Alexander Y. Amerik, Shyr-Jiann Li, Mark Hochstrasser
Analysis of the Deubiquitinating Enzymes of the Yeast Saccharomyces cerevisiae
Attachment of proteins to ubiquitin is reversed by
specialized proteases called deubiquitinating enzymes
(Dubs), which are also essential for ubiquitin
precursor processing. In the genome of Saccharomyces
cerevisiae, 17 potential DUB genes can be discerned.
We have now constructed strains deleted for
each of these genes. Surprisingly, given the essential
nature of the ubiquitin system, none of the mutants is
lethal or strongly growth defective under standard
conditions, although a number have detectable abnormalities.
Including results from this study, 14 of the
17 Dubs have now been shown to have ubiquitin-cleaving
activity. The most extensively characterized
yeast Dub is Doa4, which is required for both ubiquitin
homeostasis and proteasome-dependent proteolysis.
To help determine what distinguishes Doa4 functionally
from other Dubs, we have cloned a DOA4 ortholog
from the yeast Kluyveromyces lactis. The K. lactis
protein is 42% identical to Doa4, but unexpectedly the
K. lactis gene is slightly closer in nucleotide sequence
to UBP5, which cannot substitute for DOA4 even in
high dosage. The data suggest that the DOA4 locus
underwent a duplication after the divergence of K. lactis
and S. cerevisiae. This information will facilitate
fine-structure analysis of the Doa4 protein to help delineate
its key functional elements.
Biological Chemistry, Walter de Gruyter
Print ISSN: 1431-6730
Volume: 381, 09/2000
Pages: 981 - 992
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