51
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Haurie V, Ménard L, Nicou A, Touriol C, Metzler P, Fernandez J, Taras D, Lestienne P, Balabaud C, Bioulac-Sage P, Prats H, Zucman-Rossi J, Rosenbaum J. Adenosine triphosphatase pontin is overexpressed in hepatocellular carcinoma and coregulated with reptin through a new posttranslational mechanism. Hepatology 2009; 50:1871-83. [PMID: 19877184 PMCID: PMC2927003 DOI: 10.1002/hep.23215] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
UNLABELLED Reptin and Pontin are related ATPases associated with stoichiometric amounts in several complexes involved in chromatin remodeling, transcriptional regulation, and telomerase activity. We found that Reptin was up-regulated in hepatocellular carcinoma (HCC) and that down-regulation of Reptin led to growth arrest. We show here that Pontin messenger RNA (mRNA) is also up-regulated in human HCC 3.9-fold as compared to nontumor liver (P = 0.0004). Pontin expression was a strong independent factor of poor prognosis in a multivariate analysis. As for Reptin, depletion of Pontin in HuH7 cells with small interfering RNAs (siRNAs) led to growth arrest. Remarkably, Pontin depletion led to down-regulation of Reptin as shown with western blot, and vice versa. Whereas siRNAs induced a decrease of their cognate mRNA targets, they did not affect the transcripts of the partner protein. Translation of Pontin or Reptin was not altered when the partner protein was silenced. However, pulse-chase experiments demonstrated that newly synthesized Pontin or Reptin stability was reduced in Reptin- or Pontin-depleted cells, respectively. This phenomenon was reversed upon inhibition of proteasome or ubiquitin-activating enzyme (E1). In addition, proteasome inhibition could partly restore Pontin steady-state levels in Reptin-depleted cells, as shown by western blot. This restoration was not observed when cells were also treated with cycloheximide, thus confirming that proteasomal degradation in this setting was restricted to newly synthesized Pontin. CONCLUSION Reptin and Pontin protein levels are strictly controlled by a posttranslational mechanism involving proteasomal degradation of newly synthesized proteins. These data demonstrate a tight regulatory and reciprocal interaction between Reptin and Pontin, which may in turn lead to the maintenance of their 1:1 stoichiometry.
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Affiliation(s)
- Valérie Haurie
- Fibrose hépatique et cancer du foie
INSERM : U889Université Victor Segalen - Bordeaux IIIFR66146 rue léo saignat, 33076 Bordeaux Cedex,FR
| | - Ludovic Ménard
- Fibrose hépatique et cancer du foie
INSERM : U889Université Victor Segalen - Bordeaux IIIFR66146 rue léo saignat, 33076 Bordeaux Cedex,FR
| | - Alexandra Nicou
- Fibrose hépatique et cancer du foie
INSERM : U889Université Victor Segalen - Bordeaux IIIFR66146 rue léo saignat, 33076 Bordeaux Cedex,FR
| | - Christian Touriol
- I2MR, Institut de médecine moléculaire de Rangueil
INSERM : U858IFR31IFR150Université Paul Sabatier - Toulouse IIIInstitut Louis Bugnard 1, avenue Jean Poulhes BP 84225 31432 TOULOUSE CEDEX 4,FR
| | - Philippe Metzler
- Fibrose hépatique et cancer du foie
INSERM : U889Université Victor Segalen - Bordeaux IIIFR66146 rue léo saignat, 33076 Bordeaux Cedex,FR
| | - Jérémy Fernandez
- Fibrose hépatique et cancer du foie
INSERM : U889Université Victor Segalen - Bordeaux IIIFR66146 rue léo saignat, 33076 Bordeaux Cedex,FR
| | - Danièle Taras
- Fibrose hépatique et cancer du foie
INSERM : U889Université Victor Segalen - Bordeaux IIIFR66146 rue léo saignat, 33076 Bordeaux Cedex,FR
| | - Patrick Lestienne
- Fibrose hépatique et cancer du foie
INSERM : U889Université Victor Segalen - Bordeaux IIIFR66146 rue léo saignat, 33076 Bordeaux Cedex,FR
| | - Charles Balabaud
- Fibrose hépatique et cancer du foie
INSERM : U889Université Victor Segalen - Bordeaux IIIFR66146 rue léo saignat, 33076 Bordeaux Cedex,FR,Service d'hépato-gastroentérologie
CHU BordeauxFR
| | - Paulette Bioulac-Sage
- Fibrose hépatique et cancer du foie
INSERM : U889Université Victor Segalen - Bordeaux IIIFR66146 rue léo saignat, 33076 Bordeaux Cedex,FR,Laboratoire d'anatomie pathologique
CHU BordeauxGroupe hospitalier PellegrinFR
| | - Hervé Prats
- I2MR, Institut de médecine moléculaire de Rangueil
INSERM : U858IFR31IFR150Université Paul Sabatier - Toulouse IIIInstitut Louis Bugnard 1, avenue Jean Poulhes BP 84225 31432 TOULOUSE CEDEX 4,FR
| | - Jessica Zucman-Rossi
- Genomique Fonctionnelle des Tumeurs Solides
INSERM : U674Université Paris-Diderot - Paris VIIIFR105Hopital Saint-Louis - IFR 105 PARIS VII 27, Rue Juliette Dodu 75010 PARIS,FR
| | - Jean Rosenbaum
- Fibrose hépatique et cancer du foie
INSERM : U889Université Victor Segalen - Bordeaux IIIFR66146 rue léo saignat, 33076 Bordeaux Cedex,FR,* Correspondence should be adressed to: Jean Rosenbaum
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Leung KN, Vallero RO, DuBose AJ, Resnick JL, LaSalle JM. Imprinting regulates mammalian snoRNA-encoding chromatin decondensation and neuronal nucleolar size. Hum Mol Genet 2009; 18:4227-38. [PMID: 19656775 PMCID: PMC2766290 DOI: 10.1093/hmg/ddp373] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Imprinting, non-coding RNA and chromatin organization are modes of epigenetic regulation that modulate gene expression and are necessary for mammalian neurodevelopment. The only two known mammalian clusters of genes encoding small nucleolar RNAs (snoRNAs), SNRPN through UBE3A(15q11–q13/7qC) and GTL2(14q32.2/12qF1), are neuronally expressed, localized to imprinted loci and involved in at least five neurodevelopmental disorders. Deficiency of the paternal 15q11–q13 snoRNA HBII-85 locus is necessary to cause the neurodevelopmental disorder Prader–Willi syndrome (PWS). Here we show epigenetically regulated chromatin decondensation at snoRNA clusters in human and mouse brain. An 8-fold allele-specific decondensation of snoRNA chromatin was developmentally regulated specifically in maturing neurons, correlating with HBII-85 nucleolar accumulation and increased nucleolar size. Reciprocal mouse models revealed a genetic and epigenetic requirement of the 35 kb imprinting center (IC) at the Snrpn–Ube3a locus for transcriptionally regulated chromatin decondensation. PWS human brain and IC deletion mouse Purkinje neurons showed significantly decreased nucleolar size, demonstrating the essential role of the 15q11–q13 HBII-85 locus in neuronal nucleolar maturation. These results are relevant to understanding the molecular pathogenesis of multiple human neurodevelopmental disorders, including PWS and some causes of autism.
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Affiliation(s)
- Karen N Leung
- Microbiology and Immunology and Rowe Program in Human Genetics, UC Davis School of Medicine, Davis, CA 95616, USA
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53
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Evidence that the AAA+ proteins TIP48 and TIP49 bridge interactions between 15.5K and the related NOP56 and NOP58 proteins during box C/D snoRNP biogenesis. Mol Cell Biol 2009; 29:4971-81. [PMID: 19620283 DOI: 10.1128/mcb.00752-09] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The box C/D small nucleolar RNPs (snoRNPs) are essential for the processing and modification of rRNA. TIP48 and TIP49 are two related AAA(+) proteins that are essential for the formation of box C/D snoRNPs. These proteins are key components of the pre-snoRNP complexes, but their exact role in box C/D snoRNP biogenesis is largely uncharacterized. Here we report that TIP48 and TIP49 interact with one another in vitro, and only the TIP48/TIP49 complex, but not the individual proteins, possesses significant ATPase activity. Loss of TIP48 and TIP49 results in a change in pre-snoRNA levels and a loss of U3 snoRNA signal in the Cajal body. We show that TIP48 and TIP49 make multiple interactions with core snoRNP proteins and biogenesis factors and that these interactions are often regulated by the presence of ATP. Furthermore, we demonstrate that TIP48 and TIP49 efficiently bridge interactions between the core box C/D proteins NOP56 or NOP58 and 15.5K. Our data imply that the snoRNP assembly factor NUFIP can regulate the interactions between TIP48 and TIP49 and the core box C/D proteins. We suggest that snoRNP assembly involves an intricate series of interactions that are mediated/regulated by bridging factors and chaperones.
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54
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Jha S, Dutta A. RVB1/RVB2: running rings around molecular biology. Mol Cell 2009; 34:521-33. [PMID: 19524533 DOI: 10.1016/j.molcel.2009.05.016] [Citation(s) in RCA: 176] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2009] [Revised: 04/25/2009] [Accepted: 05/20/2009] [Indexed: 12/31/2022]
Abstract
RVB1/RVB2 (also known as Pontin/Reptin, TIP49/TIP48, RuvbL1/RuvbL2, ECP54/ECP51, INO80H/INO80J, TIH1/TIH2, and TIP49A/TIP49B) are two highly conserved members of the AAA+ family that are present in different protein and nucleoprotein complexes. Recent studies implicate the RVB-containing complexes in many cellular processes such as transcription, DNA damage response, snoRNP assembly, cellular transformation, and cancer metastasis. In this review, we discuss recent advances in our understanding of RVB-containing complexes and their role in these pathways.
