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)

A protein closely related to SV40 T antigen was purified in a biologically active form from cells infected with the defective adenovirus-SV40 hybrid, Ad2+D2. This 107,000 dalton hybrid protein binds and protects a specific portion of SV40 DNA from digestion by pancreatic DNAase I. Hybridization, endonuclease cleavage and pyrimidine tract analysis of the protected fragments reveal that the D2 hybrid protein binds in a sequential manner to tandem recognition sites which lie within a sequence of 120 nucleotides at position 67 near the origin of SV40 replication.
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PMID:The binding site on SV40 DNA for a T antigen-related protein. 20 98

The induction and removal of sites sensitive to T4 endonuclease V from ultraviolet-irradiated Simian Virus 40 (SV40) Form I (supercoiled) DNA during a lytic infection of monkey CV-1 cells was investigated by agarose tube gel electrophoresis. Endonuclease-sensitive sites were induced at a rate of 0.049 sites/SV40 genome per J/m2, or 1.4 sites/1 . 10(8) daltons of DNA per J/m2. This value is similar to the yield of endonuclease-sensitive sites and pyrimidine dimers in uninfected host CV-1 cell DNA. Removal of endonuclease-sensitive sites was dose dependent and non-linear for at least 24 h after irradiation. These results suggest that SV40 DNA is subject to the excision repair mechanisms of the host cell, and that the excision of pyrimidine dimers may be one of the biochemical events underlying host cell reactivation.
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PMID:Removal of T4 endonuclease V-sensitive sites from SV40 DNA after exposure to ultraviolet light. 22 24

The relationship between pyrimidine dimers (measured as endonuclease-sensitive sites) and newly-synthesized DNA has been examined in several different ways, with the following results:- 1. After UV-irradiation of normal human fibroblasts the frequency of pyrimidine dimer sites in sections of DNA which have been synthesized immediately before the UV-irradiation is similar to that in the bulk DNA. 2. The frequency of pyrimidine dimer sites in the parental strands of replicating DNA in UV-irradiated normal human fibroblasts is similar to that in the bulk DNA. 3. In UV-irradiated XP variant cells the size of DNA synthesized in the presence of caffeine immediately after UV irradiation accurately corresponds with the average interdimer distance in the parental DNA. This suggests that in this experimental situation each pyrimidine dimer gives rise to a disocntinuity or a termination site in the daughter strand.
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PMID:The relationship between pyrimidine dimers and replicating DNA in UV-irradiated human fibroblasts. 23 65

An endonuclease acting on DNA exposed to ultraviolet light or gamma-rays has been extensively purified from calf thymus. The enzyme has a pH optimum at pH 7.0-7.5, acts with equal efficiency in the presence of EDTA or divalent cations (Mg-2+ or Ca-2+), is inhibited by NaCl and tRNA and is inactivated by incubation at 50 degrees C. Its molecular weight, determined by Sephadex chromatography or sodium dodecylsulfate gel electrophoresis, is approx. 30 000. The enzyme catalyzes the formation of breaks with 5'-phosphate termini in double-stranded DNA irradiated with ultraviolet or gamma-rays. It does not act on unirradiated DNA or denatured DNA. Since in all these properties the enzymatic activity on ultraviolet- and gamma-irradiated DNA behaved similarly and since the two activities cochromatographed in all systems used during purification, we conclude that they are associated with the same protein. The site of action of the enzyme in ultraviolet-irradiated DNA is a photoproduct other than pyrimidine dimers. Such a photoproduct can also be induced by irradiation of the DNA in vivo, i.e. within the cells.
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PMID:Purification and characterization of an endonuclease from calf thymus acting on irradiated DNA. 23 41

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

Photoalkylation of circular covalently closed DNA from phage PM2 with isopropyl alcohol by using a free radical photoinitiator and UV light of lambda greater than 305 nm led to the specific 8-substitution of purine moieties in the DNA, yielding 8-(2-hydroxy-2-propyl)adenine and 8-(2-hydroxy-2-propyl)guanine as the only detectable damage in the DNA. Using this specifically photoalkylated DNA as a substrate, we discovered in extracts of Micrococcus luteus an endonucleolytic activity that is directed towards 8-(2-hydroxy-2-propyl) purines in DNA. The activity is not a combination of a DNA-glycosylase and an apurinic site endonuclease. It is not inhibited by single-stranded DNA, by UV- or gamma-irradiated single-stranded DNA, or by normal or depurinated double-stranded DNA. however, gamma- or UV-(254 nm) irradiated double-stranded DNAs to inhibit the activity, hinting at the possibility of a common type of lesion in these damaged DNAs. Divalent cations are not required for the incising activity, and it is fully active in 1 mM EDTA, whereas caffeine and ATP cause inhibition. Extracts of mutant M. luteus lacking pyrimidine-dimer-directed endonucleases were found to contain the endonucleolytic activity in levels comparable to those present in the wild type. After the incision, we could demonstrate the specific excision of the 8-alkylated purines from the damaged DNA. The special conformational consequences of the 8-alkylation of purines, at the nucleotide level, namely their nonregular syn conformation, suggest that it is the distortion in the DNA that is recognized by the endonuclease.
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PMID:Endonucleolytic activity directed towards 8-(2-hydroxy-2-propyl) purines in double-stranded DNA. 29 58

