Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have developed an alkaline agarose gel method for quantitating single strand breaks in nanogram quantities of nonradioactive DNA. After electrophoresis together with molecular length standards, the DNA is neutralized, stained with ethidium bromide, photographed, and the density profiles recorded with a computer controlled scanner. The median lengths, number average molecular lengths, and length average molecular lengths of the DNAs can be computed by using the mobilities of the molecular length standards. The frequency of single strand breaks can then be determined by comparison of the corresponding average molecular lengths of DNAs treated and not treated with single strand break-inducing agents (radiation, chemicals, or lesion-specific endonuclease). Single strand break yields (induced at pyrimidine dimer sites in uv-irradiated human fibroblasts DNA by the dimer-specific endonuclease from Micrococcus luteus) from our method agree with values obtained for the same DNAs from alkaline sucrose gradient analysis. The method has been used to determine pyrimidine dimer yields in DNA from biopsies of human skin irradiated in situ. It will be especially useful in determining the frequency of single strand breaks (or lesions convertible to single strand breaks by specific cleaving reagents or enzymes) in small quantities of DNA from cells or tissues not amenable to radioactive labeling.
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PMID:Quantitation of radiation-, chemical-, or enzyme-induced single strand breaks in nonradioactive DNA by alkaline gel electrophoresis: application to pyrimidine dimers. 379 60

The Staphylococcus aureus plasmid pSK1 carries Tn4001, a 4.7-kilobase (kb) transposon which specifies resistance to gentamicin, tobramycin, and kanamycin. In addition, pSK1 mediates resistance to trimethoprim and linked resistance to ethidium bromide (Ebr) and to quaternary ammonium compounds (Qar). Restriction endonuclease analysis of pSK1 and a deleted derivative of pSK1 revealed that the gene(s) responsible for Ebr Qar lies within a 5.2-kb HindIII fragment. This fragment has been cloned into the Escherichia coli plasmid vector pBR322, and transformants of an E. coli K-12 strain exhibited Ebr Qar. Subcloning of the 5.2-kb insert, combined with data from electron microscopic analysis of deleted derivatives of pSK1, located the Ebr Qar determinant(s) on a 2.3-kb segment of pSK1 DNA.
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PMID:Cloning and expression of Staphylococcus aureus plasmid-mediated quaternary ammonium resistance in Escherichia coli. 388 46

We have investigated whether mammalian cells can repair pyrimidine dimers in their mitochondrial DNA which have been induced by ultraviolet light. The assay system is based upon the ability of the phage T4 UV endonuclease to nick covalently closed circular mitochondrial DNA that contain pyrimidine dimers. Our results show that dimers are not removed from the mitochondrial DNA of mouse L cells or human KB and HeLa cells. There is also no evidence for photoreactivation of mitochondrial DNA. Analyses of ethidium bromide-cesium chloride equilibrium density gradients of mitochondrial DNA isotopically labeled before and after exposure to ultraviolet light show that the total amount of DNA replication is depressed after exposure. In addition, an increase in the frequency of molecules banding at a position expected for intermediate replicating forms and open circular daughter molecules suggests that the rate of replication is slower (or arrested) in molecules with pyrimidine dimers. The absence of a significant amount of mixing of label incorporated before and after ultraviolet-irradiation is evidence against the occurrence of a large amount of genetic exchange between mitochondrial DNA molecules under these conditions.
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PMID:The absence of a pyrimidine dimer repair mechanism in mammalian mitochondria. 421 85

Temperate bacteriophages of Bacillus subtilis were characterized according to host range and digestion of the bacteriophage genome by endonuclease EcoRI. The three bacteriophages, phi3T, SPO2, and phi105, were all heteroimmune, and the DNA digests showed dissimilar patterns by agarose-ethidium bromide gel electrophoresis.
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PMID:Characterization of temperate bacteriophages of Bacillus subtilis by the restriction endonuclease EcoRI: evidence for three different temperate bacteriophages. 421 7

JC virus was found to have a buoyant density of 1.20 g/cm(3) in linear sucrose-D(2)O and 1.35 g/cm(3) in cesium chloride isopycnic gradients. DNA extracted either from JC-infected cultures or from gradient-purified virions occupied a dense position relative to linear DNA in cesium chloride/ethidium bromide gradients, and the circular configuration of the extracted DNA was confirmed by electron microscopy, with a measured molecular weight of 2.93 x 10(6). DNA from BK virus was similarly prepared and compared to JC and to an SV40 DNA standard by digestion with restriction endonuclease preparations from Haemophilus influenzae, Haemophilus parainfluenzae, and Escherichia coli. Digests were electrophoretically analyzed on gradient polyacrylamide slab gels or agarose gels, and the three viruses were found to have distinctly different cleavage patterns by this form of analysis: JC and BK viruses were almost entirely different from SV40 and significantly different from each other. Thus, JC and BK human papovaviruses appear to be discrete new members of the papovavirus group, rather than SV40 variants.
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PMID:Comparison of JC and BK human papovaviruses with simian virus 40: restriction endonuclease digestion and gel electrophoresis of resultant fragments. 436 64