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Affiliation(s)
- Sudhakar Jha
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Virginia, Jordan 1240, 1340 Jefferson Park Avenue, Charlottesville, VA 22908, USA
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55
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Abstract
In pro- and eukaryotic cells, RuvB-like protein 2 (RBL2) resolves Holliday junction recombination intermediates. Here, we identified RBL2 as a suppressor of influenza A virus replication. Human RBL2 appears to interfere with the oligomerization of the viral nucleoprotein, a critical step in the assembly of viral replication complexes.
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56
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de Planell-Saguer M, Schroeder DG, Rodicio MC, Cox GA, Mourelatos Z. Biochemical and genetic evidence for a role of IGHMBP2 in the translational machinery. Hum Mol Genet 2009; 18:2115-26. [PMID: 19299493 DOI: 10.1093/hmg/ddp134] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The human motor neuron degenerative disease spinal muscular atrophy with respiratory distress type 1 (SMARD1) is caused by loss of function mutations of immunoglobulin mu-binding protein 2 (IGHMBP2), a protein of unknown function that contains DNA/RNA helicase and nucleic acid-binding domains. Reduced IGHMBP2 protein levels in neuromuscular degeneration (nmd) mice, the mouse model of SMARD1, lead to motor neuron degeneration. We report the biochemical characterization of IGHMBP2 and the isolation of a modifier locus that rescues the phenotype and motor neuron degeneration of nmd mice. We find that a 166 kb BAC transgene derived from CAST/EiJ mice and containing tRNA genes and activator of basal transcription 1 (Abt1), a protein-coding gene that is required for ribosome biogenesis, contains the genetic modifier responsible for motor neuron rescue. Our biochemical investigations show that IGHMBP2 associates physically with tRNAs and in particular with tRNA(Tyr), which are present in the modifier and with the ABT1 protein. We find that transcription factor IIIC-220 kDa (TFIIIC220), an essential factor required for tRNA transcription, and the helicases Reptin and Pontin, which function in transcription and in ribosome biogenesis, are also part of IGHMBP2-containing complexes. Our findings strongly suggest that IGHMBP2 is a component of the translational machinery and that these components can be manipulated genetically to suppress motor neuron degeneration.
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Affiliation(s)
- Mariàngels de Planell-Saguer
- Department of Pathology and Laboratory Medicine, Division of Neuropathology, University of Pennsylvania School of Medicine, Philadelphia, PA 19104-6100, USA
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57
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Chromatin Central: towards the comparative proteome by accurate mapping of the yeast proteomic environment. Genome Biol 2008; 9:R167. [PMID: 19040720 PMCID: PMC2614481 DOI: 10.1186/gb-2008-9-11-r167] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2008] [Revised: 10/21/2008] [Accepted: 11/28/2008] [Indexed: 01/01/2023] Open
Abstract
High resolution mapping of the proteomic environment and proteomic hyperlinks in fission and budding yeast reveals that divergent hyperlinks are due to gene duplications. Background Understanding the design logic of living systems requires the understanding and comparison of proteomes. Proteomes define the commonalities between organisms more precisely than genomic sequences. Because uncertainties remain regarding the accuracy of proteomic data, several issues need to be resolved before comparative proteomics can be fruitful. Results The Saccharomyces cerevisiae proteome presents the highest quality proteomic data available. To evaluate the accuracy of these data, we intensively mapped a proteomic environment, termed 'Chromatin Central', which encompasses eight protein complexes, including the major histone acetyltransferases and deacetylases, interconnected by twelve proteomic hyperlinks. Using sequential tagging and a new method to eliminate background, we confirmed existing data but also uncovered new subunits and three new complexes, including ASTRA, which we suggest is a widely conserved aspect of telomeric maintenance, and two new variations of Rpd3 histone deacetylase complexes. We also examined the same environment in fission yeast and found a very similar architecture based on a scaffold of orthologues comprising about two-thirds of all proteins involved, whereas the remaining one-third is less constrained. Notably, most of the divergent hyperlinks were found to be due to gene duplications, hence providing a mechanism for the fixation of gene duplications in evolution. Conclusions We define several prerequisites for comparative proteomics and apply them to examine a proteomic environment in unprecedented detail. We suggest that high resolution mapping of proteomic environments will deliver the highest quality data for comparative proteomics.
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58
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Sheaffer KL, Updike DL, Mango SE. The Target of Rapamycin pathway antagonizes pha-4/FoxA to control development and aging. Curr Biol 2008; 18:1355-64. [PMID: 18804378 DOI: 10.1016/j.cub.2008.07.097] [Citation(s) in RCA: 125] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2008] [Revised: 07/28/2008] [Accepted: 07/29/2008] [Indexed: 12/22/2022]
Abstract
BACKGROUND FoxA factors are critical regulators of embryonic development and postembryonic life, but little is know about the upstream pathways that modulate their activity. C. elegans pha-4 encodes a FoxA transcription factor that is required to establish the foregut in embryos and to control growth and longevity after birth. We previously identified the AAA+ ATPase homolog ruvb-1 as a potent suppressor of pha-4 mutations. RESULTS Here we show that ruvb-1 is a component of the Target of Rapamycin (TOR) pathway in C. elegans (CeTOR). Both ruvb-1 and let-363/TOR control nucleolar size and promote localization of box C/D snoRNPs to nucleoli, suggesting a role in rRNA maturation. Inactivation of let-363/TOR or ruvb-1 suppresses the lethality associated with reduced pha-4 activity. The CeTOR pathway controls protein homeostasis and also contributes to adult longevity. We find that pha-4 is required to extend adult lifespan in response to reduced CeTOR signaling. Mutations in the predicted CeTOR target rsks-1/S6 kinase or in ife-2/eIF4E also reduce protein biosynthesis and extend lifespan, but only rsks-1 mutations require pha-4 for adult longevity. In addition, rsks-1, but not ife-2, can suppress the larval lethality associated with pha-4 loss-of-function mutations. CONCLUSIONS The data suggest that pha-4 and the CeTOR pathway antagonize one another to regulate postembryonic development and adult longevity. We suggest a model in which nutrients promote TOR and S6 kinase signaling, which represses pha-4/FoxA, leading to a shorter lifespan. A similar regulatory hierarchy may function in other animals to modulate metabolism, longevity, or disease.
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Affiliation(s)
- Karyn L Sheaffer
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112, USA
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59
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Cvacková Z, Albring KF, Koberna K, Ligasová A, Huber O, Raska I, Stanek D. Pontin is localized in nucleolar fibrillar centers. Chromosoma 2008; 117:487-97. [PMID: 18548265 DOI: 10.1007/s00412-008-0170-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2007] [Revised: 05/14/2008] [Accepted: 05/14/2008] [Indexed: 11/26/2022]
Abstract
Pontin is a multifunctional protein having roles in various cellular processes including regulation of gene expression. Here, we addressed Pontin intracellular localization using two different monoclonal antibodies directed against different Pontin epitopes. For the first time, Pontin was directly visualized in nucleoli where it co-localizes with Upstream Binding Factor and RNA polymerase I. Nucleolar localization of Pontin was confirmed by its detection in nucleolar extracts and by electron microscopy, which revealed Pontin accumulation specifically in the nucleolar fibrillar centers. Pontin localization in the nucleolus was dynamic and Pontin accumulated in large nucleolar dots mainly during S-phase. Pontin concentration in the large nucleolar dots correlated with reduced transcriptional activity of nucleoli. In addition, Pontin was found to associate with RNA polymerase I and to interact in a complex with c-Myc with rDNA sequences indicating that Pontin is involved in the c-Myc-dependent regulation of rRNA synthesis.
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Affiliation(s)
- Zuzana Cvacková
- Institute of Cellular Biology and Pathology, 1st Faculty of Medicine, Charles University in Prague, Albertov 4, 128 00 Prague 2, Czech Republic
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60
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Ducat D, Kawaguchi SI, Liu H, Yates JR, Zheng Y. Regulation of microtubule assembly and organization in mitosis by the AAA+ ATPase Pontin. Mol Biol Cell 2008; 19:3097-110. [PMID: 18463163 DOI: 10.1091/mbc.e07-11-1202] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
To identify novel proteins important for microtubule assembly in mitosis, we have used a centrosome-based complementation assay to enrich for proteins with mitotic functions. An RNA interference (RNAi)-based screen of these proteins allowed us to uncover 13 novel mitotic regulators. We carried out in-depth analyses of one of these proteins, Pontin, which is known to have several functions in interphase, including chromatin remodeling, DNA repair, and transcription. We show that reduction of Pontin by RNAi resulted in defects in spindle assembly in Drosophila S2 cells and in several mammalian tissue culture cell lines. Further characterization of Pontin in Xenopus egg extracts demonstrates that Pontin interacts with the gamma tubulin ring complex (gamma-TuRC). Because depletion of Pontin leads to defects in the assembly and organization of microtubule arrays in egg extracts, our studies suggest that Pontin has a mitosis-specific function in regulating microtubule assembly.
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Affiliation(s)
- Daniel Ducat
- Department of Embryology, Carnegie Institution for Science and Howard Hughes Medical Institute, Baltimore, MD 21210, USA
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61
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Decatur WA, Schnare MN. Different mechanisms for pseudouridine formation in yeast 5S and 5.8S rRNAs. Mol Cell Biol 2008; 28:3089-100. [PMID: 18332121 PMCID: PMC2423156 DOI: 10.1128/mcb.01574-07] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2007] [Revised: 10/23/2007] [Accepted: 02/26/2008] [Indexed: 12/29/2022] Open
Abstract
The selection of sites for pseudouridylation in eukaryotic cytoplasmic rRNA occurs by the base pairing of the rRNA with specific guide sequences within the RNA components of box H/ACA small nucleolar ribonucleoproteins (snoRNPs). Forty-four of the 46 pseudouridines (Psis) in the cytoplasmic rRNA of Saccharomyces cerevisiae have been assigned to guide snoRNAs. Here, we examine the mechanism of Psi formation in 5S and 5.8S rRNA in which the unassigned Psis occur. We show that while the formation of the Psi in 5.8S rRNA is associated with snoRNP activity, the pseudouridylation of 5S rRNA is not. The position of the Psi in 5.8S rRNA is guided by snoRNA snR43 by using conserved sequence elements that also function to guide pseudouridylation elsewhere in the large-subunit rRNA; an internal stem-loop that is not part of typical yeast snoRNAs also is conserved in snR43. The multisubstrate synthase Pus7 catalyzes the formation of the Psi in 5S rRNA at a site that conforms to the 7-nucleotide consensus sequence present in other substrates of Pus7. The different mechanisms involved in 5S and 5.8S rRNA pseudouridylation, as well as the multiple specificities of the individual trans factors concerned, suggest possible roles in linking ribosome production to other processes, such as splicing and tRNA synthesis.
