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Human repair endonuclease incises DNA at cytosine photoproducts

Conference · · Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States)
OSTI ID:6019840
; ; ;

The nature of DNA damage by uvB and uvC irradiation was investigated using a defined sequence of human DNA. A UV-irradiated, 3'-end-labeled, 92 base pair sequence from the human alphoid segment was incubated with a purified human lymphoblast endonuclease that incises DNA at non-dimer photoproducts. Analysis by polyacrylamide gel electrophoresis identified all sites of endonucleolytic incision as cytosines. These were found in regions of the DNA sequence lacking adjacent pyrimidines and therefore are neither cyclobutane pyrimidine dimers nor 6-4'-pyrimidines. Incision at cytosine photoproducts was not detected at loci corresponding to alkali-labile sites in either control or irradiated substrates. This demonstrates that the bands detected after the enzymic reactions were not the result of DNA strand breaks, base loss sites or ring-opened cytosines. The optimal wavelengths for formation of cytosine photoproducts are 270-295 nm, similar to those associated with maximal tumor yields in animal ultraviolet carcinogenesis studies. Irradiation by monochromatic 254 nm light resulted in reduced cytosine photoproduct formation. This human UV endonuclease has an apparently identical substrate specificity to E. coli endonuclease III. Both the human and bacterial enzymes incise cytosine moieties in UV irradiated DNA and modified thymines in oxidized DNA.

Research Organization:
Temple Univ. School of Medicine, Philadelphia, PA
OSTI ID:
6019840
Report Number(s):
CONF-870644-
Journal Information:
Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Vol. 46:6; ISSN FEPRA
Country of Publication:
United States
Language:
English

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Related Subjects

560120* -- Radiation Effects on Biochemicals
Cells
& Tissue Culture
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AMINES
ANIMALS
AZINES
BIOCHEMICAL REACTION KINETICS
BIOCHEMISTRY
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
CHEMISTRY
CYTOSINE
DNA
DNA REPAIR
DNA SEQUENCING
DNA-ASE
ELECTROMAGNETIC RADIATION
ELECTROPHORESIS
ENDONUCLEASES
ENZYMES
ESTERASES
GENETIC EFFECTS
GENETIC RADIATION EFFECTS
HETEROCYCLIC COMPOUNDS
HYDROLASES
KINETICS
MAMMALS
MAN
NUCLEIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
ORGANIC OXYGEN COMPOUNDS
PHOSPHODIESTERASES
PRIMATES
PYRIMIDINE DIMERS
PYRIMIDINES
RADIATION EFFECTS
RADIATIONS
REACTION KINETICS
RECOVERY
REPAIR
STRUCTURAL CHEMICAL ANALYSIS
ULTRAVIOLET RADIATION
VERTEBRATES