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Eukaryotes and archaea use two sets of specialized ribonucleoproteins (RNPs) to carry out sequence-specific methylation and pseudouridylation of RNA, the two most abundant types of modifications of cellular RNAs. In eukaryotes, these protein-RNA complexes localize to the nucleolus and are called small nucleolar RNPs (snoRNPs), while in archaea they are known as small RNPs (sRNP). The C/D class of sno(s)RNPs carries out ribose-2'-O-methylation, while the H/ACA class is responsible for pseudouridylation of their RNA targets. Here, we review the recent advances in the structure, assembly and function of the conserved C/D and H/ACA sno(s)RNPs. Structures of each of the core archaeal sRNP proteins have been determined and their assembly pathways delineated. Furthermore, the recent structure of an H/ACA complex has revealed the organization of a complete sRNP. Combined with current biochemical data, these structures offer insight into the highly homologous eukaryotic snoRNPs. 相似文献
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The role of small nucleolar ribonucleoproteins in ribosome synthesis 总被引:14,自引:0,他引:14
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Human Nop5/Nop58 is a component common to the box C/D small nucleolar ribonucleoproteins 总被引:8,自引:1,他引:7 下载免费PDF全文
We have identified an apparent human homolog of the yeast Nop5/Nop58 protein. hNop5/Nop58 codes for a protein of predicted molecular weight 59.6 kDa and is 46.8% identical to Saccharomyces cerevisiae Nop5/Nop58. Immunofluorescent staining with antibodies against hNop5/Nop58 indicate that it is localized primarily to the nucleolus, and coimmunoprecipitation from nuclear extracts demonstrates that hNop5/Nop58 interacts with the box C/D family of snoRNAs. Thus, hNop5/Nop58 is a common component of the box C/D snoRNPs, and joins fibrillarin as the second such component identified and characterized in metazoans. 相似文献
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Ro small cytoplasmic ribonucleoproteins are a subclass of La ribonucleoproteins: further characterization of the Ro and La small ribonucleoproteins from uninfected mammalian cells. 总被引:73,自引:9,他引:64 下载免费PDF全文
J P Hendrick S L Wolin J Rinke M R Lerner J A Steitz 《Molecular and cellular biology》1981,1(12):1138-1149
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J. A. Makarova S. M. Ivanova A. G. Tonevitsky A. I. Grigoriev 《Biochemistry. Biokhimii?a》2013,78(6):638-650
Small nucleolar RNAs (snoRNAs) are one of the most abundant and well-studied groups of non-coding RNAs. snoRNAs are mostly engaged in processing of rRNA. However, recent data indicate that snoRNAs are also involved in other processes including regulation of alternative splicing, translation and oxidative stress. snoRNAs are also involved in pathogenesis of some hereditary diseases and cancer. Therefore, the range of snoRNAs’ functions is significantly wider than it has been assumed earlier. 相似文献
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Box C/D small nucleolar RNA trafficking involves small nucleolar RNP proteins, nucleolar factors and a novel nuclear domain 总被引:3,自引:0,他引:3
Verheggen C Mouaikel J Thiry M Blanchard JM Tollervey D Bordonné R Lafontaine DL Bertrand E 《The EMBO journal》2001,20(19):5480-5490
Nucleolar localization of box C/D small nucleolar (sno) RNAs requires the box C/D motif and, in vertebrates, involves transit through Cajal bodies (CB). We report that in yeast, overexpression of a box C/D reporter leads to a block in the localization pathway with snoRNA accumulation in a specific sub-nucleolar structure, the nucleolar body (NB). The human survival of motor neuron protein (SMN), a marker of gems/CB, specifically localizes to the NB when expressed in yeast, supporting similarities between these structures. Box C/D snoRNA accumulation in the NB was decreased by mutation of Srp40 and increased by mutation of Nsr1p, two related nucleolar proteins that are homologous to human Nopp140 and nucleolin, respectively. Box C/D snoRNAs also failed to accumulate in the NB, and became delocalized to the nucleoplasm, upon depletion of any of the core snoRNP proteins, Nop1p/fibrillarin, Snu13p, Nop56p and Nop5p/Nop58p. We conclude that snoRNP assembly occurs either in the nucleoplasm, or during transit of snoRNAs through the NB, followed by routing of the complete snoRNP to functional sites of ribosome synthesis. 相似文献
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Inactivation of cleavage factor I components Rna14p and Rna15p induces sequestration of small nucleolar ribonucleoproteins at discrete sites in the nucleus 下载免费PDF全文
