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 relationship between the in vitro phosphorylation of vesicular stomatitis virus (VSV) proteins and virion uncoating was examined. Activation of the VSV virion kinase with low concentrations of melittin, the active peptide component of bee venom, in the presence of gamma-[32P] ATP resulted in the phosphorylation of virion proteins. Following the in vitro phosphorylation of VSV proteins in the presence of melittin and deoxyadenosine triphosphate, the virion envelope was disrupted based on the accessibility of the internal ribonucleoprotein core (RNP) to the heavy metal stain, uranyl acetate, as determined by electron microscopic observation. The RNP structure was not observed in unphosphorylated virions treated with melittin and uranyl acetate. Phosphorylated virions treated with uranyl acetate subsequently lost the capacity for transcription whereas unphosphorylated virions treated with the stain retained transcriptase activity. These observations suggest that phosphorylation of VSV proteins may contribute to virion uncoating by disrupting the virus envelope.
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PMID:Phosphorylation of vesicular stomatitis virus proteins as a possible contributing factor in virion uncoating. 617 11

Small ribonucleic acid (RNA)-protein complexes precipitated by anti-Ro and anti-La antibodies from lupus patients have been examined with emphasis on their RNA components. In both ribonucleoprotein (RNP) classes, the numbers of different RNA molecules and their sequences vary between mouse and human cells. The complex mixtures of La RNAs include two previously sequenced 4.5S RNAs from mouse cells and 5S ribosomal RNA-like molecules from both mouse and human cells. All Ro and La RNAs possess 5-triphosphates. Some La RNAs have internal modifications typical of transfer RNAs. The Ro RNPs are quite stable and are localized by immunofluorescence in the cell cytoplasm, whereas the majority of the La RNPs turn over rapidly and reside in the nucleus. Despite these differences, reconstitution experiments show that the Ro particles carry the La as well as the Ro determinant. Studies using a nuclear transcription system demonstrate that most of the La RNAs are synthesized by RNA polymerase III. The possibility that the La protein(s) functions in the transcription or maturation of all RNA polymerase III transcripts is discussed.
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PMID:Ro small cytoplasmic ribonucleoproteins are a subclass of La ribonucleoproteins: further characterization of the Ro and La small ribonucleoproteins from uninfected mammalian cells. 618 Feb 98

Classical electron-microscopic techniques (enzymic digestion, EDTA regressive staining) allied with autoradiographic studies after [3H]uridine incorporation or after RNA synthesis initiated by an exogeneous RNA polymerase in the presence of tritiated GTP, enabled us to describe the fine structure and activity of the nucleolus in an established Drosophila cell line. This nucleolus is composed of a large central multilobed core containing proteins, RNA molecules and a DNA-containing component. This core is surrounded by and connected to large clumps of dense fibrillar nucleolus-associated chromatin, which are intermingled with fibrillogranular ramifications extending from the core towards the nuclear envelope. These ramifications are covered by granules of ribosomal ribonucleoprotein. As shown by EDTA regressive staining the nucleolar core contains a ribonucleoprotein network, which unravels and ramifies within a fibrous matrix. RNA synthesis takes place at the level of this network in the internal part of the core. The molecules synthesized are associated with proteins and are exported out of the core in the form of granules. Although it is composed of the same constituents as other nucleoli, the nucleolus of Drosophila cells seems to be less organized, in that it never displays fibrillar centres, which have been referred to as the nucleolar counterparts of the nucleolus-organizers in a wide variety of organisms.
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PMID:Nucleolar organizer structure and activity in a nucleolus without fibrillar centres: the nucleolus in an established Drosophila cell line. 618 16

We have studied the ultrastructure of the Balbiani ring genes in Chironomus tentans during treatment with the RNA synthesis inhibitor DRB (5,6-dichloro-1-beta-D-ribofuranosyl-benzimidazole). This nucleoside analogue blocks transcription at or near the initiation site but does not interfere with the elongation and termination processes. In the ordinary active state the Balbiani ring genes display a 5 nm chromosome fiber, carrying densely distributed, growing ribonucleoprotein particles (Andersson et al., 1980). When the transcriptional activity declines, a 10 nm fiber can be observed between sparsely distributed RNA polymerases. Furthermore, after passage of the last RNA polymerase the 10 nm fiber can be seen as well as its gradual packing into a 25 nm thick fiber. Thus, the active chromosome fiber is rapidly packed into higher order structures when the fiber is not directly involved in transcription. The formation of the thick fiber does not require that the gene along its entire length is devoid of active RNA polymerases. The thick fiber can again be mobilized for transcription, since in reversion experiments the BR genes appear as ordinary active genes with an extended nucleofilament and densely packed nascent transcription products. The dynamic behaviour of the chromosome fiber during transcription is discussed as well as the packing and unpacking of a gene into higher order structures.
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PMID:Rapid reformation of the thick chromosome fiber upon completion of RNA synthesis at the Balbiani ring genes in Chironomus tentans. 618 41

