Aspartic-type endopeptidase and ubiquilin; involved in cleavage of long-chain polyubiquitinated substrates; role in ubiquitin (Ub)-dependent, proteasome-independent proteolysis and DNA-protein crosslink repair; Ub-shuttle receptor for HO and Ufo1p; DNA damage-inducible v-SNARE binding protein that may inhibit constitutive exocytosis; possible role in the checkpoint signaling; UBL-UBA family member containing Ub-like (UBL), helical, Ub-associated (UBA) and retroviral-like proteinase domains