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MESH Headings
- Ascomycota/genetics
- Ascomycota/metabolism
- Base Sequence
- DNA Primers/genetics
- Gene Deletion
- Genes, Fungal
- Genetic Complementation Test
- Hydro-Lyases/genetics
- Hydro-Lyases/metabolism
- Microtubule-Associated Proteins/genetics
- Microtubule-Associated Proteins/metabolism
- Molecular Sequence Data
- Nucleic Acid Conformation
- Pseudouridine/metabolism
- RNA, Fungal/chemistry
- RNA, Fungal/genetics
- RNA, Fungal/metabolism
- RNA, Ribosomal, 5.8S/chemistry
- RNA, Ribosomal, 5.8S/genetics
- RNA, Ribosomal, 5.8S/metabolism
- RNA, Ribosomal, 5S/chemistry
- RNA, Ribosomal, 5S/genetics
- RNA, Ribosomal, 5S/metabolism
- RNA, Small Nucleolar/genetics
- RNA, Small Nucleolar/metabolism
- Ribonucleoproteins, Small Nuclear/genetics
- Ribonucleoproteins, Small Nuclear/metabolism
- Saccharomyces cerevisiae/genetics
- Saccharomyces cerevisiae/metabolism
- Saccharomyces cerevisiae Proteins/genetics
- Saccharomyces cerevisiae Proteins/metabolism
- Sequence Homology, Nucleic Acid
- Spliceosomes/metabolism
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Affiliation(s)
- Wayne A Decatur
- Department of Biochemistry and Molecular Biology, 903 Lederle Graduate Research Tower, University of Massachusetts, Amherst, MA 01003, USA.
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62
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Identification of genes that function in the biogenesis and localization of small nucleolar RNAs in Saccharomyces cerevisiae. Mol Cell Biol 2008; 28:3686-99. [PMID: 18378690 DOI: 10.1128/mcb.01115-07] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Small nucleolar RNAs (snoRNAs) orchestrate the modification and cleavage of pre-rRNA and are essential for ribosome biogenesis. Recent data suggest that after nucleoplasmic synthesis, snoRNAs transiently localize to the Cajal body (in plant and animal cells) or the homologous nucleolar body (in budding yeast) for maturation and assembly into snoRNPs prior to accumulation in their primary functional site, the nucleolus. However, little is known about the trans-acting factors important for the intranuclear trafficking and nucleolar localization of snoRNAs. Here, we describe a large-scale genetic screen to identify proteins important for snoRNA transport in Saccharomyces cerevisiae. We performed fluorescence in situ hybridization analysis to visualize U3 snoRNA localization in a collection of temperature-sensitive yeast mutants. We have identified Nop4, Prp21, Tao3, Sec14, and Htl1 as proteins important for the proper localization of U3 snoRNA. Mutations in genes encoding these proteins lead to specific defects in the targeting or retention of the snoRNA to either the nucleolar body or the nucleolus. Additional characterization of the mutants revealed impairment in specific steps of U3 snoRNA processing, demonstrating that snoRNA maturation and trafficking are linked processes.
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63
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Boulon S, Marmier-Gourrier N, Pradet-Balade B, Wurth L, Verheggen C, Jády BE, Rothé B, Pescia C, Robert MC, Kiss T, Bardoni B, Krol A, Branlant C, Allmang C, Bertrand E, Charpentier B. The Hsp90 chaperone controls the biogenesis of L7Ae RNPs through conserved machinery. ACTA ACUST UNITED AC 2008; 180:579-95. [PMID: 18268104 PMCID: PMC2234240 DOI: 10.1083/jcb.200708110] [Citation(s) in RCA: 177] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
RNA-binding proteins of the L7Ae family are at the heart of many essential ribonucleoproteins (RNPs), including box C/D and H/ACA small nucleolar RNPs, U4 small nuclear RNP, telomerase, and messenger RNPs coding for selenoproteins. In this study, we show that Nufip and its yeast homologue Rsa1 are key components of the machinery that assembles these RNPs. We observed that Rsa1 and Nufip bind several L7Ae proteins and tether them to other core proteins in the immature particles. Surprisingly, Rsa1 and Nufip also link assembling RNPs with the AAA + adenosine triphosphatases hRvb1 and hRvb2 and with the Hsp90 chaperone through two conserved adaptors, Tah1/hSpagh and Pih1. Inhibition of Hsp90 in human cells prevents the accumulation of U3, U4, and telomerase RNAs and decreases the levels of newly synthesized hNop58, hNHP2, 15.5K, and SBP2. Thus, Hsp90 may control the folding of these proteins during the formation of new RNPs. This suggests that Hsp90 functions as a master regulator of cell proliferation by allowing simultaneous control of cell signaling and cell growth.
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Affiliation(s)
- Séverine Boulon
- Institute of Molecular Genetics of Montpellier, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5535, Montpellier Cedex 5, France
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64
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Zhao R, Kakihara Y, Gribun A, Huen J, Yang G, Khanna M, Costanzo M, Brost RL, Boone C, Hughes TR, Yip CM, Houry WA. Molecular chaperone Hsp90 stabilizes Pih1/Nop17 to maintain R2TP complex activity that regulates snoRNA accumulation. ACTA ACUST UNITED AC 2008; 180:563-78. [PMID: 18268103 PMCID: PMC2234237 DOI: 10.1083/jcb.200709061] [Citation(s) in RCA: 144] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Hsp90 is a highly conserved molecular chaperone that is involved in modulating a multitude of cellular processes. In this study, we identify a function for the chaperone in RNA processing and maintenance. This functionality of Hsp90 involves two recently identified interactors of the chaperone: Tah1 and Pih1/Nop17. Tah1 is a small protein containing tetratricopeptide repeats, whereas Pih1 is found to be an unstable protein. Tah1 and Pih1 bind to the essential helicases Rvb1 and Rvb2 to form the R2TP complex, which we demonstrate is required for the correct accumulation of box C/D small nucleolar ribonucleoproteins. Together with the Tah1 cofactor, Hsp90 functions to stabilize Pih1. As a consequence, the chaperone is shown to affect box C/D accumulation and maintenance, especially under stress conditions. Hsp90 and R2TP proteins are also involved in the proper accumulation of box H/ACA small nucleolar RNAs.
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Affiliation(s)
- Rongmin Zhao
- Department of Biochemistry, University of Toronto, Toronto, Ontario M5S 1A8, Canada
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65
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Yeast Rvb1 and Rvb2 are ATP-Dependent DNA Helicases that Form a Heterohexameric Complex. J Mol Biol 2008; 376:1320-33. [DOI: 10.1016/j.jmb.2007.12.049] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2007] [Revised: 12/17/2007] [Accepted: 12/19/2007] [Indexed: 11/20/2022]
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66
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McKeegan KS, Debieux CM, Boulon S, Bertrand E, Watkins NJ. A dynamic scaffold of pre-snoRNP factors facilitates human box C/D snoRNP assembly. Mol Cell Biol 2007; 27:6782-93. [PMID: 17636026 PMCID: PMC2099223 DOI: 10.1128/mcb.01097-07] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The box C/D small nucleolar RNPs (snoRNPs) are essential for the processing and modification of rRNA. The core box C/D proteins are restructured during human U3 box C/D snoRNP biogenesis; however, the molecular basis of this is unclear. Here we show that the U8 snoRNP is also restructured, suggesting that this may occur with all box C/D snoRNPs. We have characterized four novel human biogenesis factors (BCD1, NOP17, NUFIP, and TAF9) which, along with the ATPases TIP48 and TIP49, are likely to be involved in the formation of the pre-snoRNP. We have analyzed the in vitro protein-protein interactions between the assembly factors and core box C/D proteins. Surprisingly, this revealed few interactions between the individual core box C/D proteins. However, the novel biogenesis factors and TIP48 and TIP49 interacted with one or more of the core box C/D proteins, implying that they mediate the assembly of the pre-snoRNP. Consistent with this, we show that NUFIP bridges interactions between the core box C/D proteins in a partially reconstituted pre-snoRNP. Restructuring of the core complex probably reflects the conversion of the pre-snoRNP, where core protein-protein interactions are maintained by the bridging biogenesis factors, to the mature snoRNP.
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Affiliation(s)
- Kenneth Scott McKeegan
- Institute for Cell and Molecular Biosciences, University of Newcastle upon Tyne, Newcastle upon Tyne, UK
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67
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Terns M, Terns R. Noncoding RNAs of the H/ACA family. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2007; 71:395-405. [PMID: 17381322 DOI: 10.1101/sqb.2006.71.034] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
The H/ACA RNAs are an abundant family of trans-acting, noncoding RNAs found in eukaryotes and archaea. More than 100 H/ACA RNAs are known to exist in humans. The function of the majority of the identified H/ACA RNAs is to guide sites-pecific pseudouridylation of ribosomal RNA. In eukaryotes, H/ACA RNAs also mediate the processing of pre-rRNA, provide the template for telomere synthesis, and guide pseudouridylation of other classes of target RNAs (e.g., small nuclear RNAs [snRNAs]). Thus, currently, the H/ACA RNAs are known to be integrally involved in the production of both ribosomes and spliceosomes, and in the maintenance of chromosome integrity. In addition, dozens of H/ACA RNAs have been identified for which no function has yet been determined. The H/ACA RNAs select and present substrate molecules via base pairing. All H/ACA RNAs contain conserved sequence elements (box H and box ACA) and assemble with a core set of four proteins to form functional ribonucleoprotein complexes (RNPs). Mutations in key RNA and protein components of H/ACA RNPs result in dyskeratosis congenita, a serious multisystem genetic disease. Impressive progress has been made very recently in understanding the biogenesis, trafficking, and function of H/ACA RNPs.
