Enhanced UV sensitivity of yeast cells induced by overexpression of Mg(2+)-dependent protein phosphatase alpha (type 2C alpha).

The UV sensitivity of wild-type Saccharomyces cerevisiae cells was increased 2-fold when rat Mg(2+)-dependent protein phosphatase alpha (protein phosphatase type 2C alpha) was overexpressed in the cells. The overexpression of this enzyme rendered the rad 18 mutant (defective in postreplication repair) more UV-sensitive than was observed in the wild-type cells. However, this increase in UV sensitivity disappeared when the host cells had a rad 1 mutation (defective in excision repair). These results suggest that the Mg(2+)-dependent protein phosphatase overexpressed in the yeast cells inhibited their excision repair system.