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 Xenopus egg and embryo, throughout the transcriptionally inactive early cleavage period, were found to contain a store of approximately 8 X 10(8) molecules of the small nuclear RNA (snRNA) U1, sufficient for 4,000-8,000 nuclei. In addition, when transcription is activated at the twelfth cleavage (4,000 cell-stage), the snRNAs U1, U2, U4, U5, and U6 are major RNA polymerase II products. From the twelfth cleavage to gastrulation, U1 RNA increases sevenfold in 4 h, paralleling a similar increase in nuclear number. This level of snRNA transcription is much greater than that typical of somatic cells, implying a higher rate of U1 transcription or a greater number of U1 genes active in the embryo. The Xenopus egg also contains snRNP proteins, since it has the capacity to package exogenously added snRNA into immunoprecipitable snRNP particles, which resemble endogenous particles in both sedimentation coefficient and T1 RNase digestibility. SnRNP proteins may recognize conserved secondary structure of U1 snRNA since efficient packaging of both mouse and Drosophila U1 RNAs, differing 30% in sequence, occurs. The Xenopus egg and embryo can be used to pose a number of interesting questions about the transcription, assembly, and function of snRNA.
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PMID:Small nuclear RNA transcription and ribonucleoprotein assembly in early Xenopus development. 619 Aug 22

The difference boundary sedimentation velocity technique of Schachman and co-workers is demonstrated to be applicalbe to the measurement of binding constants (Kobsd) in the range 10(2)-10(5) M(-1) for the nonspecific interactions of proteins with DNA. The difference technique can reproducibly detect a 2% change in the sedimentation coefficient of the DNA upon binding ligands, corresponding to average extents of association as low as 10 molecules of protein (in the cases of Escherichia coli lac repressor and E. coli RNA polymerase) per molecule of bacteriophage T7 DNA. At these low binding densities, it is plausible to assume that the primary effect of ligand binding is on the buoyant mass of the complex and not on the frictional coefficient of the flexible DNA coil. Binding constants calculated by using this assumption agree well with literature values for the nonspecific interactions of RNase and lac repressor proteins with double-stranded DNA. Advantages of the method are that it is relatively rapid, requires the optical detection of the DNA only, and can be performed on small amounts of sample. The method appears useful for surveying (to an accuracy of +/-50% in Kobsd or +/-10% in log Kobsd) the effects of solution variables on Kobsd of protein-DNA interactions. Applications of the method to the nonspecific interactions of RNA polymerase core and holoenzymes with T7 DNA are discussed.
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PMID:Use of difference boundary sedimentation velocity to investigate nonspecific protein-nucleic acid interactions. 625 May 71

An endonuclease, which was originally identified for its RNA polymerase inhibitory activity, was isolated from rat liver endoplasmic reticulum. The enzyme yields on gel chromatography four active fractions of different molecular weights (Mr 5.3 X 10(4), 9 X 10(4), 1.55 X 10(5) and Sephacryl S-200 fraction at V0). Each fraction contains polypeptide chains which give a single band on sodium dodecylsulphate electrophoresis (Mr 5.4 X 10(4). This indicates that the enzyme is an oligomeric protein and each of its subunits exhibits the same or very similar molecular weights. Deoxyribonucleoside and ribonucleoside triphosphates can bind to the endoplasmic reticulum nuclease. Binding is enhanced in the presence of divalent cations particularly Mg2+. The enzyme exhibits mainly RNase activity but can also degrade denatured DNA and DNA . RNA hybrids which contain breaks in one of the two strands. Poly(A) and mainly poly(U) are most susceptible to its nucleolytic activity whereas poly(C) is completely resistant.
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PMID:Endoplasmic reticulum nuclease. Purification and specificity. 627 70