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Affiliation(s)
- M Terns
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia 30602, USA
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68
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Matera AG, Terns RM, Terns MP. Non-coding RNAs: lessons from the small nuclear and small nucleolar RNAs. Nat Rev Mol Cell Biol 2007; 8:209-20. [PMID: 17318225 DOI: 10.1038/nrm2124] [Citation(s) in RCA: 552] [Impact Index Per Article: 32.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Recent advances have fuelled rapid growth in our appreciation of the tremendous number, diversity and biological importance of non-coding (nc)RNAs. Because ncRNAs typically function as ribonucleoprotein (RNP) complexes and not as naked RNAs, understanding their biogenesis is crucial to comprehending their regulation and function. The small nuclear and small nucleolar RNPs are two well studied classes of ncRNPs with elaborate assembly and trafficking pathways that provide paradigms for understanding the biogenesis of other ncRNPs.
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MESH Headings
- Animals
- Cell Nucleus/metabolism
- Humans
- Nucleic Acid Conformation
- RNA, Small Nuclear/chemistry
- RNA, Small Nuclear/genetics
- RNA, Small Nuclear/metabolism
- RNA, Small Nucleolar/chemistry
- RNA, Small Nucleolar/genetics
- RNA, Small Nucleolar/metabolism
- RNA, Untranslated/chemistry
- RNA, Untranslated/genetics
- RNA, Untranslated/metabolism
- Ribonucleoproteins, Small Nuclear/metabolism
- Ribonucleoproteins, Small Nucleolar/metabolism
- Transcription, Genetic
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Affiliation(s)
- A Gregory Matera
- Department of Genetics, Case Western Reserve University, Cleveland, Ohio 44106-4955, USA.
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69
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Gallant P. Control of transcription by Pontin and Reptin. Trends Cell Biol 2007; 17:187-92. [PMID: 17320397 DOI: 10.1016/j.tcb.2007.02.005] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2006] [Revised: 01/24/2007] [Accepted: 02/09/2007] [Indexed: 11/26/2022]
Abstract
Pontin and Reptin are two closely related members of the AAA+ family of DNA helicases. They have roles in diverse cellular processes, including the response to DNA double-strand breaks and the control of gene expression. The two proteins share residence in different multiprotein complexes, such as the Tip60, Ino80, SRCAP and Uri1 complexes in animals, which are involved (directly or indirectly) in transcriptional regulation, but they also function independently from each other. Both Reptin and Pontin repress certain transcriptional targets of Myc, but only Reptin is required for the repression of specific beta-catenin and nuclear factor-kappaB targets. Here, I review recent studies that have addressed the mechanisms of transcriptional control by Pontin and Reptin.
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Affiliation(s)
- Peter Gallant
- Zoologisches Institut, Universität Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
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70
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Radovic S, Rapisarda VA, Tosato V, Bruschi CV. Functional and comparative characterization of Saccharomyces cerevisiae RVB1 and RVB2 genes with bacterial Ruv homologues. FEMS Yeast Res 2007; 7:527-39. [PMID: 17302941 DOI: 10.1111/j.1567-1364.2006.00205.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Expression of yeast RuvB-like gene analogues of bacterial RuvB is self-regulated, as episomal overexpression of RVB1 and RVB2 decreases the expression of their chromosomal copies by 85%. Heterozygosity for either gene correlates with lower double-strand break repair of inverted-repeat DNA and decreased survival after UV irradiation, suggesting their haploinsufficiency, while overexpression of the bacterial RuvAB complex improves UV survival in yeast. Rvb2p preferentially binds artificial DNA Holiday junctions like the bacterial RuvAB complex, whereas Rvb1p binds to duplex or cruciform DNA. As both proteins also interact with chromatin, their role in recombination and repair through chromatin remodelling, and their evolutionary relationship to the bacterial homologue, is discussed.
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Affiliation(s)
- Slobodanka Radovic
- Yeast Molecular Genetics Group, ICGEB, Area Science Park - W, Trieste, Italy
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71
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Decatur WA, Liang XH, Piekna-Przybylska D, Fournier MJ. Identifying effects of snoRNA-guided modifications on the synthesis and function of the yeast ribosome. Methods Enzymol 2007; 425:283-316. [PMID: 17673089 DOI: 10.1016/s0076-6879(07)25013-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The small nucleolar RNAs (snoRNAs) are associated with proteins in ribonucleoprotein complexes called snoRNPs ("snorps"). These complexes create modified nucleotides in preribosomal RNA and other RNAs and participate in nucleolytic cleavages of pre-rRNA. The various reactions occur in site-specific fashion, and the mature rRNAs are ultimately incorporated into cytoplasmic ribosomes. Most snoRNAs exist in two structural classes, and most members in each class are involved in nucleotide modification reactions. Guide snoRNAs in the "box C/D" class target methylation of the 2'-hydroxyl moiety, to form 2'-O-methylated nucleotides (Nm), whereas guide snoRNAs in the "box H/ACA" class target specific uridines for conversion to pseudouridine (Psi). The rRNA nucleotides modified in this manner are numerous, totaling approximately 100 in yeast and twice that number in humans. Although the chemistry of the modifications and the factors involved in their formation are largely explained, very little is known about the influence of the copious snoRNA-guided nucleotide modifications on rRNA activity and ribosome function. Among eukaryotic organisms the sites of rRNA modification and the corresponding guide snoRNAs have been best characterized in S. cerevisiae, making this a model organism for analyzing the consequences of modification. This chapter presents approaches to characterizing rRNA modification effects in yeast and includes strategies for evaluating a variety of specific rRNA functions. To aid in planning, a package of bioinformatics tools is described that enables investigators to correlate guide function with targeted ribosomal sites in several contexts. Genetic procedures are presented for depleting modifications at one or more rRNA sites, including ablation of all Nm or Psi modifications made by snoRNPs, and for introducing modifications at novel sites. Methods are also included for characterizing modification effects on cell growth, antibiotic sensitivity, rRNA processing, formation of various rRNP complexes, translation activity, and rRNA structure within the ribosome.
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Affiliation(s)
- Wayne A Decatur
- Department of Biochemistry and Molecular Biology, University of Massachusetts, Amherst, MA, USA
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72
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Puri T, Wendler P, Sigala B, Saibil H, Tsaneva IR. Dodecameric structure and ATPase activity of the human TIP48/TIP49 complex. J Mol Biol 2006; 366:179-92. [PMID: 17157868 DOI: 10.1016/j.jmb.2006.11.030] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2006] [Revised: 11/04/2006] [Accepted: 11/08/2006] [Indexed: 11/25/2022]
Abstract
TIP48 and TIP49 are two related and highly conserved eukaryotic AAA(+) proteins with an essential biological function and a critical role in major pathways that are closely linked to cancer. They are found together as components of several highly conserved chromatin-modifying complexes. Both proteins show sequence homology to bacterial RuvB but the nature and mechanism of their biochemical role remain unknown. Recombinant human TIP48 and TIP49 were assembled into a stable high molecular mass equimolar complex and tested for activity in vitro. TIP48/TIP49 complex formation resulted in synergistic increase in ATPase activity but ATP hydrolysis was not stimulated in the presence of single-stranded, double-stranded or four-way junction DNA and no DNA helicase or branch migration activity could be detected. Complexes with catalytic defects in either TIP48 or TIP49 had no ATPase activity showing that both proteins within the TIP48/TIP49 complex are required for ATP hydrolysis. The structure of the TIP48/TIP49 complex was examined by negative stain electron microscopy. Three-dimensional reconstruction at 20 A resolution revealed that the TIP48/TIP49 complex consisted of two stacked hexameric rings with C6 symmetry. The top and bottom rings showed substantial structural differences. Interestingly, TIP48 formed oligomers in the presence of adenine nucleotides, whilst TIP49 did not. The results point to biochemical differences between TIP48 and TIP49, which may explain the structural differences between the two hexameric rings and could be significant for specialised functions that the proteins perform individually.
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Affiliation(s)
- Teena Puri
- Department of Biochemistry and Molecular Biology, University College London, London WC1E 6BT, UK
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73
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Matias PM, Gorynia S, Donner P, Carrondo MA. Crystal structure of the human AAA+ protein RuvBL1. J Biol Chem 2006; 281:38918-29. [PMID: 17060327 DOI: 10.1074/jbc.m605625200] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
RuvBL1 is an evolutionarily highly conserved eukaryotic protein belonging to the AAA(+)-family of ATPases (ATPase associated with diverse cellular activities). It plays important roles in essential signaling pathways such as the c-Myc and Wnt pathways in chromatin remodeling, transcriptional and developmental regulation, and DNA repair and apoptosis. Herein we present the three-dimensional structure of the selenomethionine variant of human RuvBL1 refined using diffraction data to 2.2A of resolution. The crystal structure of the hexamer is formed of ADP-bound RuvBL1 monomers. The monomers contain three domains, of which the first and the third are involved in ATP binding and hydrolysis. Although it has been shown that ATPase activity of RuvBL1 is needed for several in vivo functions, we could only detect a marginal activity with the purified protein. Structural homology and DNA binding studies demonstrate that the second domain, which is unique among AAA(+) proteins and not present in the bacterial homolog RuvB, is a novel DNA/RNA-binding domain. We were able to demonstrate that RuvBL1 interacted with single-stranded DNA/RNA and double-stranded DNA. The structure of the RuvBL1.ADP complex, combined with our biochemical results, suggest that although RuvBL1 has all the structural characteristics of a molecular motor, even of an ATP-driven helicase, one or more as yet undetermined cofactors are needed for its enzymatic activity.
