pettitt J, Crombie C, Schümperli D, Müller B. TheCaenorhabditis eleganshistone hairpin-binding protein is required for core histone gene expression and is essential for embryonic and postembryonic cell division. J Cell Sci 2002; 115:857-66. [PMID: 11865041 DOI: 10.1242/jcs.115.4.857] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
As in all metazoans, the replication-dependent histone genes of Caenorhabditis elegans lack introns and contain a short hairpin structure in the 3′ untranslated region. This hairpin structure is a key element for post-transcriptional regulation of histone gene expression and determines mRNA 3′ end formation, nuclear export, translation and mRNA decay. All these steps contribute to the S-phase-specific expression of the replication-dependent histone genes. The hairpin structure is the binding site for histone hairpin-binding protein that is required for hairpin-dependent regulation. Here, we demonstrate that the C. elegans histone hairpin-binding protein gene is transcribed in dividing cells during embryogenesis and postembryonic development. Depletion of histone hairpin-binding protein (HBP) function in early embryos using RNA-mediated interference leads to an embryonic-lethal phenotype brought about by defects in chromosome condensation. A similar phenotype was obtained by depleting histones H3 and H4 in early embryos, indicating that the defects in hairpin-binding protein-depleted embryos are caused by reduced histone biosynthesis. We have confirmed this by showing that HBP depletion reduces histone gene expression. Depletion of HBP during postembryonic development also results in defects in cell division during late larval development. In addition, we have observed defects in the specification of vulval cell fate in animals depleted for histone H3 and H4, which indicates that histone proteins are required for cell fate regulation during vulval development.
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Affiliation(s)
- Jonathan Pettitt
- Department of Molecular and Cell Biology, Institute of Medical Sciences, University of Aberdeen, Aberdeen AB25 2ZD, Scotland, UK
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9
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Kodama Y, Rothman JH, Sugimoto A, Yamamoto M. The stem-loop binding protein CDL-1 is required for chromosome condensation, progression of cell death and morphogenesis inCaenorhabditis elegans. Development 2002; 129:187-96. [PMID: 11782412 DOI: 10.1242/dev.129.1.187] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Histones play important roles not only in the structural changes of chromatin but also in regulating gene expression. Expression of histones is partly regulated post-transcriptionally by the stem-loop binding protein (SLBP)/hairpin binding protein (HBP). We report the developmental function of CDL-1, the C. elegans homologue of SLBP/HBP. In the C. elegans cdl-1 mutants, cell corpses resulting from programmed cell death appear later and persist much longer than those in the wild type. They also exhibit distinct morphological defects in body elongation and movement of the pharyngeal cells toward the buccal opening. The CDL-1 protein binds to the stem-loop structures in the 3′-UTR of C. elegans core histone mRNAs, and the mutant forms of this protein show reduced binding activities. A decrease in the amount of core histone proteins phenocopied the cdl-1 mutant embryos, suggesting that CDL-1 contributes to the proper expression of core histone proteins. We propose that loss-of-function of cdl-1 causes aberrant chromatin structure, which affects the cell cycle and cell death, as well as transcription of genes essential for morphogenesis.
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Affiliation(s)
- Yuki Kodama
- Department of Biophysics and Biochemistry, Graduate School of Science, University of Tokyo, Bunkyo, 113-0032, Japan
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10
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Meister G, Bühler D, Pillai R, Lottspeich F, Fischer U. A multiprotein complex mediates the ATP-dependent assembly of spliceosomal U snRNPs. Nat Cell Biol 2001; 3:945-9. [PMID: 11715014 DOI: 10.1038/ncb1101-945] [Citation(s) in RCA: 238] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The spliceosomal snRNPs U1, U2, U4 and U5 contain a common RNP structure termed the Sm core that is formed by the binding of Sm proteins onto the U snRNA. Although isolated Sm proteins assemble spontaneously onto U snRNAs in vitro, there is increasing evidence that SMN and its interactor Gemin2 are involved in this process in vivo. Here, we describe a cell-free assay system for the assembly of U snRNPs that closely reproduces in vivo conditions. Using this system, we show that assembly of U1 snRNP depends on ATP. Immunodepletion of SMN-Gemin2 from the extract abolished assembly even though the extract contained high levels of Sm proteins. An affinity-purified macromolecular SMN complex consisting of 16 components including all Sm proteins restored assembly in the immunodepleted extract. These data provide the first direct evidence that a complex containing SMN and Gemin2 mediates the active assembly of spliceosomal U snRNPs.
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Affiliation(s)
- G Meister
- Max-Planck Institute of Biochemistry, Am Klopferspitz 18a, D-82152 Martinsried, Germany
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11
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Tucker KE, Berciano MT, Jacobs EY, LePage DF, Shpargel KB, Rossire JJ, Chan EK, Lafarga M, Conlon RA, Matera AG. Residual Cajal bodies in coilin knockout mice fail to recruit Sm snRNPs and SMN, the spinal muscular atrophy gene product. J Cell Biol 2001; 154:293-307. [PMID: 11470819 PMCID: PMC2150753 DOI: 10.1083/jcb.200104083] [Citation(s) in RCA: 187] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Cajal bodies (CBs) are nuclear suborganelles involved in the biogenesis of small nuclear ribonucleoproteins (snRNPs). In addition to snRNPs, they are highly enriched in basal transcription and cell cycle factors, the nucleolar proteins fibrillarin (Fb) and Nopp140 (Nopp), the survival motor neuron (SMN) protein complex, and the CB marker protein, p80 coilin. We report the generation of knockout mice lacking the COOH-terminal 487 amino acids of coilin. Northern and Western blot analyses demonstrate that we have successfully removed the full-length coilin protein from the knockout animals. Some homozygous mutant animals are viable, but their numbers are reduced significantly when crossed to inbred backgrounds. Analysis of tissues and cell lines from mutant animals reveals the presence of extranucleolar foci that contain Fb and Nopp but not other typical nucleolar markers. These so-called "residual" CBs neither condense Sm proteins nor recruit members of the SMN protein complex. Transient expression of wild-type mouse coilin in knockout cells results in formation of CBs and restores these missing epitopes. Our data demonstrate that full-length coilin is essential for proper formation and/or maintenance of CBs and that recruitment of snRNP and SMN complex proteins to these nuclear subdomains requires sequences within the coilin COOH terminus.
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Affiliation(s)
- K E Tucker
- Department of Genetics, and Program in Cell Biology, Case Western Reserve University and University Hospitals of Cleveland, Cleveland, OH 44106, USA
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