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)

In this communication we identify and initially characterize two antagonistic activities in a Xenopus oocyte extract that can modulate the in vitro transcription of RNA polymerase III (pol III) genes (5 S RNA and tRNA genes). It was found that preincubation of an inhibitory factor, referred to here as fraction I, with fractions containing TFIIIB and TFIIIC/pol III leads to the loss of a reaction's ability to support transcription. This inactivation process, which required ATP or adenylyl-imidodiphosphate (but could not use ADP), occurred only in the absence of a 5 S RNA or tRNA gene containing plasmid. Under conditions in which transcription was lost, a loss in TFIIIC's ability to specifically bind to the tRNA gene was also observed. An activity found in the "A" fraction, which was first recognized for its ability to stimulate transcription, was found to inhibit and actually reverse the observed inactivation of transcription. This activity, referred to here as fraction A2, accomplished this reactivation regardless of whether the gene was present or not, but only when a hydrolyzable form of ATP was used in the inactivation process. Transcription in an inactivated reaction could also be restored by addition of fresh transcription factors. The data presented in this paper are consistent with a model in which fraction I and fraction A2 modulate transcription through the activation and inactivation of one or more positive transcription factors.
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PMID:The identification of two antagonistic activities in a Xenopus oocyte extract that can modulate the in vitro transcription of RNA polymerase III genes. 234 67

ADP-ribosylation is a posttranslational modification of proteins that has been related to many cellular events, such as DNA replication and repair, cell proliferation and differentiation. The present studies were performed in order to explore the possible relationship between nuclear protein ADP-ribosylation and RNA transcription in the thyroid gland. Inhibition of RNA transcription by alpha-amanitin and actinomycin D caused a decrease in ADP-ribosylation of 27 and 17%, respectively. Nicotinamide caused a dose-related inhibition of ADP-ribosylation, which was highest at 2 mM (around 90%). At this dose nicotinamide inhibited total RNA transcription by 46%, while the activity due to RNA polymerase II decreased by 50% and that related to RNA polymerases I+III dropped by 24%. These results suggest that inhibition of total nuclear protein ADP-ribosylation is accompanied by a parallel decrease in RNA transcription. Since our previous work has shown that TSH stimulates both nuclear ADP-ribosylation and RNA transcription it may be concluded that these activities follow parallel changes within the thyroid. When the same activities were assayed in normal human and in glands bearing follicular adenoma, RNA polymerase II was increased 4 fold in the latter group, without change in nuclear ADP-ribosylation. These results would suggest that a mechanism, distinct from ADP-ribosylation, may also be involved in the regulation of RNA transcription. This latter might be altered under this pathologic condition.
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PMID:Relationship between nuclear ADP-ribosylation and RNA transcription in calf and human thyroid. 244 64

A factor which eliminated nonspecific transcription of cloned rat rDNA was extensively purified from rat mammary adenocarcinoma ascites cells by successive fractionations on DEAE-Sephadex and heparin-Sepharose columns. The fractions containing RNA polymerase I (HS-B) and fractions eluting thereafter (HS-C) from the heparin-Sepharose column were pooled separately. Addition of HS-C to HS-B prevented random transcription of rDNA and yielded an accurate rDNA transcript with negligible non-specific transcription. The factor was essentially homogeneous and corresponded to Poly(ADP-ribose) polymerase with respect to molecular weight, dependence on DNA for its activity and its ability to undergo auto ADP-ribosylation. The total amount of protein in the transcription assay was approximately 2 micrograms, which indicates a high degree of purity of all the factors required for specific transcription of rDNA.
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PMID:Characterization of a factor that can prevent random transcription of cloned rDNA and its probable relationship to poly(ADP-ribose) polymerase. 298 93

The purified RNA polymerase complex of vesicular stomatitis virus required added thiols for maximal activity, whereas polymerase activity from whole disrupted virions did not. Maximal activity of the purified polymerase complex required greater than or equal to 1 mM added dithiothreitol. The polymerase was inactivated by N-ethylmaleimide (NEM) at 0 degree C, with k2 = 528 +/- 26 M-1 min-1. Activity was recovered by addition of L protein, but not N or NS, to the NEM-inactivated complex, indicating that the NEM-sensitive group was present on the L protein. Nucleoside triphosphates protected the enzyme against inactivation by N-ethylmaleimide. ATP was most effective, with KD = 0.58 +/- 0.07 mM, a value close to the Km of ATP reported previously for initiation of RNA synthesis. dATP was nearly as effective, and GTP was slightly less effective than ATP. Non-hydrolyzable analogs of ATP protected weakly, whereas ADP and pyrimidine triphosphates gave very poor, but still measurable, protection. The ATP binding site thus identified differs from the protein kinase-associated ATP binding site identified on L protein by Sanchez et al. (Sanchez, A., De, B.P., and Banerjee, A. K. (1985) J. Gen. Virol. 66, 1025-1036) in having a substantially lower affinity for ATP. Two putative ATP binding sites were identified in the L protein amino acid sequence, but none were found in the N or NS sequences.
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PMID:Inactivation of the RNA polymerase of vesicular stomatitis virus by N-ethylmaleimide and protection by nucleoside triphosphates. Evidence for a second ATP binding site on L protein. 303 24

