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)

The ability to remove ultraviolet (UV)-induced pyrimidine dimers was examined in four radiation-sensitive mutants of Saccharomyces cerevisiae. The susceptibility of DNA from irradiated cells to nicking by either the T4 UV-endonuclease or an endonuclease activity found in crude extracts of Micrococcus luteus was used to measure the presence of dimers in DNA. The rad3 and rad4 mutants are shown to be defective in dimer excision whereas the rad6 and rad9 mutants are proficient in dimer excision.
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PMID:Repair of pyrimidine dimers in radiation-sensitive mutants rad3, rad4, rad6 and rad9 of Saccharomyces cerevisiae. 33 35

A sensitive and quantitative procedure for the detection of pyrimidine dimers in yesast nuclear DNA is described. The assay employs dimer-specific, endonuclease activities from Micrococcus luteus together with DNA sedimentation through calibrated, alkaline sucrose gradients to detect endonuclease-induced, single-strand breaks. Breaks were induced in a dose-dependent manner from 0 to 80 J m-2 at 254 nm and in numbers equivalent to the numbers of dimers induced by similar doses (Unrau et al., Biochim. Biophys. Acta, 312 (1973) 626--632). This procedure also allows the use of [6-3H] uridine to label cellular nucleic acids, but dose not require extensive DNA purification to eliminate concomitantly labeled RNA. Endonuclease-sensitive sites in the wild-type, haploid strain S288C, after irradiation with 5 J m-2 (254 nm), were removed in less than 5 min when cells were incubated in buffer (pH 7.0) at 28 degrees C. After irradiation with doses from 30 to 100 Jm-2 site removal in S288C required longer postirradiation incubations and was about 90% complete. In a radiation-sensitive strain carrying the mutant allele rad4-3 the number of endonuclease-sensitive sites remained constant for 6 h after irradiation with 5 Jm-2. The retention of sites in this strain indicates that it is defective in the excision of pyrimidine dimers.
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PMID:Removal of pyrimidine dimers from Saccharomyces cerevisiae nuclear DNA under nongrowth conditions as detected by a sensitive, enzymatic assay. 34 80

Endonuclease alpha isolated from the nucleus of the yeast Saccharomyces cerevisiae is a DNA endonuclease which has been shown to act preferentially on denatured T7 DNA. The purified enzyme is more active with UV-irradiated native T7 DNA than with unirradiated substrate. The relation between damage, measured by pyrimidine dimer concentration, and excess endonuclease activity is most readily explained by local denaturation caused by presence of pyrimidine dimers. When three radiation sensitive mutants of yeast were tested for the level of endonuclease alpha present, none were found lacking the enzyme. However, nuclei of strain rad 1-1, a mutant that may be defective in heteroduplex repair as well as excision repair, were found to contain reduced levels of the endonuclease. The enzyme isolated from this strain had less than one half the specific activity of similar preparations from wild type yeast.
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PMID:Endonuclease alpha from Saccharomyces cerevisiae shows increased activity on ultraviolet irradiated native DNA. 36 83

The method of isolation and partial purification of DNA-cytosine-methyltransferase (DC-methylase) from E. coli C is described. The enzyme underwent approximately 100-fold purification. The obtained preparation of DC-methylase can be additionally considerably purified by sedimentation in sucrose gradient. Native molecular weight of DC-methylase from E. coli C. is 70,000. The activity of enzyme does not depend on the Mg2+ ions. DC-methylase E. coli C provides DNA of lambda phage in vitro with full resistance against restriction endonuclease EcoRII. In DNA methylated by DC-methylase the modified cytosine, mainly in C-MC and C-MC-T sequences, corresponds to the pyrimidine sequences of specific site EcoRII. DNA of lambda.B phage contains approximately 80 sites for modification by DC-methylase E. coli C. The results obtained point to the same specificity in vitro of DNA-cytosine-methylase E. coli C and DNA-methylase EcoRII.
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PMID:[Isolation and properties of DNA-cytosine methyltransferase from Escherichia coli C]. 37 62

The number of pyrimidine dimers (sites sensitive to UV-endonuclease from M. luteus) transferred at 43 degrees to daughter DNA strands during postreplication repair in UV-irradiated E. coli uvr A polCts was found to be decreased as compared to that after repair at 32 degrees. This indicates the involvement of DNA polymerase III in the sister DNA recombination in UV-irradiated E. coli.
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PMID:Decreased transfer of pyrimidine dimers from parental to daughter DNA strands in UV-irradiated Escherichia coli deficient in DNA polymerase III. 38 55

