Functions as a proteasomal ubiquitin receptor. Recruits the deubiquitinating enzyme uchl5 at the 26S proteasome and promotes its activity (By similarity). Plays a role in the transition from growth to differentiation (PubMed:16987957). Interacts with the 26S proteasome (By similarity). Interacts with phg2 (PubMed:16987957). Belongs to the ADRM1 family. The gene for this protein is duplicated in strains AX3 and AX4. These strains contain a duplication of a segment of 750 kb of chromosome 2 compared to the corresponding sequence in strain AX2.