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Affiliation(s)
- Pedro M Matias
- Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Apartado 127, 2781-901 Oeiras, Portugal
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74
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Gagnon KT, Zhang X, Agris PF, Maxwell ES. Assembly of the archaeal box C/D sRNP can occur via alternative pathways and requires temperature-facilitated sRNA remodeling. J Mol Biol 2006; 362:1025-42. [PMID: 16949610 DOI: 10.1016/j.jmb.2006.07.091] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2006] [Revised: 07/21/2006] [Accepted: 07/29/2006] [Indexed: 10/24/2022]
Abstract
Archaeal dual-guide box C/D small nucleolar RNA-like RNAs (sRNAs) bind three core proteins in sequential order at both terminal box C/D and internal C'/D' motifs to assemble two ribonuclear protein (RNP) complexes active in guiding nucleotide methylation. Experiments have investigated the process of box C/D sRNP assembly and the resultant changes in sRNA structure or "remodeling" as a consequence of sRNP core protein binding. Hierarchical assembly of the Methanocaldococcus jannaschii sR8 box C/D sRNP is a temperature-dependent process with binding of L7 and Nop56/58 core proteins to the sRNA requiring elevated temperature to facilitate necessary RNA structural dynamics. Circular dichroism (CD) spectroscopy and RNA thermal denaturation revealed an increased order and stability of sRNA folded structure as a result of L7 binding. Subsequent binding of the Nop56/58 and fibrillarin core proteins to the L7-sRNA complex further remodeled sRNA structure. Assessment of sR8 guide region accessibility using complementary RNA oligonucleotide probes revealed significant changes in guide region structure during sRNP assembly. A second dual-guide box C/D sRNA from M. jannaschii, sR6, also exhibited RNA remodeling during temperature-dependent sRNP assembly, although core protein binding was affected by sR6's distinct folded structure. Interestingly, the sR6 sRNP followed an alternative assembly pathway, with both guide regions being continuously exposed during sRNP assembly. Further experiments using sR8 mutants possessing alternative guide regions demonstrated that sRNA folded structure induced by specific guide sequences impacted the sRNP assembly pathway. Nevertheless, assembled sRNPs were active for sRNA-guided methylation independent of the pathway followed. Thus, RNA remodeling appears to be a common and requisite feature of archaeal dual-guide box C/D sRNP assembly and formation of the mature sRNP can follow different assembly pathways in generating catalytically active complexes.
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MESH Headings
- Amino Acid Sequence
- Archaea/chemistry
- Archaea/genetics
- Archaea/metabolism
- Archaeal Proteins/chemistry
- Archaeal Proteins/genetics
- Archaeal Proteins/isolation & purification
- Archaeal Proteins/metabolism
- Base Sequence
- Chromatography, Affinity
- Circular Dichroism
- Methylation
- Models, Biological
- Molecular Sequence Data
- Mutation
- Nucleic Acid Conformation
- Protein Binding
- RNA, Archaeal/chemistry
- RNA, Archaeal/genetics
- RNA, Archaeal/metabolism
- RNA, Small Nucleolar/chemistry
- RNA, Small Nucleolar/genetics
- RNA, Small Nucleolar/metabolism
- Ribonucleoproteins, Small Nuclear/chemistry
- Ribonucleoproteins, Small Nuclear/genetics
- Ribonucleoproteins, Small Nuclear/metabolism
- Temperature
- RNA, Small Untranslated
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Affiliation(s)
- Keith T Gagnon
- Department of Molecular and Structural Biochemistry, North Carolina State University, Raleigh, NC 27695-7622, USA
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75
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Hirose T, Ideue T, Nagai M, Hagiwara M, Shu MD, Steitz JA. A spliceosomal intron binding protein, IBP160, links position-dependent assembly of intron-encoded box C/D snoRNP to pre-mRNA splicing. Mol Cell 2006; 23:673-84. [PMID: 16949364 DOI: 10.1016/j.molcel.2006.07.011] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2006] [Revised: 07/05/2006] [Accepted: 07/10/2006] [Indexed: 11/22/2022]
Abstract
Pre-mRNA splicing in vertebrates is molecularly linked to other processes. We previously reported that splicing is required for efficient assembly of intron-encoded box C/D small nucleolar ribonucleoprotein (snoRNP). In the spliceosomal C1 complex, snoRNP proteins efficiently assemble onto snoRNA sequences if they are located about 50 nt upstream of the intron branchpoint. Here, we identify the splicing factor responsible for coupling snoRNP assembly to intron excision. Intron binding protein (IBP) 160, a helicase-like protein previously detected in the spliceosomal C1 complex, binds the pre-mRNA in a sequence-independent manner, contacting nucleotides 33-40 upstream of the intron branch site, regardless of whether a snoRNA is present. Depletion of IBP160 abrogates snoRNP assembly in vitro. IBP160 binding directly to a snoRNA located too close to the intron branch site interferes with snoRNP assembly. Thus, IBP160 is the key factor linking snoRNP biogenesis and perhaps other postsplicing events to pre-mRNA splicing.
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Affiliation(s)
- Tetsuro Hirose
- Biological Information Research Center, National Institute of Advanced Industrial Science and Technology, Tokyo, 135-0064, Japan.
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76
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Hoareau-Aveilla C, Bonoli M, Caizergues-Ferrer M, Henry Y. hNaf1 is required for accumulation of human box H/ACA snoRNPs, scaRNPs, and telomerase. RNA (NEW YORK, N.Y.) 2006; 12:832-40. [PMID: 16601202 PMCID: PMC1440901 DOI: 10.1261/rna.2344106] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The human telomerase ribonucleoprotein particle (RNP) shares with box H/ACA small Cajal body (sca)RNPs and small nucleolar (sno)RNPs the proteins dyskerin, hGar1, hNhp2, and hNop10. How dyskerin, hGar1, hNhp2, and hNop10 assemble with box H/ACA scaRNAs, snoRNAs, and the RNA component of telomerase (hTR) in vivo remains unknown. In yeast, Naf1p interacts with H/ACA snoRNP proteins and may promote assembly of Cbf5p (the yeast ortholog of dyskerin) with nascent pre-snoRNAs. Here we show that the human HsQ96HR8 protein, thereafter termed hNaf1, can functionally replace endogenous Naf1p in yeast. HeLa hNaf1 associates with dyskerin and hNop10 as well as box H/ACA scaRNAs, snoRNAs, and hTR. Reduction of hNaf1 steady-state levels by RNAi significantly lowers accumulation of these components of box H/ACA scaRNP, snoRNP, and telomerase. hNaf1 is found predominantly in numerous discrete foci in the nucleoplasm and fails to accumulate within Cajal bodies or nucleoli. Altogether, these results suggest that hNaf1 intervenes in early assembly steps of human box H/ACA RNPs, including telomerase.
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Affiliation(s)
- Coralie Hoareau-Aveilla
- Equipe Labellisée Ligue Nationale contre le Cancer, Laboratoire de Biologie Moléculaire Eucaryote, UMR5099 CNRS-Université Paul Sabatier, Toulouse, France, European Union
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77
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Abstract
Each of the many different box H/ACA ribonucleoprotein particles (RNPs) present in eukaryotes and archaea consists of four common core proteins and one specific H/ACA small RNA, which bears the sequence elements H (ANANNA) and ACA. Most of the H/ACA RNPs are small nucleolar RNPs (snoRNPs), which are localized in nucleoli, and are one of the two major classes of snoRNPs. Most H/ACA RNPs direct pseudouridine synthesis in pre-rRNA and other RNAs. One H/ACA small nucleolar RNA (snoRNA), vertebrate E1/U17 (snR30 in yeast), is required for pre-rRNA cleavage processing that generates mature 18S rRNA. E1 snoRNA is encoded in introns of protein-coding genes, and the evidence suggests that human E1 RNA undergoes uridine insertional RNA editing. The vertebrate E1 RNA consensus secondary structure shows several features that are absent in other box H/ACA snoRNAs. The available UV-induced RNA-protein crosslinking results suggest that the E1 snoRNP is asymmetrical in vertebrate cells, in contrast to other H/ACA snoRNPs. The vertebrate E1 snoRNP in cells is surprisingly complex: (i) E1 RNA contacts directly and specifically several proteins which do not appear to be any of the H/ACA RNP four core proteins; and (ii) multiple E1 RNA sites are needed for E1 snoRNP formation, E1 RNA stability, and E1 RNA-protein direct interactions.
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Affiliation(s)
- George L Eliceiri
- Department of Pathology, St. Louis University School of Medicine, St. Louis, Missouri 63104-1028, USA.
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78
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Mizuno K, Tokumasu A, Nakamura A, Hayashi Y, Kojima Y, Kohri K, Noce T. Genes associated with the formation of germ cells from embryonic stem cells in cultures containing different glucose concentrations. Mol Reprod Dev 2006; 73:437-45. [PMID: 16425234 DOI: 10.1002/mrd.20395] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
In a previous study, we established a system for visualizing the development of germ cells from mouse embryonic stem (ES) cells in culture using knock-in ES clones in which visual reporter genes were expressed from the mouse vasa homolog, Mvh. While assessing various culture conditions, we found that germ-cell formation was markedly depressed in low glucose medium. Using a repeated polymerase chain reaction (PCR) subtraction method, we identified genes that were differentially expressed in low versus high glucose media. Three genes that were predominantly expressed in high glucose medium, thioredoxin-interacting protein (Txnip), pituitary tumor-transforming gene 1 (Pttg), and RuvB-like protein 2 (RuvBl2), were further investigated. These genes were also found to be highly expressed in adult and embryonic gonads, and RuvBl2 in particular, which encodes an ATP-dependent DNA helicase, was specifically detected in the spermatocytes and spermatids of the adult testis as well as in primordial germ cells. Furthermore, using a green fluorescent protein (GFP) fusion construct, we found that RuvBl2 was expressed in both the nucleus and cytoplasm of testicular germ cells. These findings suggest a possible relationship between glucose metabolism and germ-cell development.