Poly(ADP-ribose) synthetase is a chromatin-bound enzyme which synthesizes a protein-bound homopolymer of ADP-ribose utilizing NAD as a substrate. The characteristic nature of this enzyme is that it requires DNA for catalytic activity. The enzyme is rich in malignant tumor cells as well as in normal tissues where cell proliferation is very rapid. The enzyme has been purified to homogeneity from calf thymus, mouse testis and human placenta. The amino acid composition of these enzymes is very similar and a monoclonal antibody as well as antisera against the calf enzyme cross-reacts with mouse, chicken and human enzymes, suggesting that the antigenic structures of poly(ADP-ribose) synthetase are highly conserved in various animal cells. The native enzyme (Mr = 120K) is cleaved by limited proteolytic digestion into three different domains (Mr = 46K, 22K, 54K), the first containing the site for DNA binding, the second containing the site for automodification and the third containing the site for NAD binding. The DNA binding domain (Mr = 46K), like the native enzyme, has the ability to preferentially suppress nick induced random transcription initiation in a HeLa cell lysate, resulting in the production of run-off RNA initiated from the correct late promoter site on truncated DNA of adenovirus 2. The native enzyme poly(ADP-ribosyl)ates RNA polymerase and some other nuclear enzymes. These results, taken together, indicate that poly(ADP-ribose) synthetase plays a critical role in regulating gene expression in various eukaryotic cells.
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PMID:The domain structure and the function of poly(ADP-ribose) synthetase. 310 8

The bacteriophage T4 gene 55 protein endows Escherichia coli RNA polymerase core with the ability to recognize T4 late promoters. In these experiments, we show that T4 gene product (gp) 55, like the major E. coli RNA polymerase initiation subunit sigma 70, is released from elongating transcription complexes and is thus capable of cycling among molecules of RNA polymerase core. We also show that, paradoxically, sigma 70 is able to displace T4 gp55 from its site of binding to E. coli RNA polymerase core. After T4 infection, the core enzyme is ADP-ribosylated in each alpha subunit, and a T4-coded 11.4-kDa protein (rpbA) binds tightly to it; these modifications do not save gp55 from displacement by sigma 70. However, open T4 late promoter complexes, containing gp55, are resistant to attack by sigma 70.
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PMID:Interactions of the bacteriophage T4 gene 55 product with Escherichia coli RNA polymerase. Competition with Escherichia coli sigma 70 and release from late T4 transcription complexes following initiation. 330 6

DNA-dependent RNA polymerase B (II) from wheat germ was modified by incubation with 4-[N-(beta-hydroxyethyl)-N-methyl]benzaldehyde esters of AMP, ADP or ATP, followed by reduction with NaBH4. Reaction of the modified enzyme with [alpha-32P]UTP in the presence of various DNA templates led to a highly selective affinity labelling of the subunit with Mr 140 000 by covalently linked ApU. Labelling was inhibited by 1 microgram/ml alpha-amanitin.
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PMID:Highly selective affinity labelling of RNA polymerase B (II) from wheat germ. 370 95

Wheat germ RNA polymerase II is poly (ADP-ribosyl)ated in vitro by poly (ADP-ribose) synthetase purified from bovine thymus. RNA polymerase activity is decreased by 40% by the modification in conventional assays.
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PMID:Poly (ADP-ribosyl)ation of RNA polymerase II from wheat germ. 391 31

Two high-affinity oestrogen receptors have been identified in the chick oviduct with equilibrium dissociation constants (Kd) of 0.1 and 1 nM, differing in their binding kinetics, role in ovalbumin synthesis and independent regulation in vivo. The higher-affinity receptor (X) increases RNA polymerase II activity directly, whereas the low-affinity receptor (Y) seems to be necessary to confer specificity to transcription of oestrogen-dependent genes. Acute administration of progesterone to oestrogen-stimulated chicks results in preferential destruction of the nuclear Y receptor accompanied by interruption of ovalbumin gene transcription. Here we demonstrate that receptor Y exists in a non-oestradiol binding form (Ynb) which can be activated to the binding form in vitro by treatment with either ATP or ADP. Furthermore, dialysis of oviduct cytosol, which has no effect on the high-affinity receptor X, converts receptor Y to Ynb; receptor Y can then be recovered by treatment with ATP in the presence of Mg2+ and independently of Ca2+. This is the first report of the controlled interconversion between a non-steroid binding form of oestrogen receptor and active receptor in a tissue that contains two independently regulated oestrogen receptor types.
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PMID:Reversible activation of non-steroid binding oestrogen receptor. 399 Aug 3

When rat liver nuclear chromatin was sonicated in buffer containing 0.35 M (NH4)2SO4 to release the engaged RNA polymerases, a potent inhibitor was also released. This inhibitor elicited dramatic inhibition of RNA synthesis regardless of whether the free or engaged RNA polymerase was used. On further analysis, it became apparent that the site of inhibition was on the DNA template, not on the enzyme. This inhibitor could be extracted into 0.25 N HCl by the standard procedure for the isolation of histones. This acid-soluble inhibitor, showing typical histone band on gel, was RNase A and DNase I resistant, but was sensitive to both pronase and snake venom phosphodiesterase digestion, as well as to 0.1 N KOH hydrolysis. Furthermore, when [14C]adenine labeled poly-ADP-ribosylated histones were digested by snake venom phosphodiesterase, the release of radioactivity was in parallel to the loss of inhibitor activity. We conclude that the inhibitor substances are poly-ADP-ribosylated histones and propose that the poly-ADP-ribosylated histones rather than the histones are the natural suppressors of the gene.
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PMID:Poly-ADP-ribosylated histones: potent DNA suppressors. 404 88


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