Deoxyribonucleic acid (DNA) from bacteriophage T7 has been used to monitor the capacity of gently lysed extracts of Escherichia coli to perform repair resynthesis after ultraviolet (UV) irradiation. Purified DNA damaged by up to 100 J of UV radiation per m2 was treated with an endonuclease from Micrococcus luteus that introduces single-strand breaks in irradiated DNA. This DNA was then used as a substrate to study repair resynthesis by extracts of E. coli. It was found that incubation with the extract and exogenous nucleoside triphosphates under suitable assay conditions resulted in removal of all pyrimidine dimers and restoration of the substrate DNA to its original molecular weight. Repair resynthesis, detected as nonconservative, UV-stimulated DNA synthesis, was directly proportional tothe number of pyrimidine dimers introduced by radiation. The repair mode described here appears to require DNA polymerase I since it does no occur at the restrictive temperature in polA12 mutants, which contain a thermolabile polymerase. The addition of purified DNA polymerase I to extracts made from a polA mutant restores the ability to complete repair at the restrictive temperature.
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PMID:Deoxyribonucleic acid repair in vitro by extracts of Escherichia coli. 32 26

Two rad mutants of yeast, rad10 and rad16, are shown to be defective in the removal of UV-induced pyrimidine dimers since DNAs obtained from irradiated cells following a post-irradiation incubation in the dark still retain UV-endonuclease-sensitive sites. Both rad10 and rad16 mutants are in the same pathway of excision-repair as the rad1, rad2, rad3 and rad4 mutants.
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PMID:Defective thymine dimer excision in radiation-sensitive mutants rad10 and rad16 of Saccharomyces cerevisiae. 32 68

Py pyrimidine dimers Py correndonucleases I and II from Micrococcus luteus act exclusively on thymine-thymine, cytosine-cytosine, and thymine-cytosine cyclobutyl dimers in DNA, catalyzing incision 5' to the damage and generating 3'-hydroxyl and 5'-phosphoryl termini. Both enzymes initiate excision of pyrimidine dimers in vitro by correxonucleases and DNA polymerase I. The respective incised DNAs, however, differ in their ability to act as substrate for phage T4 polynucleotide ligase or bacterial alkaline phosphatase, suggesting that each endonuclease is specific for a conformationally unique site. The possibility that their respective action generates termini which represent different degrees of single strandedness is suggested by the unequal protection by Escherichia coli binding protein from the hydrolytic action of exonuclease VII.
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PMID:Micrococcus luteus correndonucleases. II. Mechanism of action of two endonucleases specific for DNA containing pyrimidine dimers. 33 May 26

When DNA from bacteriophage T7 is irradiated with UV light, the efficiency with which this DNA can be packaged in vitro to form viable phage particles is reduced. A comparison between irradiated DNA packaged in vitro and irradiated intact phage particles shows almost identical survival as a function of UV dose when Escherichia coli wild type or polA or uvrA mutants are used as the host. Although uvrA mutants perform less host cell reactivation, the polA strains are identical with wild type in their ability to support the growth of irradiated T7 phage or irradiated T7 DNA packaged in vitro into complete phage. An examination of in vitro repair performed by extracts of T7-infected E.coli suggests that T7 DNA polymerase may substitute for E. coli DNA polymerase I in the resynthesis step of excision repair. Also tested was the ability of a similar in vitro repair system that used extracts from uninfected cells to restore biological activity of irradiated DNA. When T7 DNA damaged by UV irradiation was treated with an endonuclease from Micrococcus luteus that is specific for pyrimidine dimers and then was incubated with an extract of uninfected E. coli capable of removing pyrimidine dimers and restoring the DNA of its original (whole genome size) molecular weight, this DNA showed a higher packaging efficiency than untreated DNA, thus demonstrating that the in vitro repair system partially restored the biological activity of UV-damaged DNA.
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PMID:In vitro packaging of UV radiation-damaged DNA from bacteriophage T7. 33 Aug 77


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