The ability to remove ultraviolet (UV)-induced pyrimidine dimers from the nuclear DNA of yeast was examined in two radiation-sensitive (rad) mutants and one methyl methanesulfonate-sensitive (mms) mutant of the yeast Saccharomyces cerevisiae. The susceptibility of DNA from irradiated cells to nicking by an endonuclease activity prepared from crude extracts of Micrococcus luteus was used to measure the presence of dimers in DNA. The rad7, rad14 and mms19 mutants were found to be defective in their ability to remove UV-induced dimers from nuclear DNA. All three mutants belong to the same epistatic group as the other mutants involved in excision-repair. All three mutants show enhanced UV-induced mutations. The rad14 mutant also shows epistatic interactions with genes in the other two UV repair pathways.
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PMID:Three additional genes involved in pyrimidine dimer removal in Saccharomyces cerevisiae: RAD7, RAD14 and MMS19. 39 38

Pure cultures of dermal fibroblasts and epidermal keratinocytes have been obtained from a single biopsy of newborn foreskin. The cells were labeled, exposed to several doses of UV light, and allowed to repair in the dark for 16 hr. The number of pyrimidine dimers before and after repair was assessed by measuring the numbers of sites in the DNA sensitive to a specific UV endonuclease. At all doses used, the extent of repair was similar in the cultured keratinocytes and cultured fibroblasts.
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PMID:Repair of ultraviolet light damage to the DNA of cultured human epidermal keratinocytes and fibroblasts. 46 74

Earlier experiments on human cells showed that N-acetoxy-2-acetylaminofluorene mimics ultraviolet radiation in biological and repair characteristics and that the amount of repair from a combined treatment was additive. Chinese hamster V-79 cells are less proficient than human cells in excision repair of pyrimidine dimers resulting from irradiation. We therefore investigated the combined effects of both agents on repair in V-79 cells to see whether they follow the same pattern as in human cells. They did not. Measurements of unscheduled DNA synthesis and the photolysis of DNA repaired in the presence of bromodeoxyuridine gave information about repair due to both agents, and the use of an endonuclease in an extract of Micrococcus luteus allowed us to measure repair of only ultraviolet damage in the presence of N-acetoxy-2-acetylaminofluorene damage. Each technique indicated that the amount of repair from a combined treatment was less than additive and in some cases less than that due to either agent. We conclude that V-79 cells are different from human fibroblasts in the excision repair of both ultraviolet and N-acetoxy-2-acetylaminofluorene damage and suggest that both kinds of damages inhibit repair of damage due to the other agent.
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PMID:DNA repair in V-79 cells treated with combinations of ultraviolet radiation and N-acetoxy-2-acetylaminofluorene. 56 Feb 53

An endonuclease activity isolated from normal, Xeroderma Pigmentosum and De Sanctis-Cacchione fibroblasts by DNA-cellulose chromatography has been evaluated by means of sedimentation analysis both in alkaline and neutral sucrose gradients. The partially purified enzyme is active at pH 7.5 in presence of Mg++ and cleaves UV-irradiated and alkylated DNA. Under identical experimental conditions, the enzyme is not active on untreated, depurinated and heat-denaturated DNA. The specificity on pyrimidine dimers has been further investigated to understand the mechanism of action of the enzyme.
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PMID:Cleavage of damaged DNA by an enzymatic activity from human fibroblasts. 61 1

The incidence of pyrimidine dimer formation and the kinetics of DNA repair in African green monkey kidney CV-1 cells after ultraviolet (UV) irradiation were studied by measuring survival, T4 endonuclease V-sensitive sites, the fraction of pyrimidine dimers in acid-insoluble DNA as determined by thin layer chromatography (TLC), and repair replication. CV-1 cells exhibit a survival curve with extrapolation number n = 7.8 and Do = 2.5 J/m2. Pyrimidine dimers were lost from acid-insoluble DNA more slowly than endonuclease-sensitive sites were lost from or new bases were incorporated into high molecular weight DNA during the course of repair. Growth of CV-1 cultures in [3H]thymidine or X-irradiation (2 or 10 krads) 24 h before UV irradiation had no effect on repair replication induced by 25 J/m2 of UV. These results suggest that pyrimidine dimer excision measurements by TLC are probably unaffected by radiation from high levels of incorporated radionuclides. The endonuclease-sensitive site and TLC measurements can be reconciled by the assumption that pyrimidine dimers are excised from high molecular weight DNA in acid-insoluble oligonucleotides that are slowly degraded to acid-soluble fragments.
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PMID:Excision repair of ultraviolet damage in mammalian cells. Evidence for two steps in the excision of pyrimidine dimers. 65 44


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