Endonuclease activity in E. coli against photoalkylated DNA
Photoalkylation, the ultraviolet irradiation (wavelength > 305 nm) of DNA in the presence of isopropanol and the free radical photoinitiator di-tert-butylperoxide, causes a variety of base alterations. These include 8-(2-hydroxy-2-propyl)guanine, 8-(2-hydroxy-2-propyl)adenine and thymine dimers. The authors have found a endonuclease activity in E. coli directed against photoalkylated DNA. This activity converts photoalkylated superhelical PM2 phage DNA to the nicked form, as measured by a nitrocellulose filter binding assay. Enzyme activities were compared between crude extracts of mutant strain BW9051 (xth/sup -/), lacking in exonuclease III activity, and strain BW434 (xth/sup -/, nth/sup -/), deficient in both exonuclease III and endonuclease III. The endonuclease level in the double mutant against substrate photoalkylated DNA was under 20% of the activity in the E. coli strain lacking only exonuclease III. This was paralleled by a similar finding of deficient activity in the double mutant against partially depurinated PM2 DNA. Irradiation of the DNA substrate in the absence of isopropanol did not affect the activity in either strain. These studies suggest that the enzyme activity against photoalkylated DNA is endonuclease III and that the substrate photoproduct is neither a 8-(2-hydroxy-2-propyl)purine nor a thymine dimer.
- Research Organization:
- Temple Univ. School of Medicine, Philadelphia, PA
- OSTI ID:
- 5092076
- Report Number(s):
- CONF-8606151-
- Journal Information:
- Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States), Journal Name: Fed. Proc., Fed. Am. Soc. Exp. Biol.; (United States) Vol. 45:6; ISSN FEPRA
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
ADENINES
AMINES
ANTIMETABOLITES
AROMATICS
AZAARENES
BACTERIA
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
DNA
DNA-ASE
DRUGS
ELECTROMAGNETIC RADIATION
ENDONUCLEASES
ENZYME ACTIVITY
ENZYMES
ESCHERICHIA COLI
ESTERASES
GENETIC EFFECTS
GENETIC RADIATION EFFECTS
GUANINE
HETEROCYCLIC COMPOUNDS
HYDROLASES
HYDROXY COMPOUNDS
MICROORGANISMS
NUCLEIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOSPHODIESTERASES
PURINES
RADIATION EFFECTS
RADIATIONS
ULTRAVIOLET RADIATION