Bk. Baxter et Ea. Craig, ISOLATION OF UBP3, ENCODING A DE-UBIQUITINATING ENZYME, AS A MULTICOPY SUPPRESSOR OF A HEAT-SHOCK MUTANT STRAIN OF SACCHAROMYCES-CEREVISIAE, Current genetics, 33(6), 1998, pp. 412-419
Yeast strains lacking functional copies of the two genes SSA1 and SSA2
, which encode cytosolic molecular chaperones, are temperature-sensiti
ve. In this report, we describe the isolation of a high-copy suppresso
r of this temperature sensitivity, UBP3, which encodes a de-ubiquitina
ting enzyme. We show that ubp3 mutant yeast strains have a mild slow-g
rowth phenotype and accumulate ubiquitin-protein conjugates. We propos
e a model in which Ubp3p acts in vivo to reverse the ubiquitination of
substrate proteins, allowing temporarily misfolded proteins an opport
unity to fold correctly.