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)

Reverse transcriptase from avian retrovirus has a physically associated DNA endonuclease with novel substrate and cofactor requirements. A similar endonuclease activity copurifies with pp32, a protein from viral cores that has been identified with the non-alpha region of the beta subunit of reverse transcriptase. Several temperature-sensitive mutants of avian retrovirus with thermolabile DNA polymerase were tested for thermal sensitivity of their DNA endonuclease activity. Two pol mutants of Rous sarcoma virus, ts335 and ts337, had thermolabile DNA endonuclease; a temperature-resistant revertant of ts335 had a heat-stable DNA endonuclease. DNA endonuclease is therefore a product of the pol gene and an integral part of the reverse transcriptase. A second class of pol mutants, typified by ts568 and ts553, had thermolabile DNA polymerase, but heat-stable DNA endonuclease.
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PMID:Virus-coded DNA endonuclease from avian retrovirus. 616 35

1. The hypertrophic rat kidney after unilateral nephrectomy showed a time-dependent increase in the RNA/DNA ratio. This was associated with the increased rate of alpha-amanitin-insensitive RNA synthesis in isolated nuclei. 2. The increased activity of solubilized RNA polymerase was due to polymerase I, II and III as judged from the DEAE-Sephadex chromatography. 3. Chromatin DNA from hypertrophic kidneys was more susceptible to DNAase I than DNA from control kidneys.
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PMID:Effect of unilateral nephrectomy on the RNA synthesis in hypertrophic rat kidney. 616 51

One of the factors regulating the accessibility of specific DNA sequences to endonuclease nicking during meiosis is a group of small nuclear RNA molecules, 125 nucleotides in length and transcribed by RNA polymerase III. These molecules (referred to as PsnRNA) are synthesized during meiotic prophase, when chromosomes are undergoing homologous pairing or are already paired. Accessibility to the meiotically active DNA sequences (P DNA) depends on an as-yet-undefined alteration in chromatin structure. PsnRNA is a critical factor in the alteration; it cannot be replaced by other forms of RNA. The specificity of the chromatin sites altered by PsnRNA appears to be a function of sequence complementarity between it and P DNA. Under in vivo conditions the effective action of PsnRNA depends on homologous chromosome pairing. Chromatin sites housing P-DNA sequences in nuclei isolated from cells lacking homologous pairing are not affected by meiotic endonuclease or DNAse II. Accessibility to these sites can be effected by incubation of the nuclei with PsnRNA, but only if the nuclei are from zygotene-pachytene cells. Analyses of pachytene nuclei preincubated with PsnRNA indicate that PsnRNA renders chromatin accessible to at least two endonucleases, meiotic endonuclease and DNAase II, and that it also limits such accessibility to regions housing the complementary P-DNA sequences.
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PMID:Small nuclear RNA molecules that regulate nuclease accessibility in specific chromatin regions of meiotic cells. 617 41

Rat-liver nucleoli (10-15 micrograms DNA) were digested with either 0.6 or 3 units of DNase I for various times (up to 1 h). RNA synthesis was then measured in the absence or presence of 3 units of Escherichia coli RNA polymerase. It was found that the nucleolar chromatin supporting the endogenous engaged RNA polymerase I transcription was completely destroyed in 3 min with either concentration of DNase I. The nucleolar chromatin template transcribed by E. coli RNA polymerase retained 50% of its original capacity even 60 min after 3 units of DNase I digestion. When hybridization experiments were conducted, it was found that the DNAs derived from both levels of DNase-I-digested nucleoli were incapable of forming hybrids with the labelled nucleolar RNA synthesized by the engaged RNA polymerase I from the untreated nucleoli. Since the engaged RNA polymerase I transcribes only the physiologically active genes of the nucleolar chromatin, and the RNA transcripts represent active gene product, these data suggest that DNase I digestion has completely destroyed the active genes of the nucleolar chromatin, and E. coli RNA polymerase is able to transcribe the inactive nucleolar chromatin template.
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PMID:Evidence for the transcription os physiologically inactive rat-liver nucleolar chromatin by Escherichia coli RNA polymerase. 617 57

Cardiac hypertrophy in spontaneously hypertensive rats is associated with increased nuclear RNA polymerase activity. In order to explore mechanisms facilitating the interaction of the enzyme with its endogenous template, we compared the structure of nuclear chromatin from myocytes of 20-week-old spontaneously hypertensive rats and normotensive Wistar-Kyoto controls. Enhanced RNA synthesis in hypertensive rats was accompanied by increased susceptibility to digestion by deoxyribonuclease I. Nick translation of nuclei also resulted in higher nucleotide incorporation in hypertensive rats. Salt-extraction abolished the differences in deoxyribonuclease I sensitivity between the two animal groups. Reconstitution with either 0.35 M NaCl-extract or high mobility group (HMG) non-histone proteins restored digestion susceptibility but did not equalize SHR and WKY cells. SDS-polyacrylamide gel electrophoresis of 0.35 M NaCl-extracts and supernatants from deoxyribonuclease I digestion revealed the presence of HMG proteins which were preferentially released in hypertensive rats. There was a small but statistically significant increase in nuclear HMG protein content in hypertensive rats (0.12 +/- 0.02 mg/mg DNA vs. 0.09 +/- 0.02 mg/mg DNA in Wistar-Kyotos, P less than 0.05) but no difference in their electrophoretic appearance. These results indicate that chromatin structure is altered in the hypertrophied myocardium with resultant increase in deoxyribonuclease I susceptibility. This increase appears to be partly dependent on the high-mobility group non-histone proteins.
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PMID:Enhanced myocardial RNA synthesis in spontaneously hypertensive rats possible role of high-mobility group non-histone proteins. 617 42

