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)

The ultraviolet-light induction of DNA damage has been measured in the epidermis of hairless mice with the use of damage-specific endonucleases from Micrococcus luteus. The rates of induction of endonuclease-sensitive sites in HRS/J/Anl and Skh:hairless-1 mice were 6.1 +/- 0.5 X 10(-11) and 6.5 +/- 0.8 X 10(-11)/dalton/J/sq m from a FS40 fluorescent sun lamp (280 to 400 nm), respectively. Enzymatic photoreactivation with yeast photoreactivating enzyme showed that approximately 80% of the endonuclease-sensitive sites were cycloburyl pyrimidine dimers. In both strains of mice the pyrimidine dimers remained in high-molecular-weight DNA for 24 hr after irradiation. These data show that mouse epithelial cells in vivo have little or no capacity for the excision repair of pyrimidine dimers.
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PMID:Induction and persistence of pyrimidine dimers in the epidermal DNA of two strains of hairless mice. 88 73

The complex bis(phenanthrenequinone diimine)(bipyridyl)rhodium(III), Rh(phi)2(bpy)3+, cleaves DNA efficiently in a sequence-neutral fashion upon photoactivation so as to provide a novel, high resolution, chemical photofootpring reagent. Photofootprinting of two crystallographically characterized DNA-binding agents, distamycin, a small natural product which binds to DNA in the minor groove, and the endonuclease EcoRI, which binds in the major groove, gave respectively a 5-7 base pair footprint for the drug at its A6 binding site and a 10-12 base pair footprint for the enzyme centered at its recognition site (5'-GAATTC-3'). Both footprints agree closely with the crystallographic results. The photocleavage reaction can be performed using either a high intensity lamp or, conveniently, a simple transilluminator box, and the photoreaction is not inhibited by moderate concentrations of reagents which are sometimes required for examining interactions of molecules with DNA. When compared with other popular footprinting agents, the rhodium complex shows a number of distinct advantages: sequence-neutrality, high resolution, ability to footprint major as well as minor groove-binding ligands, applicability in the presence of additives such as Mg2+ or glycerol, ease of handling, and a sharply footprinted pattern. Light activated footprinting reactions furthermore offer the possibility of examining DNA-binding interactions with time resolution and within the cell.
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PMID:High resolution footprinting of EcoRI and distamycin with Rh(phi)2(bpy)3+, a new photofootprinting reagent. 260 52

Cyclobutyl pyrimidine dimers have been detected in the DNA of human skin following in vivo irradiation with suberythemal doses of ultraviolet (UV) radiation from FS-20 sun lamp fluorescent tubes. Dimers were assayed by treatment of extracted DNA with Micrococcus luteus UV-specific endonuclease, alkaline agarose electrophoresis, and ethidium bromide staining. This technique, in contrast to conventional dimer assays, can be used with nonradioactive DNA and is optimal at low UV light doses. M. luteus endonuclease-sensitive sites were determined after exposure of untanned skin in two volunteers to UV light (0.97, 1.94, or 3.88 X 10(3) J/sq m; lambda, 290 to 360 nm). At 20 min postirradiation (dose, 1.94 X 10(3) J/sq m), fewer M. luteus endonuclease-sensitive sites were found in the DNA than immediately after the irradiation. Even fewer endonuclease-sensitive sites were found at 20 min when the UV-irradiated skin was subsequently irradiated with visible light than when the area was kept in the dark. These data suggest that some dimer disappearance by excision repair occurs within 20 min of UV irradiation and that photoreactivation of dimers can make a contribution to the total repair process.
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PMID:Pyrimidine dimer formation and repair in human skin. 625 56