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Affiliation(s)
- Kentaro Mizuno
- Mitsubishi Kagaku Institute of Life Sciences, Minami-Ooya, Machida, Tokyo, Japan
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79
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Kiss T, Fayet E, Jády BE, Richard P, Weber M. Biogenesis and intranuclear trafficking of human box C/D and H/ACA RNPs. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2006; 71:407-17. [PMID: 17381323 DOI: 10.1101/sqb.2006.71.025] [Citation(s) in RCA: 133] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Box C/D and H/ACA snoRNAs represent two abundant groups of small noncoding RNAs. The majority of box C/D and H/ACA snoRNAs function as guide RNAs in the site-specific 2'-O-methylation and pseudouridylation of rRNAs, respectively. The box C/D snoRNAs associate with fibrillarin, Nop56, Nop58, and 15.5K/NHPX proteins to form functional snoRNP particles, whereas all box H/ACA snoRNAs form complexes with the dyskerin, Nop10, Nhp2, and Gar1 snoRNP proteins. Recent studies demonstrate that the biogenesis of mammalian snoRNPs is a complex process that requires numerous trans-acting factors. Most vertebrate snoRNAs are posttranscriptionally processed from pre-mRNA introns, and the early steps of snoRNP assembly are physically and functionally coupled with the synthesis or splicing of the host pre-mRNA. The maturing snoRNPs follow a complicated intranuclear trafficking process that is directed by transport factors also involved in nucleocytoplasmic RNA transport. The human telomerase RNA (hTR) carries a box H/ACA RNA domain that shares a common Cajal-body-specific localization element with a subclass of box H/ACA RNAs, which direct pseudouridylation of spliceosomal snRNAs in the Cajal body. However, besides concentrating in Cajal bodies, hTR also accumulates at a small, structurally distinct subset of telomeres during S phase. This suggests that a cell-cycle-dependent, dynamic localization of hTR to telomeres may play an important regulatory role in human telomere synthesis.
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MESH Headings
- Active Transport, Cell Nucleus
- Coiled Bodies/metabolism
- Humans
- Introns
- Models, Biological
- Nucleic Acid Conformation
- RNA/genetics
- RNA/metabolism
- RNA Polymerase II/metabolism
- RNA Splicing
- RNA, Small Nucleolar/chemistry
- RNA, Small Nucleolar/genetics
- RNA, Small Nucleolar/metabolism
- Ribonucleoproteins/chemistry
- Ribonucleoproteins/genetics
- Ribonucleoproteins/metabolism
- Ribonucleoproteins, Small Nucleolar/chemistry
- Ribonucleoproteins, Small Nucleolar/genetics
- Ribonucleoproteins, Small Nucleolar/metabolism
- Telomerase/genetics
- Telomerase/metabolism
- Transcription, Genetic
- RNA, Small Untranslated
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Affiliation(s)
- T Kiss
- Laboratoire de Biologie Moléculaire Eucaryote du CNRS, UMR5099, IFR109, Toulouse, France
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80
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Sigala B, Edwards M, Puri T, Tsaneva IR. Relocalization of human chromatin remodeling cofactor TIP48 in mitosis. Exp Cell Res 2005; 310:357-69. [PMID: 16157330 DOI: 10.1016/j.yexcr.2005.07.030] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2005] [Revised: 07/23/2005] [Accepted: 07/29/2005] [Indexed: 11/19/2022]
Abstract
TIP48 is a highly conserved eukaryotic AAA+ protein which is an essential cofactor for several complexes involved in chromatin acetylation and remodeling, transcriptional and developmental regulation and nucleolar organization and trafficking. We show that TIP48 abundance in HeLa cells did not change during the cell cycle, nor did its distribution in various biochemical fractions. However, we observed distinct changes in the subcellular localization of TIP48 during M phase using immunofluorescence microscopy. Our studies demonstrate that in interphase cells TIP48 was found mainly in the nucleus and exhibited a distinct localization in the nuclear periphery. As the cells entered mitosis, TIP48 was excluded from the condensing chromosomes but showed association with the mitotic apparatus. During anaphase, some TIP48 was detected in the centrosome colocalizing with tubulin but the strongest staining appeared in the mitotic equator associated with the midzone central spindle. Accumulation of TIP48 in the midzone and the midbody was observed in late telophase and cytokinesis. This redeployment of TIP48 during anaphase and cytokinesis was independent of microtubule assembly. The relocation of endogenous TIP48 to the midzone/midbody under physiological conditions suggests a novel and distinct function for TIP48 in mitosis and possible involvement in the exit of mitosis.
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Affiliation(s)
- Barbara Sigala
- Department of Biochemistry and Molecular Biology, University College London, London WC1E 6BT, UK
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81
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Yang PK, Hoareau C, Froment C, Monsarrat B, Henry Y, Chanfreau G. Cotranscriptional recruitment of the pseudouridylsynthetase Cbf5p and of the RNA binding protein Naf1p during H/ACA snoRNP assembly. Mol Cell Biol 2005; 25:3295-304. [PMID: 15798213 PMCID: PMC1069627 DOI: 10.1128/mcb.25.8.3295-3304.2005] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
H/ACA small nucleolar ribonucleoprotein particles (snoRNPs) are essential for the maturation and pseudouridylation of the precursor of rRNAs and other stable RNAs. Although the RNA and protein components of these RNPs have been identified, the mechanisms by which they are assembled in vivo are poorly understood. Here we show that the RNA binding protein Naf1p, which is required for H/ACA snoRNPs stability, associates with RNA polymerase II-associated proteins Spt16p, Tfg1p, and Sub1p and with H/ACA snoRNP proteins. Chromatin immunoprecipitation experiments show that Naf1p and the pseudouridylsynthetase Cbf5p cross-link specifically with the chromatin of H/ACA small nucleolar RNA (snoRNA) genes. Naf1p and Cbf5p cross-link predominantly with the 3' end of these genes, in a pattern similar to that observed for transcription elongation factor Spt16p. Cross-linking of Naf1p to H/ACA snoRNA genes requires active transcription and intact H/ACA snoRNA sequences but does not require the RNA polymerase II CTD kinase Ctk1p. These results suggest that Naf1p and Cbf5p are recruited in a cotranscriptional manner during H/ACA snoRNP assembly, possibly by binding to the nascent H/ACA snoRNA transcript during elongation or termination of transcription of H/ACA snoRNA genes.
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Affiliation(s)
- Pok Kwan Yang
- Department of Chemistry and Biochemistry and Molecular Biology Institute, UCLA, Box 951569, Los Angeles, CA 90095-1569, USA
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82
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de Turris V, Di Leva G, Caldarola S, Loreni F, Amaldi F, Bozzoni I. TOP promoter elements control the relative ratio of intron-encoded snoRNA versus spliced mRNA biosynthesis. J Mol Biol 2004; 344:383-94. [PMID: 15522292 DOI: 10.1016/j.jmb.2004.09.049] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2004] [Revised: 09/02/2004] [Accepted: 09/21/2004] [Indexed: 12/01/2022]
Abstract
In vertebrates almost all snoRNAs are encoded in introns of a specific subclass of polII transcripts: the TOP genes. The majority of these RNAs originate through debranching of the spliced introns, the rest through endonucleolytic cleavage of the precursor that contains them. In both cases it has been suggested that snoRNP factors associate at early steps during transcription and control snoRNA biogenesis. Here, we analyzed the specific case of the U16 snoRNA that was shown to originate mainly through endonucleolytic cleavage. We show that TOP promoter elements determine a specific ratio of snoRNA and mRNA production. Under the control of these sequences the snoRNA is likely to originate from both splicing and cleavage of the pre-mRNA. Conversely, canonical polII promoter elements seem not to be compatible with snoRNA release through the cleavage reaction and produce a lower snoRNA/mRNA ratio. In addition, we show that the proximal part of the TOP promoter is responsible for this peculiar post-transcriptional process that controls the relative ratio between snoRNA and mRNA.
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Affiliation(s)
- Valeria de Turris
- Institute Pasteur Cenci-Bolognetti, Department of Genetics and Molecular Biology, University "La Sapienza" P.le A. Moro 5, 00185 Rome, Italy
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83
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Jónsson ZO, Jha S, Wohlschlegel JA, Dutta A. Rvb1p/Rvb2p recruit Arp5p and assemble a functional Ino80 chromatin remodeling complex. Mol Cell 2004; 16:465-77. [PMID: 15525518 DOI: 10.1016/j.molcel.2004.09.033] [Citation(s) in RCA: 154] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2004] [Revised: 06/03/2004] [Accepted: 08/18/2004] [Indexed: 01/25/2023]
Abstract
The Rvb1p and Rvb2p (or TIP48 and TIP49) nuclear ATP binding proteins are universally conserved in eukaryotes and essential for viability of yeasts. Rvbp associate with each other as a double hexamer, with YHR034c and with two complexes involved in chromatin remodeling, Ino80.com and Swr1.com. Loss of Rvb1p or Ino80p affects many yeast promoters similarly. Rvbp are not essential for the recruitment of Ino80p to promoters but are essential for the catalytic activity of Ino80.com. Loss of Rvbp leads to loss of the functionally critical Arp5p in Ino80.com. Rvb2p associates with Arp5p in vitro in a reaction dependent on the presence of ATP and Ino80p. Therefore, Rvbp are required for the structural and functional integrity of the Ino80 chromatin remodeling complex.