We have shown by T(1) oligonucleotide fingerprinting that the genome of mouse hepatitis virus strain A59 and its intracellular RNA 1 have identical fingerprints and that RNA 1 and the subgenomic RNAs 3, 6, and 7 contain common sequences. To localize the homologous region between the RNAs, we compared fingerprints of the 3' terminus of the genome with those of RNA 7. The genome was partially degraded with alkali, and polyadenylate-containing fragments were purified by oligodeoxythymidylate-cellulose chromatography. The fragments were size fractionated by agarose-urea gel electrophoresis, and two pools, x and z, containing 3'-derived fragments of the genome with apparent molecular weights of 0.1 x 10(6) to 0.14 x 10(6) and 0.6 x 10(6) to 0.8 x 10(6), respectively, were further analyzed by RNase T(1) oligonucleotide fingerprinting. Comparison of the fingerprints of RNAs 6 and 7 with those of pools x and z showed that these subgenomic RNAs extend inwards from the 3' terminus of the genome. The RNA fragments present in pool z were on average slightly larger than RNA 7 as confirmed by the presence in pool z of T(1) oligonucleotide spots specific for RNA 6 but not present in RNA 7. However, two large oligonucleotide spots derived from RNA 7, which were also present in RNAs 1, 3, and 6 and in the virion RNA, were not found in the T(1) oligonucleotide map of pool z. A possible explanation is that the two spots were derived from a leader sequence. The results of UV transcription mapping experiments (L. Jacobs, W. J. M. Spaan, M. C. Horzinek, and B. A. M. van der Zeijst, J. Virol. 39:401-406, 1981) excluded the possibility that such a leader sequence arises by splicing from a larger precursor molecule, but either a virus-specific RNA primer molecule for the synthesis of mRNAs or an RNA polymerase jumping mechanism could explain the presence of a leader sequence.
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PMID:Sequence relationships between the genome and the intracellular RNA species 1, 3, 6, and 7 of mouse hepatitis virus strain A59. 628 66

During the past two decades, the essentiality of zinc for man has been established. Deficiency of zinc in man due to nutritional factors and several diseased states has been recognized. High phytate content of cereal proteins decreases availability of zinc; thus the prevalence of zinc deficiency is likely to be high in a population subsisting mainly on cereal proteins. Alcoholism is known to cause hyperzincuria and thus may play a role in producing zinc deficiency in man. Malabsorption, cirrhosis of the liver, chronic renal disease and other chronically debilitating diseases may similarly induce zinc deficiency in human subjects. A severe deficiency of zinc has recently been recognized to occur in patients with sickle cell anemia and a beneficial effect of zinc therapy in such patients has been reported. Growth retardation, male hypogonadism, skin changes, poor appetite, mental lethargy and delayed wound healing are some of the manifestations of chronically zinc-deficient human subjects. Taste abnormalities, correctable with zinc supplementation, have been observed in uremic subjects. Recently, abnormal dark adaptation related to zinc deficiency in patients with cirrhosis of the liver and sickle cell disease has been reported. In severely zinc-deficient patients, dermatological manifestations, diarrhea, alopecia, mental disturbances and intercurrent infections predominate and if untreated the condition becomes fatal. Zinc deficiency is known to affect testicular functions adversely in man and animals. This effect of zinc is at the end organ level and it appears that zinc is essential for spermatogenesis and testosterone steroidogenesis. Zinc is involved in many biochemical functions. Several zinc metalloenzymes have been recognized in the past decade. Zinc is required for each step of cell cycle in microorganisms and is essential for DNA synthesis. Thymidine kinase, RNA polymerase, DNA-polymerase from various sources and RNA-dependent DNA polymerase from viruses have been shown to be zinc-dependent enzymes. Zinc also regulates the activity of RNase; thus the catabolism of RNA appears to be zinc-dependent. The effect of zinc on protein synthesis may be attributable to its vital role in nucleic acid metabolism. The activities of many zinc-dependent enzymes have been shown to be affected adversely in zinc-deficient tissues. Three enzymes, alkaline phosphatase, carboxypeptidase and thymidine kinase, appear to be most sensitive to zinc restriction in that their activities are affected adversely within three to six days of institution of a zinc-deficient diet to experimental animals.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Zinc deficiency in human subjects. 636 78

The protein compositions of purified metaphase chromosomes, nuclei and their residual scaffold and matrix structures, are reported. The protein pattern of nuclei on sodium dodecyl sulphate/polyacrylamide gels is considerably more complex and rich in non-histone proteins than that of chromosomes. Nuclei contain about three to four times more non-histone proteins relative to their histones than chromosomes. Besides the protein components of the peripheral lamina, several protein bands are specific or at least highly enriched in nuclei. Conversely, two proteins X0 (33 X 10(3) Mr) and X1 (37 X 10(3) Mr) are highly enriched in the pattern of metaphase chromosomes. We have compared morphologically the previously defined nuclear matrices type I and II. The type I nuclear matrix is composed of the known lamina proteins, which form the peripheral lamina structure, and a complex series of proteins that form the internal network of the matrix as observed by electron microscopy. This internal network is stabilized similarly to the metaphase scaffolding by metalloprotein interaction. Both the scaffolding and the internal network of the matrix dissociate if thiols or certain metal chelators are used in the extraction buffer. Under these conditions the resulting nuclear structure, called matrix type II, appears empty in the electron microscope, with the exception of some residual nucleolar material. This latter material can be extracted from the internal network by exhaustive treatment of the nuclei with RNase before extraction with high salt. Immunoblotting and activity studies show RNA polymerase II to be tightly bound to the type I, but not to the type II matrix, or to the scaffolding structure. No polymerase II enzyme was detected in isolated metaphase chromosomes. Another nuclear enzyme, poly(ADP-ribose) polymerase is not bound to either of the residual nuclear matrices or to the scaffolding structures. The association of RNA polymerase with the internal network of the nuclear matrix is consistent with the idea that transcription occurs in close association with this structure.
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PMID:Interphase nuclear matrix and metaphase scaffolding structures. 639 68

