Small RNAs in the nucleus and cytoplasm of hela cells

Eliceiri, George L.; Sayavedra, Marta S.

doi:10.1016/s0006-291x(76)80070-8

Cited by 76 publications

(48 citation statements)

References 15 publications

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“…Localization studies of nascent and steadystate snRNAs in mammalian cells using conventional cell fractionation procedures are largely in agreement with data from Xenopus oocytes (Eliceiri 1974;Eliceiri and Sayavedra 1976;Zieve and Penman 1976;Gurney and Eliceiri 1980), as are more recent results (Zieve et al 1988;Feeney et al 1989}. Taken together, the data argue that snRNP biogenesis in mammalian somatic cells and Xenopus oocytes is similar.…”

Section: ' Lg]gaaaa-oohsupporting

confidence: 86%

Distinct molecular signals for nuclear import of the nucleolar snRNA, U3.

Baserga¹,

Gilmore-Hebert²,

Yang³

1992

Genes Dev.

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Export to the cytoplasm of U3 RNA transcribed from a rat U3 gene injected into the nucleus of Xenopus oocytes indicates that the biogenesis of U3 RNA, like that of the previously studied Sm-precipitable nucleoplasmic snRNAs (U1, U2, U4, and US), includes a cytoplasmic phase. The regulation of import of the U3 snRNA into the nucleus has been analyzed by injection of synthetic human U3 transcripts into the cytoplasm of Xenopus oocytes. Binding of the major autoantigenic protein of the U3 snRNP, fibriUarin, and cap trimethylation can occur in the cytoplasm, but neither are required for import. The 3'-terminal 13 nucleotides are required for optimal import and cap trimethylation and participate in a phylogenetically conserved U3 structural element, a short 3'-terminal stem. An artificial construct containing the 3'-terminal 13 nucleotides, including the 3'-terminal stem, but only 56 nucleotides of the 217 nucleotides in U3, appears to be sufficient for import. The presence of the 3'-terminal stem in all snRNAs known to be imported suggests that it might be a universal element required for nuclear import.

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Section: ' Lg]gaaaa-oohsupporting

confidence: 86%

Distinct molecular signals for nuclear import of the nucleolar snRNA, U3.

Baserga¹,

Gilmore-Hebert²,

Yang³

1992

Genes Dev.

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“…Moreover, 3Ј end formation appears to be an RNA processing event, because U2 (but apparently not U1) transcription continues for up to 800 nucleotides (nt) beyond the 3Ј box (15,47). Over the next 90 min (12,51), the processed intermediate is exported to the cytoplasm, where the mature 3Ј end is generated by 3Ј trimming (21,29), the 5Ј monomethyl cap is trimethylated, Sm proteins are assembled onto the snRNA (44,45), and the nearly mature small nuclear ribonucleoprotein particle is imported back into the nucleus (31) where it undergoes further base modifications (17,71) before it can function in RNA processing. Little is known about either the nuclear or cytoplasmic 3Ј processing events, but the dependence of efficient 3Ј-box-directed processing on a PSE-bearing snRNA promoter links an early step at the promoter to later events at the 3Ј end of the gene, perhaps through specific modification of the polymerase and/or recruitment of factors that travel along with it.…”

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confidence: 99%

Role of the C-Terminal Domain of RNA Polymerase II in U2 snRNA Transcription and 3′ Processing

Jacobs

Ogiwara

Weiner

2004

Molecular and Cellular Biology

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U small nuclear RNAs (snRNAs) and mRNAs are both transcribed by RNA polymerase II (Pol II), but the snRNAs have unusual TATA-less promoters and are neither spliced nor polyadenylated; instead, 3 processing is directed by a highly conserved 3 end formation signal that requires initiation from an snRNA promoter. Here we show that the C-terminal domain (CTD) of Pol II is required for efficient U2 snRNA transcription, as it is for mRNA transcription. However, CTD kinase inhibitors, such as 5,6-dichloro-1-␤-D-ribofuranosylbenzimidazole (DRB) and 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7), that block mRNA elongation do not affect U2 transcription, although 3 processing of the U2 primary transcript is impaired. We show further that U2 transcription is preferentially inhibited by low doses of UV irradiation or actinomycin D, which induce CTD kinase activity, and that UV inhibition can be rescued by treatment with DRB or H7. We propose that Pol II complexes transcribing snRNAs and mRNAs have distinct CTD phosphorylation patterns. mRNA promoters recruit factors including kinases that hyperphosphorylate the CTD, and the CTD in turn recruits proteins needed for mRNA splicing and polyadenylation. We predict that snRNA promoters recruit factors including a CTD kinase(s) whose snRNA-specific phosphorylation pattern recruits factors required for promoter-coupled 3 end formation.RNAs that encode proteins are transcribed by RNA polymerase II (Pol II) in almost all eukaryotes. In contrast, untranslated RNAs are transcribed by all three RNA polymerases: 5.8, 18, and 28S rRNA by Pol I; 5S rRNA, tRNA, and U6 small nuclear RNA (snRNA) by Pol III (56); and the other U snRNAs, which function in mRNA splicing and various RNA processing events, by Pol II (27). Kinetoplastid protozoa, a class of early diverging eukaryotes, are exceptions to these rules. Kinetoplastid snRNAs are transcribed not by Pol II but by Pol III (65), and certain mRNAs, including the immunologically important variant surface glycoprotein message, are hybrids of a U snRNA-like spliced leader transcribed by Pol II and a protein-coding mRNA body transcribed by Pol I (19).Although U snRNAs and mRNAs are both transcribed by Pol II in mammals, the genes are very different. U snRNA promoters have no TATA box and rely instead upon a dedicated U snRNA-specific promoter consisting of a highly conserved proximal sequence element (PSE) and an enhancer-like distal sequence element spaced one nucleosome apart (27). In addition, U snRNA genes are short (typically only a few hundred base pairs) and lack introns, whereas genes encoding mRNAs can span megabases and usually contain many introns. Also, U snRNA genes are typically present in multiple copies in higher eukaryotes-the human U1 and U2 genes are tandemly repeated (6, 40, 66, 68)-whereas most protein-coding genes are present in only one or a few copies per haploid genome.U snRNA processing also differs from mRNA processing. U snRNAs are neither spliced nor polyadenylated; instead, formation of the first U snRNA interme...

