Involved in bleomycin tolerance with links to DNA repair and/or proteasome function. Monomer. Expression is induced in response to DNA replication stress. Phosphorylated by PKA in vitro. Leads to sensitivity to bleomycin (Ref.7). Bleomycin sensnsitivity is even increased when CUB1 deletion is combined with proteasome mutants including PRE9 or UMP1 disruptions (Ref.7). Suppresses the copper tolerance induced by the proteasome subunit PRE9 disuption (Ref.7). Leads to synthetic sickness with deletion of RAD6 on media containing bleomycin, but not hydroxyurea (HU) (Ref.7). Belongs to the CUB1 family.