Carneiro T Carvalho C Braga J Rino J Milligan L Tollervey D Carmo-Fonseca M 《Molecular biology of the cell》2008,19(4):1499-1508
Small nucleolar RNAs (snoRNAs) associate with specific proteins forming small nucleolar ribonucleoprotein (snoRNP) particles, which are essential for ribosome biogenesis. The snoRNAs are transcribed, processed, and assembled in snoRNPs in the nucleoplasm. Mature particles are then transported to the nucleolus. In yeast, 3'-end maturation of snoRNAs involves the activity of Rnt1p endonuclease and cleavage factor IA (CFIA). We report that after inhibition of CFIA components Rna14p and Rna15p, the snoRNP proteins Nop1p, Nop58p, and Gar1p delocalize from the nucleolus and accumulate in discrete nucleoplasmic foci. The U14 snoRNA, but not U3 snoRNA, similarly redistributes from the nucleolus to the nucleoplasmic foci. Simultaneous depletion of either Rna14p or Rna15p and the nuclear exosome component Rrp6p induces accumulation of poly(A)(+) RNA at the snoRNP-containing foci. We propose that the foci detected after CFIA inactivation correspond to quality control centers in the nucleoplasm. 相似文献
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Silva MT Ambrósio DL Trevelin CC Watanabe TF Laure HJ Greene LJ Rosa JC Valentini SR Cicarelli RM 《Memórias do Instituto Oswaldo Cruz》2011,106(2):130-138
Several protozoan parasites exist in the Trypanosomatidae family, including various agents of human diseases. Multiple lines of evidence suggest that important differences are present between the translational and mRNA processing (trans splicing) systems of trypanosomatids and other eukaryotes. In this context, certain small complexes of RNA and protein, which are named small nuclear ribonucleoproteins (U snRNPs), have an essential role in pre-mRNA processing, mainly during splicing. Even though they are well defined in mammals, snRNPs are still not well characterized in trypanosomatids. This study shows that a U5-15K protein is highly conserved among various trypanosomatid species. Tandem affinity pull-down assays revealed that this protein interacts with a novel U5-102K protein, which suggests the presence of a sub-complex that is potentially involved in the assembly of U4/U6-U5 tri-snRNPs. Functional analyses showed that U5-15K is essential for cell viability and is somehow involved with the trans and cis splicing machinery. Similar tandem affinity experiments with a trypanonosomatid U5-Cwc21 protein led to the purification of four U5 snRNP specific proteins and a Sm core, suggesting U5-Cwc-21 participation in the 35S U5 snRNP particle. Of these proteins, U5-200K was molecularly characterized. U5-200K has conserved domains, such as the DEAD/DEAH box helicase and Sec63 domains and displays a strong interaction with U5 snRNA. 相似文献
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Deshmukh US Kannapell CC Fu SM 《Journal of immunology (Baltimore, Md. : 1950)》2002,168(10):5326-5332
Complex patterns of autoantibody reactivities with the small nuclear ribonucleoproteins (snRNPs) are observed in systemic lupus erythematosus. To investigate the role of individual snRNP components in the initiation and diversification of anti-snRNP Ab responses, we immunized A/J mice with recombinant Smith D (SmD), Smith B (SmB), and A ribonucleoprotein (A-RNP) with alum as adjuvant. Sera at different time points after initial immunizations were analyzed by Western blot and immunoprecipitation assays. In SmD-immunized mice, specific Abs to A-RNP and SmB were generated by 2 mo postimmunization, in addition to the detection of cross-reactive Abs between the immunogen and other snRNPs. Whereas Abs reactive with the immunogen decreased by 5 mo, Abs capable of immunoprecipitating A-RNP and SmB increased. In SmB-immunized mice, specific Abs to A-RNP were readily detectable, in addition to cross-reactive Abs. In contrast, A-RNP-immunized mice had only cross-reactive Abs to SmB without detectable Abs to SmD. However, in these mice, specific Abs to the 70-kDa protein were generated. Abs, which precipitated the native snRNP particle, were generated in all three groups of the immunized mice. Our results show that different initiating Ags from the same multiprotein antigenic complex induce distinct patterns of epitope spreading to proteins within that complex. These data have significant implications for the mechanisms of autoantibody diversification in systemic lupus erythematosus. 相似文献
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Nucleoplasmic organization of small nuclear ribonucleoproteins in cultured human cells 总被引:21,自引:5,他引:16 下载免费PDF全文
《The Journal of cell biology》1993,121(4):715-727