Ultraviolet-induced thymine hydrates in DNA are excised by bacterial and human DNA glycosylase activities

Ultraviolet irradiation of DNA results in various pyrimidine modifications. We studied the excision of an ultraviolet thymine photoproduct by Escherichia coli endonuclease III and by a preparation of human WI-38 cells. These enzymes cleave UV-irradiated DNA at apyrimidinic sites formed by glycosylic...

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Bibliographic Details
Published in:Biochemistry (Easton) 1990-08, Vol.29 (31), p.7222-7228
Main Authors: Ganguly, Tapan, Weems, Kim M, Duker, Nahum J
Format: Article
Language:English
Subjects:
560120 - Radiation Effects on Biochemicals, Cells, & Tissue Culture
AZINES
BACTERIA
Bacterial Proteins - metabolism
Biological and medical sciences
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
Cells, Cultured
Deoxyribonuclease (Pyrimidine Dimer)
DNA
DNA Damage
DNA Glycosylases
DNA REPAIR
DNA-ASE
ELECTROMAGNETIC RADIATION
Endodeoxyribonucleases - metabolism
ENDONUCLEASES
ENZYME ACTIVITY
ENZYMES
ESCHERICHIA COLI
Escherichia coli - enzymology
Escherichia coli Proteins
ESTERASES
EXCISION REPAIR
Fibroblasts - enzymology
Fundamental and applied biological sciences. Psychology
GLYCOSYL HYDROLASES
HETEROCYCLIC COMPOUNDS
Humans
HYDRATES
HYDROGEN COMPOUNDS
HYDROLASES
HYDROXY COMPOUNDS
MICROORGANISMS
Molecular and cellular biology
Molecular genetics
Mutagenesis. Repair
N-Glycosyl Hydrolases - metabolism
NUCLEIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOSPHODIESTERASES
Poly dA-dT - metabolism
Poly dA-dT - radiation effects
PYRIMIDINE DIMERS
PYRIMIDINES
RADIATION EFFECTS
RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT
RADIATIONS
RECOVERY
REPAIR
THYMINE
Thymine - analogs & derivatives
Thymine - metabolism
TRITIUM COMPOUNDS
ULTRAVIOLET RADIATION
Ultraviolet Rays
URACILS
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Summary:Ultraviolet irradiation of DNA results in various pyrimidine modifications. We studied the excision of an ultraviolet thymine photoproduct by Escherichia coli endonuclease III and by a preparation of human WI-38 cells. These enzymes cleave UV-irradiated DNA at apyrimidinic sites formed by glycosylic removal of the photoproduct. Poly(dA-[3H]dT).poly(dA-[3H]dT) was UV irradiated and incubated with purified E. coli endonuclease III. 3H-Containing material was released in a manner consistent with Michaelis-Menten kinetics. This 3H-labeled material was determined to be a mixture of thymine hydrates (6-hydroxy-5,6-dihydrothymine), separable from unmodified thymine by chromatography in three independent systems. Both cis-thymine hydrate and trans-thymine hydrate were chemically and photochemically synthesized. These coeluted with the enzyme-released 3H-containing material. No thymine glycol was released from the UV-irradiated polymer. Similar results were obtained with extracts of WI-38 cells as the enzyme source. The release of thymine hydrates by both glycosylase activities was directly proportional to the amount of enzyme and the irradiation dose to the DNA substrate. These results demonstrate the modified thymine residues recognized and excised by endonuclease III and the human enzyme to be a mixture of cis-thymine hydrate and trans-thymine hydrate. The reparability of these thymine hydrates suggests that they are stable in DNA and therefore potentially genotoxic.
ISSN:0006-2960
1520-4995
DOI:10.1021/bi00483a009