The effects of dark holding and photoreactivation on ultraviolet light-induced mitotic recombination and survival in yeast.

Abstract

UV induces lesions in DNA which lead to the death of cells, mutation and, in yeast, intragenic and intergenic mitotic recombination. We have investigated the interaction of two post-treatments, dark holding and photoreactivation, on the frequencies of these events. It was found that dark holding reduces cell death and intergenic recombinants, but causes an increase in intragenic recombination frequency. Photoreactivation reduces cell death and intragenic recombination, but has no effect on intergenic recombination. After dark holding, photoreactivation has no further effect on cell survival or intergenic recombination, but may reduce the frequency of intragenic recombinants. After photoreactivation, dark holding still causes an increase in cell survival and the frequency of intragenic recombination, and reduces the frequency of intergenic recombination.