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:3.1.21.1 (DNase)
7,655 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A new DNA endonuclease has been purified 3000-fold from Escherichia coli. The enzyme specifically catalyzes the formation of single strand breaks at apurinic and apyrimidinic sites in DNA, but has no activity on intact or single-stranded DNA. Further, the enzyme shows little or no activity on heavily ultraviolet-irradiated DNA, but cleaves x-irradiated DNA, presumably at apurinic and apyrimidinic sites introduced by the radiation treatment. The enzyme, which is tentatively named endonuclease IV, has no detectable associated exonuclease or DNA N-glycosidase activity and does not seem to be identical with any previously known E. coli endonuclease. Endonuclease IV has no Mg2+ requirement, and is fully active in the presence of EDTA. Enzyme activity is stimulated by 0.2 to 0.3 M NaCl and is unusually salt-resistant. Further, the enzyme is fairly heat-stable, and is not inhibited by tRNA. The sidimentation coefficient, S(o)20,w, is 3.4 S. It seems that endonuclease IV is active in DNA repair.
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PMID:A new endonuclease from Escherichia coli acting at apurinic sites in DNA. 1 2

An acid ribonuclease has been purified from HeLa cell lysosomes. The specific activity of the RNase in lysosomes is 8-fold higher than that in nuclei and 15-fold higher than that in the postlysosomal fraction. The purified enzyme showed no detectable DNase, phosphodiesterase, phosphatase, or alkaline RNase activity. The acid RNase binds to Con A-agarose and is inferred to be a glycoprotein. It has a low isoelectric point at pH 3.0 to 3.5, and the optimal pH for activity is between 5.0 and 5.5. The enzyme requires no divalent cation for optimal activity and is totally inhibited by 1 mM Cu2+ or Hg2+. Monovalent cations including Na+, K+, and NH4+ stimulate the activity in low ionic strength buffer. The enzyme degrades rRNA faster than tRNA, and tRNA faster than poly(U); poly(A) and poly(C) are highly resistant. The products from rRNA are mostly oligonucleotides with 3'-phosphate ends. An acid RNase is also present in the lysosomes of L-cells grown in a medium free of serum; it is probably identical to the one described here.
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PMID:Acid ribonuclease from HeLa cell lysosomes. 3 88

A ribonuclease (ribonucleate 3-pyrimidine-oligonucleotidohydrolase, EC 3.1.4.22) was purified 8300-fold from soluble fraction of beef brain and its properties were investigated. The enzyme is an endonuclease capable of hydrolyzing tRNA, rRNA, poly(C), but shows no activity towards poly(U), poly(A), and poly(G). The preparation is free of deoxyribonuclease, non-specific phosphodiesterase and phosphomonoesterase activity. The enzyme has a pH optimum of 7.6, is not heat stable, has a molecular weight of 25 000, and has a K-m of 134 mu rRNA and K-m of 1600 mug poly(C) per ml.
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PMID:Purification of an alkaline ribonuclease from soluble fraction of beef brain. 23 61

By gel filtration on Sephadex G-100, the formation of the complex of chromatin DNase-tRNA has been detected. The complex is reactivated after RNase treatment. The molecular weight of the enzyme-inhibitory complex is estimated to be 85,000.
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PMID:[Detection of the complex of chromatin DNase-tRNA by gel filtration]. 53 14

A substance inhibitory to protein synthesis was purified from mouse skeletal muscle by gel filtration and ion-exchange chromatography, as well as by centrifugation on sucrose gradients. The molecular weight of the inhibitor, determined by sodium dodecyl sulphate/polyacrylamide-gel electrophoresis, was 71000. The inhibitory activity was insensitive to ribonuclease A, deoxyribonuclease I and phospholipase C. It was sensitive to Pronase treatment but insensitive to heat-treatment and trypsin degradation. The present results, taken together with previous studies, indicate that the site of action of the inhibitor is not on the initiation phase of protein synthesis but rather at a step after the binding of aminoacyl-tRNA to ribosomes. The increased inhibitor activity found in dystrophic muscle is discussed.
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PMID:Studies of a factor from dystrophic mouse muscle inhibitory towards protein synthesis. 74 60

Arginine was transferred from arginyl-tRNA to the amino-terminal end of chromatin proteins by L-arginyl-transferase. The reaction was dependent on the presence of potassium ion and beta-mercaptoethanol and was sensitive to RNase and trypsin. Treatment with DNase partially inhibited the transfer of arginine from arginyl-tRNA suggesting that intact chromatin structure is necessary for modification of chromatin. The radioactivity incorporated into chromatin was sensitive to trypsin but not to DNase or RNase. Most of the incorporated radioactivity was recovered in the phenol fraction, supporting the notion that modification of chromatin takes place in proteins but not in nucleic acids of chromatin. Modification of the proteins by transfer of arginine from arginyl-tRNA takes place mainly in the nonhistone fraction of chromatin. Major portions of chromosomal proteins modified in this manner appear to be released from chromatin. Incubation of incorporated radioactive product with [12C]arginyl-tRNA did not alter the product, showing that incorporated arginine is stable and does not exchange with added arginine or arginyl-tRNA. These observations suggest that aminoacyl-transferase may function in the modification of chromosomal proteins and that modification of chromatin may alter the regulatory mechanisms of cellular functions.
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PMID:Amino-terminal arginylation of chromosomal proteins by arginyl-tRNA. 99 Feb 69