RNA covalently linked to double-stranded RNA (dsRNA) is preferentially degraded in extracts of interferon-treated HeLa cells [Nilsen, T. W., & Baglioni, C. (1979) Proc. Natl. Acad. Sci. U.S.A. 76, 2600-2604]. The size of the dsRNA required for this preferential degradation has been determined by annealing poly(I) of known length to the poly(C) tract of encephalomyocarditis virus (EMCV) RNA or by annealing poly(U) to poly(A) of known length of vesicular stomatitis virus mRNA. The dsRNA must be longer than about 60 base pairs to observe the preferential degradation of RNA. Moreover, triple-stranded regions that do not activate synthesis of 2',5'-oligo(A) and ethidium bromide, which intercalates in dsRNA and blocks 2',5'-olido(A) polymerase activation, prevent this degradation. Ethidium also blocks the degradation of the replicative intermediate of EMCV by extracts of interferon-treated cells. These experiments indicate that synthesis of 2',5'-oligo(A) is required for the degradation of RNA linked to dsRNA. The 2',5'-oligo(A)-dependent endonuclease does not cleave single- or double-stranded DNA, nor does it cleave homopolyribonucleotides. The potential role of the 2',5'-oligo(A) polymerase/endonuclease system in the inhibition of viral RNA replication is discussed.
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PMID:Role of 2',5'-oligo(adenylic acid) polymerase in the degradation of ribonucleic acid linked to double-stranded ribonucleic acid by extracts of interferon-treated cells. 616 40

The fragmentation of Hind III- and Pst I-digested PM2 DNA and of Hind III-digested pBR322 DNA by bleomycin A2 and B2 and talisomycins A, B, S2b, and S10b was investigated. As observed by electrophoresis on agarose gels, the ethidium bromide staining band patterns produced following incubation of the various restriction endonuclease-digested DNAs with the compounds were different for the bleomycin analogs and for the talisomycin analogs. Quantitation of the degree of fragmentation of various segments of linear PM2 DNA by either bleomycin A2 or talisomycin A indicated that certain segments of the PM2 genome serve as better substrates than other segments for double-strand fragmentation by either of the two antitumor antibiotics. These results show that in this system bleomycin and talisomycin analog treatment of linear PM2 or pBR322 DNA resulted in breakage of DNA, producing different-length DNA fragments, and demonstrate the importance of the two amino acids and the 4-amino-4,6-dideoxy-L-talose sugar, which are located near the bithiazole in talisomycin but absent in the bleomycin structure in conferring a different site-specificity for DNA fragmentation to talisomycin than to bleomycin.
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PMID:Structure-activity relationships involved in the site-specific fragmentation of linear duplex DNAs by talisomycin and bleomycin analogs. 617 26

Heterogeneous nuclear RNA contains double-stranded regions that are not found in mRNA and that may serve as recognition elements for processing enzymes. The double-stranded regions of heterogeneous nuclear RNA prepared from HeLa cells promoted the synthesis of (2',5')oligoadenylate [(2',5')oligo(A) or (2'5')An] when incubated with (2',5')An polymerase. This enzyme is present in elevated levels in interferon-treated cells, and labeled heterogeneous nuclear RNA incubated with extracts of these cells is preferentially cleaved, since mRNA included in the same incubations is not appreciably degraded. The cleavage of heterogenous nuclear RNA is caused by the synthesis of (2'5')An and by a "localized" activation of the (2',5')An-dependent endonuclease, since it was enhanced by ATP, the substrate of the (2',5')An polymerase, and inhibited by 2'-dATP and ethidium bromide. Both of these compounds suppress the synthesis of (2',5')An, the first by competitive inhibition and the latter by intercalating into double-stranded RNA. The possible role of double-stranded regions and of the (2',5')An polymerase-endonuclease system in the processing of heterogeneous nuclear RNA is discussed.
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PMID:Heterogeneous nuclear RNA promotes synthesis of (2',5')oligoadenylate and is cleaved by the (2',5')oligoadenylate-activated endoribonuclease. 618 Mar

A procedure for rapid, preparative purification of plasmid DNA is described and compared with a conventional equilibrium centrifugation method. A discontinuous, two-step CsCl-ethidium bromide gradient is used, with the starting position of the plasmid-containing extract being at the bottom of the tube. During centrifugation in a fixed angle rotor, covalently closed circular plasmid DNA is separated from contaminating protein, RNA, and chromosomal DNA in 5 hr. Plasmids purified by this method are considerably less contaminated with RNA than when purified by a 48-hr equilibrium run in a homogeneous gradient, as determined by agarose gel electrophoresis and 5'-end-labeling studies. Plasmid DNA purified in two-step gradients can be used directly for restriction endonuclease analysis and DNA sequencing.
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PMID:Rapid purification of plasmid DNA by a single centrifugation in a two-step cesium chloride-ethidium bromide gradient. 619 24

By centrifuging total cellular DNA derived from human genital warts (condylomata acuminata) in CsCl-ethidium bromide gradients, supercoiled DNA was isolated. The molecular weight of this DNA was determined by agarose gel electrophoresis and amounted to 5.1 X 10(4). This DNA isolated from an individual genital wart was annealed to fractions of aqueous supernatants of the same wart after prior centrifugation of this material in CsCl density gradients. Annealing was observed at a density of approximately 1.32 g/ml corresponding to the expected density of papilloma virus particles. Since such particles were also observed in the same preparation by electron microscopy, it was concluded that the supercoiled DNA molecules were derived from papilloma virus nucleocapsids. Positive hybridization was found with six additional preparations from individual genital warts. Therefore, it seems that the isolated DNA prevails in condylomata acuminata. The DNA is different from the other five types of human papilloma viruses described thus far in regard to its restriction endonuclease cleavage patterns. The virus analyzed is tentatively designated as human papilloma virus type 6 (HPV 6).
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PMID:Partial characterization of viral DNA from human genital warts (Condylomata acuminata). 624 10


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