When rat liver nuclei were digested with nuclease, we found that the chromatin-bound RNA polymerase II was liberated as two distinct complexes, peak 1 and peak 2, which seemed to reflect different functional states in cell nuclei. We further examined their occurrence in nuclear digests of various tissues of rats and the following results were obtained. Upon digestion with micrococcal nuclease of nuclei from brain, spleen, testis and kidney, chromatin-bound RNA polymerase II was liberated as two distinct forms which sedimented differently in a sucrose density gradient. The sedimentation rate of peak 1 varied depending on the tissue nuclei examined. After high salt or RNase treatment of the nuclear digests, peak 1 from liver, brain, spleen and testis nuclei showed the same sedimentation rate as did kidney peak 1, the rate for which remained unchanged by these treatments. The results suggested that peak 1 complexes from various tissue nuclei had basically the same structural organization, and we confirmed this by electrophoretic studies on RNase-treated liver and kidney nuclear digests. Peak 2 from various tissue nuclei exhibited identical sedimentation rates. Thus, the chromatin-bound RNA polymerase II seems to exist commonly in two distinct states in cell nuclei of rats.
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PMID:Two species of chromatin-RNA polymerase II complex are commonly present in nuclei of various tissues of rats. 652 8

DNA-dependent RNA polymerase activity has been studied in isolated nuclei from canine mammary tumours. Initial experiments showed high levels of RNase activity in this tissue; accordingly, routine assays were terminated before loss of acid-precipitable radioactivity was evident. RNA polymerase A and B activity in isolated nuclei were shown to be increased by addition of receptor-containing cytosol previously incubated with oestradiol-17 beta, dihydrotestosterone or R5020. Where no receptor was present, as measured by saturation binding assays and sucrose density gradient analysis, there was no corresponding increase in polymerase activity. The steroid antagonists tamoxifen and cyproterone did not elicit any response even when their corresponding steroids produced a 1- to 2-fold stimulation of polymerase activity. Steroid-induced effects proved to be dose-dependent, with half maximal responses for oestradiol-17 beta 8 X 10(-8)M, R5020 2 X 10(-6)M and dihydrotestosterone 9 X 10(-6)M.
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PMID:Cytoplasmic steroid effects on nuclear RNA polymerase activity in canine mammary carcinomas. 668 76

An RNA polymerase activity was found to be associated with the infectious drosophila X virus particles extracted from infected flies. The rate of synthesis was at first linear as a function of time, and then a plateau was reached. During the linear phase of the synthesis, the template and product were associated as replicative intermediates which were larger than the double-stranded RNA of the drosophila X virus genome, but the final product of the reaction was indistinguishable from the RNA genome with respect to its density, sedimentation coefficient, electrophoretic mobility, and RNase resistance. The results indicated that both strands of the genomic RNA were copied. The implications of these findings with regard to other virion polymerases are discussed.
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PMID:Drosophila X virus RNA polymerase: tentative model for in vitro replication of the double-stranded virion RNA. 677 7

An Alu-type dispersed repeat previously identified in a cloned fragment of Chinese hamster DNA [Haynes, S. R., Toomey, T. P., Leinwand, L. & Jelinek, W. R. (1981) Mol. Cell. Biol. 1, 573-583] serves as a template for cell-free transcription of discrete low molecular weight RNAs by RNA polymerase III [RNA nucleotidyltransferase (DNA-directed), EC 2.7.7.6]. A class of analogous RNAs has been isolated from growing Chinese hamster cells by hybridization of total low molecular weight nuclear RNAs to the cloned DNA fragment from which cell-free transcription occurs. Two-dimensional analysis of RNase digestion products of these RNAs suggests that they are transcribed from multiple members of the Alu-type dispersed repeat family.
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PMID:Low molecular weight RNAs transcribed in vitro by RNA polymerase III from Alu-type dispersed repeats in Chinese hamster DNA are also found in vivo. 679 57


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