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Affiliation(s)
- Zophonías O Jónsson
- University of Virginia School of Medicine, Jordan 1240, 1300 Jefferson Park Avenue, Charlottesville, VA 22908, USA
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84
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Watkins NJ, Lemm I, Ingelfinger D, Schneider C, Hossbach M, Urlaub H, Lührmann R. Assembly and Maturation of the U3 snoRNP in the Nucleoplasm in a Large Dynamic Multiprotein Complex. Mol Cell 2004; 16:789-98. [PMID: 15574333 DOI: 10.1016/j.molcel.2004.11.012] [Citation(s) in RCA: 134] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2004] [Revised: 09/01/2004] [Accepted: 10/05/2004] [Indexed: 12/14/2022]
Abstract
The assembly and maturation of box C/D snoRNPs, factors essential for ribosome biogenesis, occur in the nucleoplasm. To investigate this process, we have analyzed non-snoRNP factors associated with the nucleoplasmic human U3 snoRNA. We show that both the precursor and mature length nucleoplasmic U3 snoRNAs are present in larger multiprotein complexes that contain the core box C/D proteins as well as many non-snoRNP factors linked to snoRNP assembly (TIP48, TIP49, Nopp140), RNA processing (TGS1, La, LSm4, hRrp46), and subcellular localization (CRM1, PHAX). Using RNAi, we show that most of these factors are essential for box C/D snoRNA accumulation. Furthermore, we demonstrate that the core proteins undergo a restructuring event that stabilizes their binding to the snoRNA. Importantly, restructuring, which may be mediated by the putative remodeling factor TIP49, appears to be linked to nucleolar localization. We believe that the assembly complex coordinates snoRNA processing, snoRNP assembly, restructuring, and localization.
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Affiliation(s)
- Nicholas J Watkins
- Max-Planck-Institute of Biophysical Chemistry, Am Fassberg 11, D-37070 Göttingen, Germany.
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85
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Singh SK, Gurha P, Tran EJ, Maxwell ES, Gupta R. Sequential 2'-O-methylation of archaeal pre-tRNATrp nucleotides is guided by the intron-encoded but trans-acting box C/D ribonucleoprotein of pre-tRNA. J Biol Chem 2004; 279:47661-71. [PMID: 15347671 DOI: 10.1074/jbc.m408868200] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Haloferax volcanii pre-tRNA(Trp) processing requires box C/D ribonucleoprotein (RNP)-guided 2'-O-methylation of nucleotides C34 and U39 followed by intron excision. Positioning of the box C/D guide RNA within the intron of this pre-tRNA led to the assumption that nucleotide methylation is guided by the cis-positioned box C/D RNPs. We have now investigated the mechanism of 2'-O-methylation for the H. volcanii pre-tRNA(Trp) in vitro by assembling methylation-competent box C/D RNPs on both the pre-tRNA and the excised intron (both linear and circular forms) using Methanocaldococcus jannaschii box C/D RNP core proteins. With both kinetic studies and single nucleotide substitutions of target and guide nucleotides, we now demonstrate that pre-tRNA methylation is guided in trans by the intron-encoded box C/D RNPs positioned in either another pre-tRNA(Trp) or in the excised intron. Methylation by in vitro assembled RNPs prefers but does not absolutely require Watson-Crick pairing between the guide and target nucleotides. We also demonstrate for the first time that methylation of two nucleotides guided by a single box C/D RNA is sequential, that is, box C'/D' RNP-guided U39 methylation first requires box C/D RNP-guided methylation of C34. Methylation of the two nucleotides of exogenous pre-tRNA(Trp) added to an H. volcanii cell extract also occurs sequentially and is also accomplished in trans using RNPs that pre-exist in the extract. Thus, this trans mechanism is analogous to eukaryal pre-rRNA 2'-O-methylation guided by intron-encoded but trans-acting box C/D small nucleolar RNPs. This trans mechanism could explain the observed accumulation of the excised H. volcanii pre-tRNA(Trp) intron in vivo. A trans mechanism would also eliminate the obligatory refolding of the pre-tRNA that would be required to carry out two cis-methylation reactions before pre-tRNA splicing.
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MESH Headings
- Archaeal Proteins/genetics
- Archaeal Proteins/metabolism
- Gene Expression Regulation, Archaeal
- Haloferax volcanii/genetics
- Haloferax volcanii/metabolism
- Introns
- Methylation
- Mutagenesis, Site-Directed
- Nucleic Acid Conformation
- RNA Precursors/chemistry
- RNA Precursors/metabolism
- RNA, Archaeal/chemistry
- RNA, Archaeal/metabolism
- RNA, Transfer, Trp/chemistry
- RNA, Transfer, Trp/metabolism
- Ribonucleoproteins, Small Nuclear/chemistry
- Ribonucleoproteins, Small Nuclear/genetics
- Ribonucleoproteins, Small Nuclear/metabolism
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Affiliation(s)
- Sanjay K Singh
- Department of Biochemistry and Molecular Biology, Southern Illinois University, Carbondale, Illinois 62901-4413, USA
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86
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87
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Wang C, Meier UT. Architecture and assembly of mammalian H/ACA small nucleolar and telomerase ribonucleoproteins. EMBO J 2004; 23:1857-67. [PMID: 15044956 PMCID: PMC394235 DOI: 10.1038/sj.emboj.7600181] [Citation(s) in RCA: 159] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2004] [Accepted: 03/03/2004] [Indexed: 11/08/2022] Open
Abstract
Mammalian H/ACA small nucleolar RNAs and telomerase RNA share common sequence and secondary structure motifs that form ribonucleoprotein particles (RNPs) with the same four core proteins, NAP57 (also dyskerin or in yeast Cbf5p), GAR1, NHP2, and NOP10. The assembly and molecular interactions of the components of H/ACA RNPs are unknown. Using in vitro transcription/translation in combination with immunoprecipitation of core proteins, UV-crosslinking, and electrophoretic mobility shift assays, we demonstrate the following. NOP10 associates with NAP57 as a prerequisite for NHP2 binding. Although NHP2 on its own binds RNA nonspecifically, this NAP57-NOP10-NHP2 core trimer specifically recognizes H/ACA RNAs. GAR1 associates independently with NAP57 near the pseudouridylase core of mature H/ACA RNPs. In contrast to other RNPs whose assembly is initiated by protein-RNA interactions, the four H/ACA core proteins form a protein-only particle that associates with H/ACA RNAs. Nonetheless, functional H/ACA snoRNPs assembled in cytosolic extracts are stable and do not exchange their RNA components, suggesting that new particle formation requires de novo synthesis.
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Affiliation(s)
- Chen Wang
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, NY, USA
| | - U Thomas Meier
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, NY, USA
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA. Tel.: +1 718 430 3294; Fax: +1 718 430 8996; E-mail:
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88
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Hirose T, Shu MD, Steitz JA. Splicing-dependent and -independent modes of assembly for intron-encoded box C/D snoRNPs in mammalian cells. Mol Cell 2003; 12:113-23. [PMID: 12887897 DOI: 10.1016/s1097-2765(03)00267-3] [Citation(s) in RCA: 90] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
In mammalian cells, all small nucleolar RNAs (snoRNAs) that guide rRNA modification are encoded within the introns of host genes. An optimal position about 70 nts upstream of the 3' splice site of the host intron is critical for efficient expression of box C/D snoRNAs in vivo, suggesting synergy with splicing. Here, we have used a coupled in vitro splicing-snoRNA processing system to demonstrate that assembly of box C/D snoRNP proteins is the step affected by snoRNA location, and that active splicing is essential for snoRNP assembly. Splicing blockage experiments further reveal that snoRNP proteins bind specifically at the spliceosomal C1 complex stage. In contrast, splicing-independent snoRNP assembly can occur in vitro on snoRNAs that possess stable external stems. In vivo analyses confirm that a stable stem can compensate for the unusual position of those few box C/D snoRNAs located far from the 3' splice site of their host intron.
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Affiliation(s)
- Tetsuro Hirose
- Department of Molecular Biophysics and Biochemistry, Howard Hughes Medical Institute, Yale University School of Medicine, 295 Congress Avenue, New Haven, CT 06536, USA
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89
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Ohdate H, Lim CR, Kokubo T, Matsubara K, Kimata Y, Kohno K. Impairment of the DNA binding activity of the TATA-binding protein renders the transcriptional function of Rvb2p/Tih2p, the yeast RuvB-like protein, essential for cell growth. J Biol Chem 2003; 278:14647-56. [PMID: 12576485 DOI: 10.1074/jbc.m213220200] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
In Saccharomyces cerevisiae, two highly conserved proteins, Rvb1p/Tih1p and Rvb2p/Tih2p, have been demonstrated to be major components of the chromatin-remodeling INO80 complex. The mammalian orthologues of these two proteins have been shown to physically associate with the TATA-binding protein (TBP) in vitro but not clearly in vivo. Here we show that yeast proteins interact with TBP under both conditions. To assess the functional importance of these interactions, we examined the effect of mutating both TIH2/RVB2 and SPT15, which encodes TBP, on yeast cell growth. Intriguingly, only those spt15 mutations that affected the ability of TBP to bind to the TATA box caused synthetic growth defects in a tih2-ts160 background. This suggests that Tih2p might be important in recruiting TBP to the promoter. A DNA microarray technique was used to identify genes differentially expressed in the tih2-ts160 strain grown at the restrictive temperature. Only 34 genes were significantly and reproducibly affected; some up-regulated and others down-regulated. We compared the transcription of several of these Tih2p target genes in both wild type and various mutant backgrounds. We found that the transcription of some genes depends on functions possessed by both Tih2p and TBP and that these functions are substantially impaired in the spt15/tih2-ts160 double mutants that confer synthetic growth defects.
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Affiliation(s)
- Hidezumi Ohdate
- Research and Education Center for Genetic Information, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0101, Japan
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90
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Fatica A, Dlakić M, Tollervey D. Naf1 p is a box H/ACA snoRNP assembly factor. RNA (NEW YORK, N.Y.) 2002; 8:1502-1514. [PMID: 12515383 PMCID: PMC1370356] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Box H/ACA small nucleolar ribonucleoprotein particles (snoRNPs) contain four essential proteins, Cbf5p, Gar1p, Nhp2p, and Nop10p, each of which, with the exception of Gar1p, is required for box H/ACA snoRNA accumulation. Database searches identified a novel essential protein, which we termed Naf1p, with a region of homology to the RNA-binding domain of Gar1p and other features in common with hnRNP-like proteins. Naf1p is localized to the nucleus and is not a stable component of the H/ACA snoRNPs, but it is required for the accumulation of all box H/ACA snoRNAs. This requirement is not at the level of snoRNA transcription initiation or termination. Naf1 p shows in vitro RNA-binding activity and also binds directly to Cbf5p and Nhp2p. Naf1p was shown to bind to the CTD in vivo in a two-hybrid assay, and the phosphorylated CTD, but not the nonphosphorylated CTD, was shown to precipitate tagged Naf1p from a cell lysate. We propose that Naf1 p is recruited to the CTD of RNA polymerase II and binds to nascent box H/ACA snoRNAs promoting snoRNP assembly.
