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:3.1.30.2 (endonuclease)
18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Site-specific genetic recombinations promoted in vivo by the EcoRI endonuclease has been demonstrated by using constructed hybrid plasmids in which the chloramphenicol resistance gene was inactivated by insertion of DNA fragments at an EcoRI site within the gene. Such recombination can involve either the joining of intracellularly generated cohesive termini of the same DNA fragment or intermolecular ligation of different DNA fragments. DNA cleavage and ligation in vivo are precise: recombinant DNA molecules show functional continuity of the gene sequence cleaved by the enzyme and regeneration of nucleotide recognition sites for both the EcoRI endonuclease and the EcoRI DNA methylase. In other experiments, EcoRI-generated fragments of eukaryotic DNA that had not been modified by the Escherichia coli K methylase were shown to be taken up by bacterial cells and to undergo intracellular ligation to segments of bacterial plasmid DNA.
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PMID:In vivo site-specific genetic recombination promoted by the EcoRI restriction endonuclease. 33 2

An endonuclease having EcoRI specificity is produced by bacteria containing the ColE1 plasmid. Such bacterial cells fail to express restriction or modification functions in vivo, and phage or plasmid DNA obtained from ColE1-containing cells has unmodified EcoRI sites that are cleaved in vitro by purified EcoRI endonuclease or by enzyme extracted from bacteria that carry ColE1. No EcoRI DNA methylase activity associated with ColE1 has been detected. The finding of phenotypically cryptic ColE1-dependent EcoRI endonuclease activity and the absence of any detectable EcoRI modification system in ColE1-containing cells suggest a control mechanism that appears to prevent functional expression of the ColE1-determined enzyme in vivo.
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PMID:Phenotypically cryptic EcoRI endonuclease activity specified by the ColE1 plasmid. 34 63

It was shown that E. coli C, E. coli MRE 600 DNA, and also plasmid DNA of Col E1, RSF 2124 from E. coli K-12, and plasmid DNA from E. coli MRE 600 were completely resistant against restriction endonuclease R. Eco RII. Plasmid DNAs of Col E1, RSF 2124 amplificated for 4 hours in the presence of chloramphenicol are sensitive to R. Eco RII but after 16-hour amplification in the presence of chloramphenicol these DNAs acquire complete resistance against R. Eco RII. These data point to the slower rate of modification of DNA in vivo by DC-methylases of Eco RII type in comparison with DNA methylase Eco RII.
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PMID:[Sensitivity of chromosomal and plasmid E. coli DNA to restriction endonuclease Eco RII]. 36 77

The DNA methylase M.Xbal was isolated from an E. coli recombinant clone. We deduce that the enzyme methylates at the sequence 5'-TCTAGm6A-3'. In combination with the methylation-dependent restriction endonuclease, DpnI (5'-Gm6A/TC-3'), DNA cleavage occurs at the sequence 5'-TCTAGA/TCTAGA-3'. This twelve-base-pair site should occur once every 16,000,000 base pairs in a random sequence of DNA. The exceptional rarity of the M.XbaI/DpnI sequence makes it an ideal candidate for transpositional integration of a unique cleavage site into bacterial genomes. Retrotransposition into mammalian genomes is also an attractive possibility.
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PMID:Cleavage at the twelve-base-pair sequence 5'-TCTAGATCTAGA-3' using M.Xbal (TCTAGm6A) methylation and DpnI (Gm6A/TC) cleavage. 215 82

The gene coding for a CGCG specific DNA methylase has been cloned in E. coli from Brevibacterium epidermidis. The enzyme, named BepI methylase, is probably the cognate methylase of the FnuDII isoschizomer BepI endonuclease isolated from this strain. The expression of BepI methylase in E. coli is dependent on the orientation of the cloned fragment suggesting that the gene is transcribed from a promoter on the plasmid vector. No BepI endonuclease could be detected in the clones producing BepI methylase. The nucleotide sequence of the BepI methylase gene has been determined, it predicts a protein of 403 amino acids (MR: 45,447). Analysis of the amino acid sequence deduced from the nucleotide sequence revealed similarities between the BepI methylase and other cytosine methylases. M. BepI methylates the external cytosine in its recognition sequence.
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PMID:Cloning and structure of the BepI modification methylase. 278 4

Proteins encoded by three genes in the DpnII restriction enzyme cassette of Streptococcus pneumoniae were purified and characterized. Large amounts of the proteins were produced by subcloning the cassette in an Escherichia coli expression system. All three proteins appear to be dimers composed of identical polypeptide subunits. One is the DpnII endonuclease, and the other two are DNA adenine methylase active at 5' GATC 3' sites. Inactivation of enzyme activity by insertions into the genes and comparison of the DNA sequence with the amino-terminal sequence of amino acid residues in the proteins demonstrated the following correspondence between genes and enzymes. The promoter-proximal gene in the operon, dpnM, encodes a 33 X 10(3) Mr polypeptide that gives rise to a potent DNA methylase. The next gene, dpnA, encodes the 31 x 10(3) Mr polypeptide of a weaker and less-specific methylase. The third gene, dpnB, encodes the 34 x 10(3) Mr polypeptide of the endonuclease. Although the endonuclease polypeptide is initiated from an ordinary ribosome-binding site, each of the methylase polypeptide begins at an atypical site with a consensus sequence entirely different from that of Shine & Dalgarno. This presumptive novel ribosome-binding site is well recognized in both S. pneumoniae and E. coli.
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PMID:Proteins encoded by the DpnII restriction gene cassette. Two methylases and an endonuclease. 282 82

