Global genome removal of thymine glycol in Escherichia coli requires endonuclease III but the persistence of processed repair intermediates rather than thymine glycol correlates with cellular sensitivity to high doses of hydrogen peroxide.

Using a monoclonal antibody that specifically recognizes thymine glycol (Tg) in DNA, we measured the kinetics of the removal of Tg from the genomes of wild-type and repair gene mutant strains of Escherichia coli treated with hydrogen peroxide. Tg is rapidly and efficiently removed from the total genomes of repair-proficient cells in vivo and the removal of Tg is completely dependent on the nth gene that encodes the endonuclease III glycosylase. Hence, it appears that little redundancy in the repair of Tg occurs in vivo, at least under the conditions used here.

Immunofluorescence detection of radiation-induced DNA base damage.

We previously described a sensitive assay for measuring thymine glycol in the DNA of irradiated cells. The assay combines immunorecognition of the DNA lesion with capillary electrophoresis and laser-fluorescence detection to achieve an absolute detection level in the zeptomole (10(-21) mol) range. This article describes modifications to the protocol that overcome certain technical problems seen with the original methodology.