Has a role in cell differentiation and cell cycling by negatively regulating cig2 and cdc12-associated cdc2. Down-regulates the level of cdc13, particularly in a nitrogen deprived environment. Regulator of cell cycle G1 phase progression. Prevents onset of mitosis during the pre-Start G1 period. Required for degradation of cdc13 mitotic cyclin B during G1 arrest but not during mitotic exit. Phosphorylated by cdc2-cdc13-CDK complex. This targets srw1 for proteolysis which in turn promotes cdc13 turnover. Dephosphorylated during G1 arrest. Belongs to the WD repeat CDC20/Fizzy family.