Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.6 (RNA polymerase)
34,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The nucleoplasmic autoantigens RNP and Sm are of particular interest because of their associations with certain symptoms of mixed connective tissue disease and systemic lupus erythematosus. The RNP is generally thought to be a ribonucleoprotein and there is evidence that its RNA may be single-stranded. Experiments presented in this report are in support of the concept that the Sm-antigen may also be an RNA protein. Purified Sm-anti-Sm precipitates were shown to have high RNA contents and treatment of Sm-antigen with RNAase in a hypotonic medium strongly reduced in antigenicity. The latter effect indicates that the Sm-antigen may in contrast to the RNP contain double-stranded RNA, a possibility also suggested by the finding that the Sm-antigen was soluble in 2 M LiCl. The Sm-antigen was found further to differ from RNP in being selectively absorbed in BD-Sephadex, while RNP remained active in the supernatant. Cytochemical studies involving stimulation and inhibition experiments with lectins and RNA polymerase inhibitors showed that the Sm-antigen was, in distinction to RNP, sensitive to rifampicin but not to alpha-amanitine. This suggests that the RNAs of the nucleoplasmic antigens may be synthesized by different RNA polymerases.
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PMID:On the biochemical nature of the 'Sm' nucleoplasmic antigen. 616 74

Anti-Th serum from a patient with systemic lupus erythematosus immunoprecipitates from both human and mouse cell extracts small ribonucleoproteins containing 7-2 RNA, 8-2 RNA, and the Ro RNAs. Human 7-2 RNA, which must be complexed with protein to be antigenic, is about 300 nucleotides long and has mostly pG at its 5' end. A related 7-2 RNA, precipitated by anti-La antibody, gives identical Tl and pancreatic RNase fingerprints, but has more pppG at its 5' end. La 7-2 RNA is, therefore, likely to be a precursor of Th 7-2 RNA. The synthesis of 7-2 RNA in isolated nuclei exhibits a pattern of sensitivity to alpha-amanitin that is characteristic for RNA polymerase III transcription. Thus, 7-2 RNA can be added to the list of mammalian RNA polymerase III transcripts that initially bind the La protein and then become incorporated into other types of antigenic RNP particles.
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PMID:Sequential association of nucleolar 7-2 RNA with two different autoantigens. 618 83

We have examined some aspects of the biosynthesis of human small nuclear RNAs (snRNAs). The sensitivity of U5 and U4 snRNA synthesis to alpha-amanitin in whole cells suggests that RNA polymerase II is involved in the synthesis of these RNA species, in addition to that of U1, U2, and U3 snRNA. Two RNA bands were detected, whose properties are compatible with being U3 and U4 RNA precursors. The cytoplasmic U1 RNA precursor (pU1) was retained by an anti-RNP antibody column, while the cytoplasmic precursors to U1 and U2 (pU2) RNA were immunoprecipitated by monoclonal anti-Sm antibodies. Therefore, soon after their transcription, these cytoplasmic RNA precursors assemble with the polypeptides which bear the RNP (pU1) and Sm (pU1 and pU2) antigenic determinants. It has been shown before that, shortly after protein synthesis is interrupted, the apparent cytoplasmic leads to nuclear transition of newly made U2 RNA is inhibited, while U2 RNA transcription is not. The present data indicate that the trimming of the U2 RNA precursor to mature U2 RNA is not affected early after suppression of protein synthesis.
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PMID:Biosynthesis of small nuclear RNAs in human cells. 619 66