Oligodeoxyribonucleotides which form a number of duplexes, containing the recognition sequences for endonuclease BamHI and DNA methylase Eco dam, were synthesised by the phosphotriester approach. Furthermore, synthesis of 3'-phosphorylated oligodeoxyribonucleotides from corresponding S-methyl phosphorothioate triester oligomers is described. The synthetic duplexes are characterized by some defects in the recognition sequences for endonuclease BamHI and methylase Eco dam, viz. nick, absence of an internucleotide phosphate, modifications (including partial single-strandedness) of the recognition site. Interaction of the enzymes with these synthetic substrates was investigated.
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PMID:[Chemical synthesis and properties of oligonucleotide substrates for restriction endonuclease BamHI and methyltransferase Eco dam]. 283 58

Human SY5Y neuroblastoma cells which were differentiated in culture by treatment with 7S murine nerve growth factor for 5 weeks and selection with aphidicolin (L. Jensen, Dev. Biol. 120:56-64, 1987) demonstrated a considerably slower rate of removal of DNA adducts of benzo[a]pyrene, benzo[a]pyrenediolepoxide, and N7-methylguanine than did undifferentiated mitotic cells. A dramatic decline in unscheduled DNA synthesis induced by UV radiation was similarly observed. DNA polymerase beta and uracil DNA glycosylase were unchanged after differentiation, DNA polymerase alpha and DNA methylase decreased roughly threefold, and total apurinic-apyrimidinic endonuclease activity increased roughly threefold after treatment.
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PMID:A reduced rate of bulky DNA adduct removal is coincident with differentiation of human neuroblastoma cells induced by nerve growth factor. 314 94

In order to detect possible m5C photoproducts, highly purified rat liver DNA-cytosine methyltransferase was used to specifically generate m5C with a radioactive methyl group. When these DNAs were subjected to a large dose (10 kJ/m2) of 254 nm or 302 nm ultraviolet light (UVB) to enhance the yield, two labeled photoproducts were detected and isolated by reverse phase HPLC after formic acid hydrolysis. Further studies using acetone as a triplet state sensitizer and UVB irradiation suggested that photoproduct II was activated via a triplet state while the more polar photoproduct I was not. Photoreversion of the purified photoproducts with 10 kJ/m2 254 nm light demonstrated the following reactions: Photoproduct I regenerated m5C, while photoproduct II is split and regenerated m5C and photoproduct I. These results suggest that photoproduct I is monomeric while photoproduct II dimeric, and from the latter's elution position possibly a cyclobutyl type dimer arising from a reaction with an adjacent cytosine. Using d[TTG] and d[Cm5CG] as models of typical sequences, irradiation with 10 kJ/m2 254 nm or 302 nm, respectively, gave rise to a small component having altered mobility in sequencing gels. The altered mobility trinucleotides were resistant to degradation by PI and micrococcal nucleases as expected from photodimerization of the pyrimidine bases. Furthermore, oligonucleotide substrates containing m5C were synthesized and shown to be susceptible to T4 endonuclease v action at locations consistent with d[Cm5C] photodimer formation when irradiated in the UVB range.
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PMID:UV-induced photoproducts of 5-methylcytosine in a DNA sequence context. 337 57

In vivo and in vitro evidence is presented implicating a function of GATC methylation in the Escherichia coli replication origin, oriC, during initiation of DNA synthesis. Transformation frequencies of oriC plasmids into E. coli dam mutants, deficient in the GATC-specific DNA methylase, are greatly reduced compared with parental dam+ cells, particularly for plasmids that must use oriC for initiation. Mutations that suppress the mismatch repair deficiency of dam mutants do not increase these low transformation frequencies, implicating a new function for the Dam methylase. oriC DNA isolated from dam- cells functions 2- to 4-fold less well in the oriC-specific in vitro initiation system when compared with oriC DNA from dam+ cells. This decreased template activity is restored 2- to 3-fold if the DNA from dam- cells is first methylated with purified Dam methylase. Bacterial origin plasmids or M13-oriC chimeric phage DNA, isolated from either base substitution or insertion dam mutants of E. coli, exhibit some sensitivity to digestion by DpnI, a restriction endonuclease specific for methylated GATC sites, showing that these dam mutants retain some Dam methylation activity. Sites of preferred cleavage are found within the oriC region, as well as in the ColE1-type origin.
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PMID:Importance of state of methylation of oriC GATC sites in initiation of DNA replication in Escherichia coli. 389 29


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