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Affiliation(s)
- Alessandro Fatica
- Wellcome Trust Centre for Cell Biology, Swann Building, King's Buildings, University of Edinburgh, Edinburgh EH9 3JR, UK
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91
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Watkins NJ, Dickmanns A, Lührmann R. Conserved stem II of the box C/D motif is essential for nucleolar localization and is required, along with the 15.5K protein, for the hierarchical assembly of the box C/D snoRNP. Mol Cell Biol 2002; 22:8342-52. [PMID: 12417735 PMCID: PMC134055 DOI: 10.1128/mcb.22.23.8342-8352.2002] [Citation(s) in RCA: 167] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The 5' stem-loop of the U4 snRNA and the box C/D motif of the box C/D snoRNAs can both be folded into a similar stem-internal loop-stem structure that binds the 15.5K protein. The homologous proteins NOP56 and NOP58 and 61K (hPrp31) associate with the box C/D snoRNPs and the U4/U6 snRNP, respectively. This raises the intriguing question of how the two homologous RNP complexes specifically assemble onto similar RNAs. Here we investigate the requirements for the specific binding of the individual snoRNP proteins to the U14 box C/D snoRNPs in vitro. This revealed that the binding of 15.5K to the box C/D motif is essential for the association of the remaining snoRNP-associated proteins, namely, NOP56, NOP58, fibrillarin, and the nucleoplasmic proteins TIP48 and TIP49. Stem II of the box C/D motif, in contrast to the U4 5' stem-loop, is highly conserved, and we show that this sequence is responsible for the binding of NOP56, NOP58, fibrillarin, TIP48, and TIP49, but not of 15.5K, to the snoRNA. Indeed, the sequence of stem II was essential for nucleolar localization of U14 snoRNA microinjected into HeLa cells. Thus, the conserved sequence of stem II determines the specific assembly of the box C/D snoRNP.
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Affiliation(s)
- Nicholas J Watkins
- Max-Planck-Institut für Biophysikalische Chemie, Abteilung Zelluläre Biochemie, D-37070, Göttingen, Germany
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92
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Yang PK, Rotondo G, Porras T, Legrain P, Chanfreau G. The Shq1p.Naf1p complex is required for box H/ACA small nucleolar ribonucleoprotein particle biogenesis. J Biol Chem 2002; 277:45235-42. [PMID: 12228251 DOI: 10.1074/jbc.m207669200] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Small nucleolar ribonucleoprotein particles (snoRNPs) are essential cofactors in ribosomal RNA metabolism. Although snoRNP composition has been thoroughly characterized, the biogenesis process of these particles is poorly understood. We have identified two proteins from the yeast Saccharomyces cerevisiae, Yil104c/Shq1p and Ynl124w/Naf1p, which are essential and required for the stability of box H/ACA snoRNPs. Depletion of either Shq1p or Naf1p leads to a dramatic and specific decrease in box H/ACA snoRNA levels in vivo. A severe concomitant defect in ribosomal RNA processing is observed, consistent with the depletion of this family of snoRNAs. Shq1p and Naf1p show nuclear localization and interact with Nhp2p and Cbf5p, two core proteins of mature box H/ACA snoRNPs. Shq1p and Naf1p form a complex, but they are not strongly associated with box H/ACA snoRNPs. We propose that Shq1p and Naf1p are involved in the early biogenesis steps of box H/ACA snoRNP assembly.
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Affiliation(s)
- Pok Kwan Yang
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, UCLA, Los Angeles, California 90095-1569, USA
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93
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Dez C, Noaillac-Depeyre J, Caizergues-Ferrer M, Henry Y. Naf1p, an essential nucleoplasmic factor specifically required for accumulation of box H/ACA small nucleolar RNPs. Mol Cell Biol 2002; 22:7053-65. [PMID: 12242285 PMCID: PMC139812 DOI: 10.1128/mcb.22.20.7053-7065.2002] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Box H/ACA small nucleolar ribonucleoprotein particles (H/ACA snoRNPs) play key roles in the synthesis of eukaryotic ribosomes. The ways in which these particles are assembled and correctly localized in the dense fibrillar component of the nucleolus remain largely unknown. Recently, the essential Saccharomyces cerevisiae Naf1p protein (encoded by the YNL124W open reading frame) was found to interact in a two-hybrid assay with two core protein components of mature H/ACA snoRNPs, Cbf5p and Nhp2p (T. Ito, T. Chiba, R. Ozawa, M. Yoshida, M. Hattori, and Y. Sakaki, Proc. Natl. Acad. Sci. USA 98:4569-4574, 2001). Here we show that several H/ACA snoRNP components are weakly but specifically immunoprecipitated with epitope-tagged Naf1p, suggesting that the latter protein is involved in H/ACA snoRNP biogenesis, trafficking, and/or function. Consistent with this, we find that depletion of Naf1p leads to a defect in 18S rRNA accumulation. Naf1p is unlikely to directly assist H/ACA snoRNPs during pre-rRNA processing in the dense fibrillar component of the nucleolus for two reasons. Firstly, Naf1p accumulates predominantly in the nucleoplasm. Secondly, Naf1p sediments in a sucrose gradient chiefly as a free protein or associated in a complex of the size of free snoRNPs, whereas extremely little Naf1p is found in fractions containing preribosomes. These results are more consistent with a role for Naf1p in H/ACA snoRNP biogenesis and/or intranuclear trafficking. Indeed, depletion of Naf1p leads to a specific and dramatic decrease in the steady-state accumulation of all box H/ACA snoRNAs tested and of Cbf5p, Gar1p, and Nop10p. Naf1p is unlikely to be directly required for the synthesis of H/ACA snoRNP components. Naf1p could participate in H/ACA snoRNP assembly and/or transport.
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Affiliation(s)
- Christophe Dez
- Laboratoire de Biologie Moléculaire Eucaryote du CNRS, Université Paul Sabatier, 31062 Toulouse Cedex 04, France
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94
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Abstract
In eukaryotes, the site-specific formation of the two prevalent types of rRNA modified nucleotides, 2'-O-methylated nucleotides and pseudouridines, is directed by two large families of snoRNAs. These are termed box C/D and H/ACA snoRNAs, respectively, and exert their function through the formation of a canonical guide RNA duplex at the modification site. In each family, one snoRNA acts as a guide for one, or at most two modifications, through a single, or a pair of appropriate antisense elements. The two guide families now appear much larger than anticipated and their role not restricted to ribosome synthesis only. This is reflected by the recent detection of guides that can target other cellular RNAs, including snRNAs, tRNAs and possibly even mRNAs, and by the identification of scores of tissue-specific specimens in mammals. Recent characterization of homologs of eukaryotic modification guide snoRNAs in Archaea reveals the ancient origin of these non-coding RNA families and offers new perspectives as to their range of function.
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Affiliation(s)
- Jean Pierre Bachellerie
- Laboratoire de Biologie Moléculaire Eucaryote du CNRS, Université Paul-Sabatier, 118, route de Narbonne, 31062 Toulouse cedex 4,France.
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95
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Abstract
Eukaryotic cells contain a very complex population of small nucleolar RNAs. They function, as small nucleolar ribonucleoproteins, in pre-ribosomal RNA processing reactions, and also guide methylation and pseudouridylation of ribosomal RNA, spliceosomal small nuclear RNAs, and possibly other cellular RNAs. Synthesis of small nucleolar RNAs frequently follows unusual strategies. Some newly discovered brain-specific small nucleolar RNAs of unknown function are encoded in introns of tandemly repeated units, expression of which is paternally imprinted. Recent studies of the protein components and factors participating in small nucleolar ribonucleoprotein assembly have revealed interesting connections with other classes of cellular ribonucleoproteins such as spliceosomal small nuclear ribonucleoproteins and telomerase. Cajal bodies emerge as nuclear structures important for the biogenesis and function of small nucleolar ribonucleoproteins.
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Affiliation(s)
- Witold Filipowicz
- Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel, Switzerland.
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96
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Speckmann WA, Li ZH, Lowe TM, Eddy SR, Terns RM, Terns MP. Archaeal guide RNAs function in rRNA modification in the eukaryotic nucleus. Curr Biol 2002; 12:199-203. [PMID: 11839271 DOI: 10.1016/s0960-9822(02)00655-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
In eukaryotes, many Box C/D small nucleolar RNAs base pair with ribosomal RNA through short complementary guide sequences, thereby marking up to 100 individual nucleotides of ribosomal RNA for 2'-O-methylation. Function of the eukaryotic Box C/D RNAs depends upon interaction with at least six known proteins. Box C/D RNAs are not known to exist in Bacteria but were recently identified in Archaea by biochemical analysis and computational genomic screens and have likely evolved independently in Archaea and Eukarya for more than 2000 million years. We have microinjected Box C/D RNAs from Pyrococcus furiosus, a hyperthermophilic archaeon, into the nuclei of oocytes from the aquatic frog Xenopus laevis. Our results show that Box C/D RNAs derived from this prokaryote are retained in the nucleus, localize to nucleoli, and interact with the X. laevis Box C/D RNA binding proteins fibrillarin, Nop56, and Nop58. Furthermore, we have demonstrated the ability of archaeal Box C/D RNAs to direct site-specific 2'-O-methylation of ribosomal RNA. Our studies have revealed the remarkable ability of archaeal Box C/D RNAs to assemble into functional RNA-protein complexes in the eukaryotic nucleus.
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Affiliation(s)
- Wayne A Speckmann
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
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