Required for resistance to the DNA-damaging agents methyl methanesulfonate (MMS), cisplatin and oxaliplatin, but not to mitomycin C. Plays a role in protection against mutation accumulation. May be a component of the recombination-repair pathway. Component of the SHU complex composed of at least CSM2, PSY3, SHU1 and SHU2. Present with 876 molecules/cell in log phase SD medium.