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

Journal Article · Tue Aug 07 00:00:00 EDT 1990 · Biochemistry; (USA)

DOI:https://doi.org/10.1021/bi00483a009· OSTI ID:6097170

Ganguly, Tapan; Weems, K M; Duker, N J ^[1]

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1. Temple Univ. School of Medicine, Philadelphia, PA (USA)

Ultraviolet irradiation of DNA results in various pyrimidine modifications. The authors 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-({sup 3}H)dT){center dot}poly(dA-({sup 3}H)dT) was UV irradiated and incubated with purified E. coli endonuclease III. {sup 3}H-Containing material was released in a manner consistent with Michaelis-Menten kinetics. This {sup 3}H-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 {sup 3}H-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 repairability of these thymine hydrates suggests that they are stable in DNA and therefore potentially genotoxic.

• OSTI ID: 6097170
• Journal Information: Biochemistry; (USA), Journal Name: Biochemistry; (USA) Vol. 29:31; ISSN 0006-2960; ISSN BICHA
• Country of Publication: United States
• Language: English

Related Subjects

560120* -- Radiation Effects on Biochemicals
Cells
& Tissue Culture
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AZINES
BACTERIA
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
DNA
DNA REPAIR
DNA-ASE
ELECTROMAGNETIC RADIATION
ENDONUCLEASES
ENZYME ACTIVITY
ENZYMES
ESCHERICHIA COLI
ESTERASES
EXCISION REPAIR
GLYCOSYL HYDROLASES
HETEROCYCLIC COMPOUNDS
HYDRATES
HYDROGEN COMPOUNDS
HYDROLASES
HYDROXY COMPOUNDS
MICROORGANISMS
NUCLEIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOSPHODIESTERASES
PYRIMIDINE DIMERS
PYRIMIDINES
RADIATION EFFECTS
RADIATIONS
RECOVERY
REPAIR
THYMINE
TRITIUM COMPOUNDS
ULTRAVIOLET RADIATION
URACILS