Soluble transcriptase containing the L and the NS proteins was isolated from purified vesicular stomatitis virus and its binding with the template ribonucleoprotein containing the N protein-RNA complex was studied with respect to its ability to initiate and synthesize RNA in vitro. By using u.v.-irradiated template reconstituted with soluble transcriptase, it was shown that the synthesis of leader RNA and other small initiated mRNA sequences continued while full-length mRNA synthesis decreased by 90%. In the presence of ATP and CTP, the reconstituted complex synthesized polyphosphorylated oligonucleotides which include AC, AAC and AACA which represent 5'-terminal sequences transcribed from the leader template and genes coding for mRNAs. In the presence of arabinosyl ATP, an inhibitor of RNA synthesis in vitro, the synthesis of leader RNA was found to be inhibited considerably more than other small initiated mRNA sequences. Reconstitution of RNA synthesis with soluble transcriptase and template in the presence of viral matrix (M) protein at low ionic condition resulted in virtual cessation of leader RNA synthesis, although the synthesis of small initiated N mRNA, 11 to 14 bases, continued. These results suggest that transcriptase can bind at multiple sites on the genome template and initiate RNA chains.
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PMID:Interaction of L and NS proteins of vesicular stomatitis virus with its template ribonucleoprotein during RNA synthesis in vitro. 619 59

Anti-La sera from patients with autoimmune disorders precipitate a set of nuclear and cytoplasmic small RNA-protein complexes. Up to now, it has been thought that the La antigen is associated only with RNAs transcribed by RNA polymerase III, including precursors of tRNA and 5 S ribosomal RNA. Here we report that anti-La sera also react with ribonucleoprotein particles containing small nuclear RNA U1, which is transcribed by RNA polymerase II. Anti-La sera from 12 out of 12 patients tested were found to precipitate U1 RNA-protein complexes from HeLa cell nuclear extracts, under conditions where nonimmune sera do not. Ribonucleoprotein particles containing a second small nuclear RNA, U2, do not react appreciably with anti-La sera although they are present in HeLa cell nuclei at the same concentration as U1 RNA. Anti-La sera also react with U1 RNA-protein complexes in mouse and frog cells, but not in Drosophila or Chironomus, two organisms which lack the La antigen. Hybridization of cloned U1 DNA with anti-La-reactive RNA from HeLa cell nuclear extracts reveals mature U1 RNA, whereas anti-La-reactive cytoplasmic RNA contains a series of hybridizing bands that represent molecules 1-7 nucleotides longer than U1 and which may include precursors of nuclear U1 RNA (Madore, S. J., Wieben, E. D., and Pederson, T. (1984) J. Cell Biol., 188-192). Pulse-chase experiments suggest that the association of La antigenicity with these cytoplasmic U1 RNA molecules is transient. These results are discussed in relation to the presence of uridylate-rich sequences in the 3' termini of U1 RNA precursors and mature U1 RNA, which are similar to La antigen binding sites in several RNAs transcribed by RNA polymerase III.
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PMID:Eukaryotic small ribonucleoproteins. Anti-La human autoantibodies react with U1 RNA-protein complexes. 622 41

RNA polymerase III transcription can be inhibited in vitro by two sera from patients with autoimmune diseases. The first serum, designated anti-SS-B (or La), has antibodies directed against a 50,000 dalton polypeptide that is part of a larger ribonucleoprotein complex. The second serum, designated anti-SpNo, recognizes a target antigen polypeptide of greater than 100,000 daltons as well as the SS-B antigen. Both sera selectively remove required transcription factors from the transcription extract, and inhibition can be rescued by the addition of a HeLa S100 extract to the depleted transcription system. The HeLa S100 extract was sequentially fractionated by ion-exchange chromatography on DEAE-cellulose and phosphocellulose. The high salt eluate from the latter column was also able to rescue the anti-SS-B inhibition as was the immunoaffinity-purified SS-B ribonucleoprotein complex isolated from HeLa, Xenopus or rabbit thymus. Immunoblots of the active fractions indicated that all contained the SS-B immunoreactive polypeptide, but probes of replica filters for DNA-binding suggested that the transcription factor is not the SS-B antigen but a 64,000 dalton polypeptide component of the antigen ribonucleoprotein complex. SS-B is itself an RNA-binding protein and could be shown to bind nascent 5S RNA transcripts in vitro. Differential ammonium sulfate precipitation and DNA cellulose chromatography has confirmed that a group of 64-68 K dalton polypeptides are components of the SS-B ribonucleoprotein complex associated with transcription factor activity.
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PMID:Association of an RNA polymerase III transcription factor with a ribonucleoprotein complex recognized by autoimmune sera. 623 2