In the macronuclear rRNA genes of Tetrahymena thermophila, a 413 bp intervening sequence (IVS) interrupts the 26S rRNA-coding region. A restriction fragment of the rDNA containing the IVS and portions of the adjacent rRNA sequences (exons) was inserted downstream from the lac UV5 promoter in a recombinant plasmid. Transcription of this template by purified Escherichia coli RNA polymerase in vitro produced a shortened version of the pre-rRNA, which was then deproteinized. When incubated with monovalent and divalent cations and a guanosine factor, this RNA underwent splicing. The reactions that were characterized included the precise excision of the IVS, attachment of guanosine to the 5' end of the IVS, covalent cyclization of the IVS and ligation of the exons. We conclude that splicing activity is intrinsic to the structure of the RNA, and that enzymes, small nuclear RNAs and folding of the pre-rRNA into an RNP are unnecessary for these reactions. We propose that the IVS portion of the RNA has several enzyme-like properties that enable it to break and reform phosphodiester bonds. The finding of autocatalytic rearrangements of RNA molecules has implications for the mechanism and the evolution of other reactions that involve RNA.
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PMID:Self-splicing RNA: autoexcision and autocyclization of the ribosomal RNA intervening sequence of Tetrahymena. 629 45

A method is described for preparation of a fraction of chromatin enriched in transcribing regions from nuclei of mouse GR cells. This fraction, released by mild staphylococcal nuclease digestion of isolated nuclei, contains 2 to 10% of the DNA as polynucleosomal chromatin together with 50-70% of pulse-labelled RNA and about 90% of all template-engaged RNA polymerase B molecules, titrated with (3H)-alpha-amanitin. Hybridisation of DNA from this chromatin fraction to total nuclear RNA in excess shows that it is enriched in frequently-transcribed DNA sequences. A modification of the Miller technique, allowing the spreading of the active chromatin fraction for electron microscopy, has been developed. Examination of the spreads reveals that this chromatin fraction contains 20-100 nucleosome-long polynucleosomal chains bearing lateral RNP fibrils interpreted as nascent transcripts. The average length of the DNA fragments in the fraction is greater than that of average transcribed regions, suggesting that the transcribed regions are linked to flanking segments whose chromatin conformation probably contributes to the selective release of transcribing chromatin.
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PMID:Isolation and characterisation of a transcribing polynucleosomal chromatin fraction. 667 92

Adult rat hepatocytes in primary culture were used to study the effect of tryptophan pyrolysis products on the transcriptional process. Hepatocytes were treated with 1, 5 and 10 micrograms/ml of 3-amino-1,4-dimethyl-5H-pyrido-[4,3-b]-indole (Trp-P-1) or 3-amino-1-methyl-5H-pyrido-[4,3-b]-indole (Trp-P-2) for 2 and 4 h. The ultrastructural study revealed the appearance of nucleolar microsegregation accompanied by a reduction in peri- and interchromatin fibrils and granules in hepatocytes exposed to 10 micrograms/ml of each pyrolysate for 1 or 2 h. Biochemical investigation showed that the incorporation of [3H]uridine into nuclear RNA of treated hepatocytes was strongly decreased. Time- and concentration-related inhibition have been established; however, the inhibitory effect of Trp-P-1 was always superior to that of Trp-P-2. The determination of Mg2+-dependent RNA polymerase activity in an in vitro system functioning with isolated rat liver nuclei incubated in the presence of Trp-P-1 or Trp-P-2 showed a 40% inhibition of this activity. After a 1-h exposure of hepatocytes to 5 and 10 micrograms/ml of Trp-P-1, the recovery of RNA synthesis capacity was complete by 2 h and that of normal ultrastructural aspect was achieved within 4 h. All these results indicated that Trp-P-1 and Try-P-2 acted at the nucleolar level by a blockade of pre-rRNA synthesis and at the extranucleolar by decreasing the ultrastructural RNP responsible for hnRNA synthesis.
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PMID:Ultrastructural and biochemical alterations induced by tryptophan pyrolysis products on rat hepatocytes in primary culture. I. Action on the transcriptional process. 683 20

Here we show that small RNAs homologous to short interspersed repetitive DNA sequences: ID, B1, B2--in rat cells and Alu in human cells are complexed with specific proteins to form small nuclear and cytoplasmic RNP particles (alpha RNP) with common properties. alpha-RNP differ from other ribonucleoproteins by composition and properties. alpha RNA molecules are apparently transcribed by RNA polymerase III. alpha-RNAs are capable of stable antisense hybridization with specific messenger RNAs. Expression of alpha-RNA is specifically regulated by gene regulatory factors. The data obtained support the suggestion that alpha-RNA may belong to the group of regulatory eukaryotic RNAs and that alpha-RNP might be involved in the coordinative control of the expression of the sets of genes with SINE-homologous sequences in regulatory regions.
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PMID:[A new class of RNP particles containing small RNA homologous to short dispersed DNA repetitive sequences]. 747 43