The induction and loss of pyrimidine dimers in human skin in vivo was determined using UV endonuclease, alkaline sucrose sedimentations, and the fluorescent detection of nonradiolabeled DNA. The number of dimers induced following exposure of the skin to radiation emitted from a Burdick UV-800 sunlamp was quantitated by reacting the extracted DNA with Micrococcus luteus endonuclease specific for pyrimidine dimers. Exposure to 15 and 30 seconds of radiation emitted from this lamp produced the formation of 12.8 and 23.6 dimers per 10(8) daltons DNA, respectively. Approximately 50% of the dimers induced were lost 58 min after irradiation. Only a small percentage (less than 10) remained 24 hr postirradiation. These data partially characterize the process by which pyrimidine dimers are excised from human skin DNA in vivo.
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PMID:Excision repair of UV-induced pyrimidine dimers in human skin in vivo. 626 41

The induction and fate of pyrimidine dimers and unscheduled DNA synthesis were measured in u.v.-irradiated primary, newborn SENCAR mouse epithelial cells. Unscheduled DNA synthesis was induced in a dose responsive manner by two u.v. sources, a germicidal lamp (254 nm) and an FS40 sunlamp (280--400 nm). Using the endonuclease-sensitive site assay to detect pyrimidine dimer production and excision, we examined the response of the newborn mouse cells to both u.v. sources. We were unable to detect the removal of pyrimidine dimers with either of the two sources of u.v. The speculation is made that primary, newborn mouse epidermal cells excise u.v.-induced pyrimidine dimers to an extent below the level of detection of the endonuclease-sensitive site assay but to an extent sufficient to induce unscheduled DNA synthesis.
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PMID:Induction of pyrimidine dimers and unscheduled DNA synthesis in cultured mouse epithelial cells exposed to 254-nm- and u.v.-B radiation. 687 46

The numbers of ultraviolet light (UV)-induced pyrimidine dimers in the DNA of neonatal BALB/c mouse skin were measured by assessing the sensitivity of the DNA to Micrococcus luteus UV endonuclease. Irradiation of neonatal BALB/c mice with FS40 sunlamps caused a dose-dependent induction of endonuclease-sensitive sites (pyrimidine dimers) in DNA extracted from back skin. Exposure of these UV-irradiated neonatal mice to photoreactivating (PR) light ("cool white" fluorescent lamp and incandescent lamp) caused a reduction in the number of pyrimidine dimers in the DNA, as revealed by a shift in low-molecular-weight DNA to high-molecular-weight DNA. In contrast, DNA profiles of the skin of either UV-irradiated mice or UV-irradiated mice kept in the dark for the same duration as those exposed to PR light did not show a loss of UV-induced endonuclease-sensitive sites. Furthermore, reversing the order of treatment, i.e., administering PR light first and then UV, did not produce a reduction in pyrimidine dimers. These results demonstrate that PR or UV-induced pyrimidine dimers occurs in neonatal BALB/c mouse skin. The optimal wavelength range for in vivo PR appears to be in the visible region of the spectrum (greater than 400 nm). Although dimer formation could be detected in both dermis and epidermis, PR occurred only in the dermis. Furthermore, the PR phenomenon could not be detected in the skin of adult mice from the same inbred strain.
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PMID:Photoreactivation of ultraviolet radiation-induced pyrimidine dimers in neonatal BALB/c mouse skin. 721 50

Unstimulated human T lymphocytes are exquisitely sensitive to UVB irradiation. This hypersensitivity appears to relate to low deoxyribonucleotide pool sizes. They have also been reported to be defective in global excision of cyclobutane pyrimidine dimers, but such experiments may have been carried out at supralethal doses, where unrepaired excision breaks persist indefinitely. We use a T4 endonuclease Comet assay to show that removal of cyclobutane pyrimidine dimers is defective in the unstimulated mononuclear cell fraction (mainly T lymphocytes) even at sublethal fluences from an FS20 broad spectrum UVB lamp. Moreover, removal is not enhanced by addition of deoxyribonucleosides to the medium. Cells which are failing to remove cyclobutane pyrimidine dimers readily form fresh incision breaks in response to a second UVB fluence, indicating that they retain repair capacity and suggesting that removal of types of damage other than cyclobutane pyrimidine dimers is effective.
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PMID:Repair of cyclobutane pyrimidine dimers in unstimulated human mononuclear cells is deficient at very low fluences of ultraviolet B and is not enhanced by addition of deoxyribonucleosides. 971 71

