UBIQUITIN, A CENTRAL COMPONENT OF SELECTIVE CYTOPLASMIC PROTEOLYSIS, IS LINKED TO PROTEINS RESIDING AT THE LOCUS OF NONSELECTIVE PROTEOLYSIS, THE VACUOLE

Ubiquitin, an evolutionary highly conserved protein, is known to be involved in selective proteolysis in the cytoplasm. Here we show that ubiquitin-protein conjugates are also found in the yeast vacuole. Mutants defective in the major vacuolar endopeptidases, proteinase yscA and yscB, lead to accumulation of ubiquitin-protein conjugates in this cellular organelle.