Ro ribonucleoprotein particles (Ro RNPs) are complexes of several proteins with a small RNA polymerase III-transcribed Ro RNA. Despite their relative abundance and evolutionary conservation no function has as yet been ascribed to these complexes. Also their subcellular distribution is still largely unknown as immunofluorescence studies concerning their localization have produced conflicting data. We have used cell enucleation to fractionate cells into cytoplasmic and nuclear fractions. Analysis of these fractions revealed an exclusively cytoplasmic localization for the Ro RNPs. The majority of the Ro RNAs are shown to be stably associated with all three known Ro RNP proteins. Although no Ro RNAs could be detected in the nuclear fraction, the Ro RNP-specific proteins were abundantly present. These nuclear non-Ro RNA-associated proteins are shown to be capable of binding Ro RNAs.
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PMID:Subcellular distribution of Ro ribonucleoprotein complexes and their constituents. 750 49

We have studied the distribution of poly(A)+ RNA in the mammalian cell nucleus and its transport through nuclear pores by fluorescence and electron microscopic in situ hybridization. Poly(A)+ RNA was detected in the nucleus as a speckled pattern which includes interchromatin granule clusters and perichromatin fibrils. When cells are fractionated by detergent and salt extraction as well as DNase I digestion, the majority of the nuclear poly(A)+ RNA was found to remain associated with the nonchromatin RNP-enriched fraction of the nucleus. After inhibition of RNA polymerase II transcription for 5-10 h, a stable population of poly(A)+ RNA remained in the nucleus and was reorganized into fewer and larger interchromatin granule clusters along with pre-mRNA splicing factors. This stable population of nuclear RNA may play an important role in nuclear function. Furthermore, we have observed that, in actively transcribing cells, the regions of poly(A)+ RNA which reached the nuclear pore complexes appeared as narrow concentrations of RNA suggesting a limited or directed pathway of movement. All of the observed nuclear pores contained poly(A)+ RNA staining suggesting that they are all capable of exporting RNA. In addition, we have directly visualized, for the first time in mammalian cells, the transport of poly(A)+ RNA through the nuclear pore complexes.
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PMID:In vivo analysis of the stability and transport of nuclear poly(A)+ RNA. 751 22

The organization of the U3, U8, and U13 small nucleolar ribonucleoproteins (snoRNPs) has been investigated in HeLa cells using antisense DNA and 2'-OMe RNA oligonucleotides. Oligomers corresponding to deoxynucleotides that target RNase H degradation of intact RNP particles were synthesized and used for fluorescence in situ hybridization. U3 and U13 are distributed throughout the nucleolus and colocalize with anti-fibrillarin antibodies. U8, however, is organized in discrete ring-like structures near the center of the nucleolus and surround bright punctate regions visualized with anti-RNA polymerase I and anti-UBF/NOR-90 antibodies. In decondensed nucleoli, a necklace of smaller ring-like structures of U8 RNA appear. A model for the recruitment of U8 (and presumably other processing factors) to the sites of rRNA transcription is discussed. Hybridization to mitotic cells showed that unlike pol I and NOR-90, U8 is dispersed into the cytoplasm during mitosis. The subnucleolar organization of U8 is consistent with its demonstrated participation in early intermediate steps in pre-rRNA processing. In contrast, the more dispersed intranucleolar distribution of U3 agrees with its putative involvement in both early and late steps of rRNA maturation. These studies illustrate the feasibility of mapping functional domains within the nucleolus by correlating the in vitro activities of small nuclear RNPs with their in situ locations.
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PMID:Organization of small nucleolar ribonucleoproteins (snoRNPs) by fluorescence in situ hybridization and immunocytochemistry. 753 31


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