An in vitro culture system for the proliferation of IgG-forming plasma cells from mouse bone marrow cultures has previously been described. The present study attempts to elucidate the mode of action of thymic RNA in these cultures. Autoradiography after using radiolabeled thymic RNA showed that radioactive material was mainly incorporated into the nuclei of IgG-forming plasma cells. No radiolabeled thymic RNA was incorporated into the cells except immunoblasts. The incorporated thymic RNA was acid insoluble and digested by RNase, but resistant to DNase and pronase. Radioactivity in the nucleotide pool after the cells were cultured with radiolabeled thymic RNA was negligible, indicating that reutilization of degraded RNA did not occur in the nuclei of the plasma cells. Moreover, the incorporation of radiolabeled thymic RNA by the cells was not prevented by excess unlabeled nucleosides. Escherichia coli transfer RNA, L-cell RNA and synthetic polynucleotide poly(A-U) were incorporated but were distributed in a different manner in the cells. A derivative of rifampicin, 2'5'-dimethyl N(4') benzyl-N(4')[desmethyl]rifampicin (AF/ABDMP), a possible inhibitor of RNA-dependent DNA polymerases, suppressed both the incorporation of thymic RNA and the differentiation of immunoblasts. AF/ABDMP suppressed DNA synthesis by bone marrow cultures to the same level as those pretreated with anti-mouse B-cell antibodies and complement. DNA dependent RNA polymerase activity was observed in the supernatant of bone marrow cultures stimulated by normal syngeneic thymic RNA and human gammaglobulin as antigen. These results imply a possible relationship between B-cell differentiation and RNA-dependent DNA polymerases.
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PMID:Intranuclear incorporation of thymic low molecular weight RNA by murine bone marrow immunoblasts and inhibition of plasma cell formation by a derivative of rifampicin. 617 4

Employing enzymatic reactions containing reverse transcriptase and appropriately defined substrates, we have demonstrated that the tRNATrp primer molecule required for the initiation of DNA synthesis is cleaved from viral DNA by an enzymatic activity associated with the reverse transcriptase molecule. Since the alpha subunit of reverse transcriptase facilitates release of the tRNATrp primer from viral DNA and this activity is inhibited by a known inhibitor of reverse-transcriptase-associated RNAase H, it appears that the RNAase H activity, rather than the DNA endonuclease activity, is involved in this reaction. The cleavage site for RNAase H-mediated removal of the tRNATrp primer from viral DNA is located at or near the tRNATrp-viral DNA junction, and transcription of most, if not all, of the tRNATrp-binding site into (+) polarity DNA occurs before RNAase-H-mediated cleavage takes place. These studies indicate that an additional function can be ascribed to the reverse-transcriptase-associated RNAase H activity, which in this instance acts like an endonuclease, not requiring the unblocked termini of an RNA-DNA hybrid molecule for its activity.
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PMID:Mechanism of release of the avian rotavirus tRNATrp primer molecule from viral DNA by ribonuclease H during reverse transcription. 618 6

The rate of in vivo transcription from the E. coli tRNA and rRNA promoters depends on both cellular growth rate and aminoacid availability. To investigate the molecular mechanisms involved we determined the extent of interaction of RNA polymerase with the promoter of the tyrT stable RNA gene. We show that the enzyme can protect from DNAase I digestion a region of at least 85 bp of the wild-type tyrT promoter and only approximately 62 bp of the lacUV5 mRNA promoter, the protected region extending on the antisense strand to approximately 65 and 42 bp respectively upstream of the transcription startpoint. A mutant tyrT promoter, tyrTp27, is protected more extensively, RNA polymerase interactions extending to at least approximately -130. We propose that these upstream interactions of RNA polymerase perform two functions; activating initiation by polymerase bound at the primary binding site and increasing the concentration of polymerase in the vicinity of the tyrT promoter, thus allowing a high rate of maximal expression and enabling the promoter to be regulated over a wide range of activity.
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PMID:RNA polymerase interactions with the upstream region of the E. coli tyrT promoter. 619

The increase of the contour length of the low molecular linear duplex DNA in the complex with an alkaloid sanguinarine has been evidenced by the viscometric method. The enzymatic hydrolysis of modified DNA by pancreatic deoxyribonuclease I and RNA synthesis of DNA by rat liver nuclear RNA polymerase were studied. Sanguinarine has been shown to inhibit the first stages of DNA hydrolysis. This alkaloid is a weaker inhibitor than ethidium bromide, a more potent inhibitor than actinomycin D and exerts an inhibiting effect similar to that of distamycin A. Sanguinarine also decreases the rate of the labelled precursor incorporation into the acid-insoluble fractions by nuclear RNA polymerase from rat liver. A 50% inhibition by sanguinarine was observed at the same alkaloid concentration as that of ethidium bromide.
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PMID:[Inhibition of the reactions of DNA hydrolysis and RNA synthesis by the alkaloid sanguinarine]. 620 Nov 96

A Saccharomyces cerevisiae protein fraction which binds specifically to the internal promoter regions of genes that are transcribed by RNA polymerase III is shown to function as a transcription factor. We postulate that the stable DNA binding of the factor confers stability on polymerase III transcription complexes. Analysis of the binding by DNase 'foot-printing' distinguishes three segments of the S. cerevisiae tRNALeu3 gene: a region surrounding the so-called A block of the internal promoter, a region surrounding the B block and an intermediate segment. Binding to the A and B block regions is connected, but the B block region exerts a dominant effect.
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PMID:Differential binding of a S. cerevisiae RNA polymerase III transcription factor to two promoter segments of a tRNA gene. 623 42


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