PHOSPHOINOSITIDE-SPECIFIC PHOSPHOLIPASE-C FORMS A COMPLEX WITH 14-3-3-PROTEIN AND IS INVOLVED IN EXPRESSION OF UV RESISTANCE IN FISSION YEAST

The fission yeast plc1(+) gene encodes phosphoinositide-specific phosp holipase C. The two-hybrid interaction assay with plexA-plc1(+) as a b ait revealed that Plc1p interacted with the 14-3-3 proteins Rad24p and Rad25p. Formation of a complex containing Plc1p and Rad24p in vivo wa s confirmed by an immunological method. As predicted from the fact tha t rad24 null mutant cells are hypersensitive to UV irradiation, plc1 n ull mutant cells were almost as sensitive to UV irradiation as, rad24 null mutant cells. In addition, deletion of rad24 in the plc1 null mut ant cells did not enhance the UV sensitivity, indicating that plc1(+) and rad24(+) belong to the same epistasis group with respect to UV sen sitivity. Whereas Rad24p has been reported to be involved in the DNA d amage checkpoint pathway, the delay to mitosis after UV irradiation wa s not defective either in rad24 null mutant cells or in plc1 null muta nt cells in our analysis. Thus, Plc1p is responsible for resistance to UV irradiation, but not for the DNA damage checkpoint pathway, in coo peration with 14-3-3 proteins.