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“…The small nuclear ribonucleoproteins (snRNPs) that are immunoprecipitable by the lupus Sm autoantibody specificity have been implicated in the processing of mRNA (14, 26). The snRNPs contain the snRNAs (Ul, U2, U4, U5, and U6) which are also thought to be products of RNA pol II and require trimethyl 5' capping, methylation, and excision of extraneous sequences (1,5,18,27,28,35,37). Previous work has suggested that the snRNAs are synthesized in the nucleus as precursors that are transported to the cytoplasm where they are processed to their mature sizes, assembled into RNPs, and then transported back to the nucleus (5, 6, 34, 42).…”

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confidence: 99%

Rapid inhibition of processing and assembly of small nuclear ribonucleoproteins after infection with vesicular stomatitis virus.

Fresco¹,

Kurilla²,

Keene³

1987

Mol. Cell. Biol.

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After infection of baby hamster kidney cells with vesicular stomatitis virus (VSV), processing and assembly of small nuclear ribonucleoproteins (snRNP) were rapidly inhibited. The Ul and U2 snRNAs accumulated as precursor species approximately 3 and 10 nucleotides longer, respectively, than the mature RNAs. Alteration in snRNP assembly was noted because the precursor snRNAs were not associated with the U-series RNA-core protein complex in infected cells. However, antibodies specific for the U2 RNA-binding protein, A', were able to precipitate pre-U2 RNAs from VSV-infected cells. These results indicated that precursors to U2 RNA were bound to A' and remained bound during virus infection. Analysis of the synthesis of proteins normally associated with Ul and U2 RNAs indicated that synthesis was unaffected at times when snRNP assembly with core proteins was blocked by the VSV. These findings suggested that the core proteins associate with one another in the absence of the snRNAs in VSV-infected cells. They further suggest a correlation between the inability of the core complex to bind the U-series snRNPs and the failure to process the 3' ends of Ul and U2 RNAs in VSV-infected cells. These effects of VSV on snRNP assembly may be related to the shutoff of host-cell macromolecular synthesis.Vesicular stomatitis virus (VSV) is a member of the negative-strand RNA virus group and is known to cause acute as well as persistent virus infections in a wide range of mammalian hosts (30). Acute infections are associated with dramatic alterations in cellular RNA metabolism and mRNA translation (31,36,40). Evidence from Wagner and coworkers (8,9,22) has implicated a short viral transcript, the leader RNA, in the shutoff of transcription by RNA polymerases (pol) II and III; however, the target of this interaction has not been elucidated. Although leader RNA is bound to the cellular La protein (15, 16) which, presumably, plays a role in synthesis or processing of RNA pol III transcripts (2,18,29), no evidence relating the leader-La association to the inhibition of cellular RNA synthesis has been found. In addition, Grinnell and Wagner (9) have shown that the leader RNA can bind to an unidentified cell protein of 65 kilodaltons (kDa), but the specificity and functional significance of this interaction is unknown.Most RNA pol II transcripts are processed via a complex series of reactions including capping, methylation, splicing, and polyadenylation (24). The small nuclear ribonucleoproteins (snRNPs) that are immunoprecipitable by the lupus Sm autoantibody specificity have been implicated in the processing of mRNA (14, 26). The snRNPs contain the snRNAs (Ul, U2, U4, U5, and U6) which are also thought to be products of RNA pol II and require trimethyl 5' capping, methylation, and excision of extraneous sequences (1,5,18,27,28,35,37). Previous work has suggested that the snRNAs are synthesized in the nucleus as precursors that are transported to the cytoplasm where they are processed to their mature sizes, assembled into RNPs, and then t...

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Small RNAs in the nucleus and cytoplasm of hela cells

Cited by 76 publications

References 15 publications

Distinct molecular signals for nuclear import of the nucleolar snRNA, U3.

Distinct molecular signals for nuclear import of the nucleolar snRNA, U3.

Role of the C-Terminal Domain of RNA Polymerase II in U2 snRNA Transcription and 3′ Processing

Rapid inhibition of processing and assembly of small nuclear ribonucleoproteins after infection with vesicular stomatitis virus.

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