共查询到20条相似文献，搜索用时 273 毫秒
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RNA polymerase IV directs silencing of endogenous DNA 总被引：1，自引：0，他引：1
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Yeast RNA polymerase II genes: isolation with antibody probes 总被引：161，自引：0，他引：161
Genes encoding yeast RNA polymerase II subunits were cloned. Efficient isolation of these genes was accomplished by probing a phage lambda gt11 recombinant DNA expression library with polyvalent antibodies directed against purified yeast RNA polymerase II. The identity of genes that specify the largest RNA polymerase II subunits, the 220,000- and 150,000-dalton polypeptides, was confirmed by competitive radioimmune assay. Both of these genes exist in single copy in the yeast Saccharomyces cerevisiae. 相似文献
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A persistent untranslated sequence within bacteriophage T4 DNA topoisomerase gene 60 总被引：30，自引：0，他引：30
W M Huang S Z Ao S Casjens R Orlandi R Zeikus R Weiss D Winge M Fang 《Science (New York, N.Y.)》1988,239(4843):1005-1012
A 50-nucleotide untranslated region is shown to be present within the coding sequence of Escherichia coli bacteriophage T4 gene 60, which encodes one of the subunits for its type II DNA topoisomerase. This interruption is part of the transcribed messenger RNA and appears not to be removed before translation. Thus, the usual colinearity between messenger RNA and the encoded protein sequence apparently does not exist in this case. The interruption is bracketed by a direct repeat of five base pairs. A mechanism is proposed in which folding of the untranslated region brings together codons separated by the interruption so that the elongating ribosome may skip the 50 nucleotides during translation. The alternative possibility, that the protein is efficiently translated from a very minor and undetectable form of processed messenger RNA, seems unlikely, but has not been completely ruled out. 相似文献
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Visualizing the higher order folding of a catalytic RNA molecule 总被引：26，自引：0，他引：26
The higher order folding process of the catalytic RNA derived from the self-splicing intron of Tetrahymena thermophila was monitored with the use of Fe(II)-EDTA-induced free radical chemistry. The overall tertiary structure of the RNA molecule forms cooperatively with the uptake of at least three magnesium ions. Local folding transitions display different metal ion dependencies, suggesting that the RNA tertiary structure assembles through a specific folding intermediate before the catalytic core is formed. Enzymatic activity, assayed with an RNA substrate that is complementary to the catalytic RNA active site, coincides with the cooperative structural transition. The higher order RNA foldings produced by Mg(II), Ca(II), and Sr(II) are similar; however, only the Mg(II)-stabilized RNA is catalytically active. Thus, these results directly demonstrate that divalent metal ions participate in general folding of the ribozyme tertiary structure, and further indicate a more specific involvement of Mg(II) in catalysis. 相似文献
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Secretion of activin by interstitial cells in the testis 总被引：3，自引：0，他引：3
Activin, a dimer formed by the beta subunits of inhibin, has an effect that is opposite to that of inhibin in a number of biological systems. Which cell types secrete activin in vivo is not known. TM3 cells, a Leydig-derived cell line, contained messenger RNAs that hybridized with human beta A and beta B complementary DNA probes and were similar in size to the porcine messenger RNA for the beta subunits of inhibin. No hybridization to the inhibin alpha subunit was detectable in the TM3 cells. Conditioned medium from TM3 cells and from primary cultures of rat and porcine interstitial cells stimulated the release of follicle-stimulating hormone in a pituitary cell culture assay. It is likely that, in the testis, the Leydig cells secrete activin and the Sertoli cells produce inhibin, or a combination of both. 相似文献
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Binding of benzo[a]pyrene 7,8-diol-9,10-epoxides to DNA, RNA, and protein of mouse skin occurs with high stereoselectivity 总被引：7，自引：0，他引：7
M Koreeda P D Moore P G Wislocki W Levin H Yagi D M Jerina 《Science (New York, N.Y.)》1978,199(4330):778-781
The formation, stereostructure, and cellular reactions of the 7,8-diol-9,10-epoxide metabolites of the carcinogen benzo[a]pyrene have been examined after topical application of benzo[a]pyrene to the skin of mice. In this known target tissue, polymer adducts from diastereomeric diol epoxides, (+)-(7S, 8R, 9R, 10R) and (+)-(7R, 8S, 9R, 10R), were formed stereospecifically from their corresponding 7,8-dihydrodiols. Both diol epoxides bind with proteins, RNA, and DNA in vivo. For the nucleic acids, binding occurs preferentially at the 2-amino group of guanine in cellular RNA and DNA in vivo. Methods for establishing the structure of the cellular adducts as well as the possible biological implications of their formation are discussed. 相似文献
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alpha-Difluoromethylornithine-induced polyamine depletion of 9L tumor cells modifies drug-induced DNA cross-link formation 总被引：1，自引：0，他引：1
Depletion of intracellular levels of polyamines, which are believed to have a role in the intranuclear stabilization of DNA, alters the cytotoxicity of 1,3-bis(2-chloroethyl)-1-nitrosourea and cis-diamminedichloroplatinum II in 9L rat brain tumor cells. Alkaline elution techniques were used to show that polyamine depletion alters the number of DNA cross-links formed by these cytotoxic agents. 相似文献
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小麦高分子量麦谷蛋白亚基组成与面包烘烤品质关系的研究 总被引：12，自引：0，他引：12
研究高分子量麦谷蛋白亚基组成与小麦品质性状(SDS沉降值、比沉降值)的关系.结果表明,Glu-Al、Glu-Bl和Glu-Dl位点控制的亚基等位变异与品质性状密切相关.在Glu-Al位点控制的3种亚基等位变异类型中,对品质的效应以1=2*＞N(缺失);在Glu-Bl位点控制的4种亚基等位变异类型中,对品质的效应以17+18=7+8＞7+9=6+8;在Glu-Dl位点控制的2种亚基等位变异类型中,对品质的效应以5+10＞2+12.具亚基1或2*,17+18或7+8,5+10组合类型的小麦品种可望有较好的烘烤品质. 相似文献
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The glucocorticoid receptor protein binds to transfer RNA 总被引：6，自引：0，他引：6