Quantitative characterization of pyrimidine dimer excision from UV‐irradiated DNA (excision capacity) by cell‐free extracts of the yeast Saccharomyces cerevisiae

Abstract

Cell-free extracts from wild-type yeast @AD+) and from rad mutants belonging to the R4D3 epistatic group (radl-1, rad2-1, rad3-1, rad4-1) contain activities catalyzing the excision of pyrimidine dimers (PD) from purified ultraviolet-irradiated DNA which was not pre-treated with exogenous UV-endonuclease. The level of these activities in cell-free extracts from rad mutants did not differ from that in wild-type extract and was close to the in vivo excision capacity of the latter calculated from the LDH (about lo4 PD per haploid genome).

Deoxyribonucleic acid repair in the yeast Saccharomyces cerevisiae.

“…The authors concluded that the radl, rad2, rad3, rad4, radlO, and radl6 mutants were not defective in the incision of UV-irradiated DNA, but suggested that the defect in these mutants might be at the level of postincisional excision events. Consistent with this interpretation, they subsequently reported that extracts of both wild-type and rcad mutant cells catalyzed the complete excision of pyrimidine dimers from UV-irradiated DNA in vitro (14). Remarkably, in both studies DNA was incubated with cell extracts in the presence of ethylenediaminetetraacetate, suggesting no requirement for divalent cation in the incision or excision reaction(s).…”

The Molecular Genetics of the Incision Step in the DNA Excision Repair Process

“…Although one set of studies reported such an incising ability with cell-free extracts from wild-type cells, such an activity was also shown for the five most sensitive mutant strains (Bekker et al . 1980(Bekker et al . , 1984 .…”