Autoantibody reactive with tRNA was identified by immunoprecipitation of Hela cell extract. Four out of 56 sera from patients with autoimmune chronic active hepatitis (CAH), and four out of 35 sera from patients with primary biliary cirrhosis (PBC) contained antibody directed against gel-purified tRNA in Hela cell extract, but no sera obtained from CAH type B, CAH non-A, non-B, or healthy volunteers did. Further studies on these eight anti-tRNA sera disclosed that 6 of the 8 sera that immunoprecipitated tRNA from Hela cell extract, reacted with purified tRNA, but reacted with neither 5sRNA nor ribosomal RNA species. After proteinase and deoxyribonuclease digestion of Hela cell extract, the epitope for these 6 sera was conserved, and the antigen was sensitive to ribonuclease (anti-tRNA serum). Purified Hela cell DNA digested with Eco RI or Hind III (denatured or non-denatured) could not be immunoprecipitated by these sera. In a patient with autoimmune CAH, the anti-tRNA antibody was weakly positive at week 2 and disappeared 2 months after steroid therapy started, "in parallel" with disappearance of anti-nuclear antibody. In the other 2 sera, the antigen was sensitive to proteinase.
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PMID:Autoantibody specific for transfer ribonucleic acid (tRNA) in patients with autoimmune chronic active hepatitis and primary biliary cirrhosis. 177 87

Transcription factor IIIC (TFIIIC) from Xenopus has been partially purified and characterized. Footprinting analyses indicate that a partially purified TFIIIC fraction contains an activity which specifically recognizes the "B" block element of tRNA gene. In addition, two other regions located downstream from the "B" block sequence are also protected. Protection experiments on 5S genes by DNAase I with either TFIIIC alone or TFIIIA and TFIIIC produced a minimal change in the cleavage pattern implying that TFIIIC does not intimately associate with DNA. The implications of these findings in relation to the class III gene transcription are discussed.
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PMID:Specific interaction of a partially purified Xenopus transcription factor IIIC (TFIIIC) with frog tRNA gene. 224 62

Yeast transcription factor tau interacts with the A and B blocks of the intragenic promoter of tRNA genes. The structure of tau was investigated by identifying the polypeptide chains specifically complexed to the tRNA3Glu gene. Highly purified factor, obtained by an improved purification procedure, contained several polypeptide chains, four of which (Mr = 145,000, 135,000, 100,000 and 65,000) comigrated with tau-DNA complex by polyacrylamide gel electrophoresis. Antibodies raised against the 145- and 100-kDa components altered the migration of tau-DNA complexes in band shift assays and inhibited tRNA synthesis in a reconstituted transcription system. These components are immunologically unrelated proteins. By UV cross-linking to 32P-body-labeled tDNA followed by extensive DNase treatment, two polypeptides of the same size (145 and 100 kDa) were found to be radioactively labeled. Factor tau, therefore, appears to be a multisubunit DNA-binding protein with two distinct polypeptides contributing to DNA recognition. Limited proteolysis of tau generated a protease-resistant tau B (tau B) domain that binds solely to the B block. tau B-tDNA complexes were recognized by anti-145 IgG and contained a 120-kDa polypeptide that could originate from the 145-kDa component by proteolysis. These results strongly suggest that the 145-kDa polypeptide belongs to tau B and is responsible for B block binding.
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PMID:Two polypeptide chains in yeast transcription factor tau interact with DNA. 265 41

Total RNA from Ehrlich ascites mitochondria pretreated with RNase-free DNase was capped in vitro with [alpha-32P]GTP and guanylyl transferase. The cappable RNAs representing the primary transcripts show a heterogeneous size distribution with four major species of 46, 63, 94, and 152 nucleotides and four minor species of 19, 24, 104, and 790 nucleotides in size. Hybridization with the D-loop DNA probes shows that the 19-nucleotide-long capped RNA is coded by the H-strand of mitochondrial DNA while the rest are coded by the L-strand. S1 nuclease mapping and primer extension analyses suggest the occurrence of a transcription initiation of H-strand at about 19 nucleotides upstream from the start of the tRNA(Phe) gene. All of the L-strand cappable RNAs have a common 5' end mapping to nucleotide 16,183 +/- 5 of the genome. The 3' ends of four major cappable RNA species line up to the conserved sequence boxes, putative start sites of DH-DNA; and in fact about 2% of these cappable species are found to exist as DNA-linked RNA under steady-state conditions. The 3' end of the 790-nucleotide cappable RNA lies close to the start of the tRNA(Pro) gene, suggesting that it may be the true precursor of L-strand transcript endonucleolytically processed at the 3' end. The level of L-strand-coded cappable RNAs varies markedly under different growth conditions. Treatment with cycloheximide results in a reduction while chloramphenicol caused over 3-fold induction, suggesting that these "primer" RNAs may have an additional regulatory function.
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PMID:Characterization of primary transcripts and identification of transcription initiation sites on the heavy and light strands of mouse mitochondrial DNA. 271 42


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