Photoreactivation of Escherichia coli after inactivation by a low-pressure (LP) UV lamp (254 nm), by a medium-pressure (MP) UV lamp (220 to 580 nm), or by a filtered medium-pressure (MPF) UV lamp (300 to 580 nm) was investigated. An endonuclease sensitive site (ESS) assay was used to determine the number of UV-induced pyrimidine dimers in the genomic DNA of E. coli, while a conventional cultivation assay was used to investigate the colony-forming ability (CFA) of E. coli. In photoreactivation experiments, more than 80% of the pyrimidine dimers induced by LP or MPF UV irradiation were repaired, while almost no repair of dimers was observed after MP UV exposure. The CFA ratios of E. coli recovered so that they were equivalent to 0.9-, 2.3-, and 1.7-log inactivation after 3-log inactivation by LP, MP, and MPF UV irradiation, respectively. Photorepair treatment of DNA in vitro suggested that among the MP UV emissions, wavelengths of 220 to 300 nm reduced the subsequent photorepair of ESS, possibly by causing a disorder in endogenous photolyase, an enzyme specific for photoreactivation. On the other hand, the MP UV irradiation at wavelengths between 300 and 580 nm was observed to play an important role in reducing the subsequent recovery of CFA by inducing damage other than damage to pyrimidine dimers. Therefore, it was found that inactivating light at a broad range of wavelengths effectively reduced subsequent photoreactivation, which could be an advantage that MP UV irradiation has over conventional LP UV irradiation.
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PMID:Photoreactivation of Escherichia coli after low- or medium-pressure UV disinfection determined by an endonuclease sensitive site assay. 1245 Aug 25

Photoreactivation of Legionella pneumophila after the inactivation by low-pressure (LP) or medium-pressure (MP) UV lamp was investigated in comparison with that of Escherichia coli. An endonuclease sensitive site (ESS) assay was used to determine the number of UV-induced pyrimidine dimers in the genome DNA of L. pneumophila or E. coli, while the survival ratio of each bacterium was also investigated by cultivation methods. L. pneumophila performed photoreactivation with almost complete repair of pyrimidine dimers associated with the quick recovery of survival ratio. A 3 log inactivation of L. pneumophila by LP or MP UV lamp was, respectively, resulted in 0.5 log or 0.4 log inactivation when photoreactivation was completed. Interestingly, L. pneumophila performed equivalent photoreactivation after LP and MP UV lamp exposures while photoreactivation of E. coli was significantly repressed after the inactivation by MP UV lamp. This study indicated that an attention would be required to design and operate a UV disinfection system targeting L. pneumophila. It was further implied that E. coli would not correctly indicate the fate of L. pneumophila in UV disinfection systems when photoreactivation takes place.
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PMID:Photoreactivation of Legionella pneumophila after inactivation by low- or medium-pressure ultraviolet lamp. 1520 6

Photoreactivation of Escherichia coli K12 (IFO 3301), in the presence or absence of yeast extract (YE), was investigated after inactivation by low-pressure UV lamp. An endonuclease sensitive site (ESS) assay was used to determine the UV-induced pyrimidine dimers in the genome of E. coli, while a colony-forming ability (CFA) test was also used to examine the survival ratio of E. coli. The YE solution reduced the CFA recovery at a final concentration of 125 mg/L. A dialysis of the YE solution indicated that the YE fraction (with nominal molecular weight >1,000 and <3,500) was effective at repressing the CFA recovery. Interestingly, the repair of ESS was equivalent regardless of the presence of the YE dialysate, while the CFA recovery was significantly repressed in the presence of YE. It was, therefore, suggested that YE components, probably with molecular weights of 1,000-3,500, were effective at repressing the CFA recovery of E. coli without affecting the ESS repair during photoreactivation.
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PMID:Repressive effects of yeast extract on photoreactivation of Escherichia coli. 1531 83


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