The effect of proteins soluble in acidic chloroform-methanol (ACMS proteins) on the transcriptase activity of virus ribonucleoproteins (RNPs) in vitro has been studied. Experiments with ACMS membrane (M) proteins from type A and B orthomyxoviruses, as well as from vesicular stomatitis virus, showed that inhibition of the viral RNP transcriptase activity occurred when they interacted with M proteins isolated from viruses of a different serotype, or even of a different family. The presence of ACMS proteins capable of inhibiting the transcriptase activity of orthomyxovirus RNP in vitro was also detected in human blood plasma and among proteins produced by human leukocytes. Determination of the minimum concentration of M protein inhibiting the RNP transcriptase activity, and analysis of the fowl plague virus M protein-RNP complex formed in the in vitro system, showed that the M protein was capable of inhibiting RNP transcriptase activity at a M:RNP ratio of 0.1 to 0.2:1.
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PMID:In vitro inhibition of negative strand virus transcriptase activity by proteins soluble in acidic chloroform-methanol. 630 Feb 85

Transcription of the Bal I E restriction fragment of adenovirus DNA by RNA polymerase II in a HeLa cell extract produces a RNA transcript 1,712 nucleotides in length. This transcript contains the first two elements of the tripartite leader that, in vivo, is spliced onto the late mRNAs. We have found that this adenovirus 2 transcript forms a specific ribonucleoprotein complex (RNP) in this in vitro system. The RNP particle sediments in sucrose gradients as a monodisperse peak at 50 S and has a buoyant density of 1.34 g/cm3 in Cs2SO4, indicating the same 4:1 protein/RNA composition as native nuclear RNPs that contain pre-mRNA sequences (hnRNP). Moreover, the in vitro-assembled RNP is resistant to concentrations of NaCl that are known to dissociate nonspecific RNA-protein complexes. The adenovirus 2 transcript is precipitated by a monoclonal antibody for hnRNP core proteins. In addition, RNA-protein crosslinking of [alpha-32P]UTP-labeled transcript/RNP complexes reveals that the major proteins in contact with the RNA are the Mr 32,500-41,500 species known to be associated with hnRNA in vivo. These results demonstrate the in vitro assembly of a specific RNA polymerase II transcript into RNP. Moreover, because the 1,712-nucleotide adenovirus 2 transcript lacks poly(A) addition sites and because the leader sequences are not spliced appreciably in this in vitro system, it follows that RNP formation requires neither polyadenylylation nor splicing, nor is it sufficient to cause the latter.
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PMID:In vitro assembly of a pre-messenger ribonucleoprotein. 630 13

The heart contains many cell types; mechanical work is done by cardiomyocytes which do not divide but are terminally differentiated and capable of continuous protein synthesis and degradation. The steps in protein synthesis are (1) transport of amino acids into heart cells by a variety of cell-membrane carriers, (2) ATP-dependent activation of the amino acids by specific enzymes, forming aminoacyl-transfer RNA molecules, (3) initiation of protein synthesis on ribosomes to which messenger-RNA molecules are bound at the initiation 'code word', (4) elongation of the polypeptide chains by the repetitive operation of a ribosomal enzyme acting on incoming aminoacyl-transfer RNAs selected by their ability to bind to the messenger-RNA code words in place at any one time, and (5) completion of chain growth when the appropriate termination code word appears in the messenger RNA on the ribosome. Certain genes are available in differentiated heart cells for transcription by RNA polymerase into pre-messenger RNA molecules. These RNA molecules are chemically modified, complexed with proteins and shortened by means of specific excisions before they leave the nuclei as messenger-ribonucleoprotein complexes which can be used for protein synthesis. Regulation of protein synthesis involves both 'quantity' and 'quality' control and is exerted mainly, but not exclusively, at the two levels of initiation, namely that of RNA synthesis in the nucleus, and protein synthesis in the cytoplasm. Protein degradation to the level of amino acids is a process which probably requires disassembly of protein complexes or organelles, and is catalyzed by proteinases present in the cytoplasm or by others occurring in lysosomes, or possibly by both. Basal degradation occurs continuously, and may be supplemented by a separate process, called autophagy, which is under hormonal or nutritional control. The complex processes of biosynthesis and degradation are finely balanced and do not interfere with function despite their occurrence at a rate which means that most of the cardiac protein is replaced every 7 to 14 days. Nutritional and hormonal factors, and especially workload, are determinants that influence the 'set' of the protein turnover mechanism and therefore the size of the organ as a whole.
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PMID:Protein metabolism of the heart. 636 40


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