UMP1 is a short-lived chaperone present in the precursor form of the 20S proteasome and absent in the mature complex. UMP1 is required for the correct assembly and enzymatic activation of the proteasome. UMP1 seems to be degraded by the proteasome upon its formation

1: Ump1p is required for proper maturation of the 20S proteasome and becomes its substrate upon completion of the assembly. Ramos PC, Hockendorff J, Johnson ES, Varshavsky A, Dohmen RJ; Cell 1998;92:489-499. PMID:9491890