Identification of a positive regulator of the cell cycle ubiquitin-conjugating enzyme Cdc34 (Ubc3).
AUTOR(ES)
Prendergast, J A
RESUMO
The Cdc34 (Ubc3) ubiquitin-conjugating enzyme from Saccharomyces cerevisiae plays an essential role in the progression of cells from the G1 to S phase of the cell division cycle. Using a high-copy suppression strategy, we have identified a yeast gene (UBS1) whose elevated expression suppresses the conditional cell cycle defects associated with cdc34 mutations. The UBS1 gene encodes a 32.2-kDa protein of previously unknown function and is identical in sequence to a genomic open reading frame on chromosome II (GenBank accession number Z36034). Several lines of evidence described here indicate that Ubs1 functions as a general positive regulator of Cdc34 activity. First, overexpression of UBS1 suppresses not only the cell proliferation and morphological defects associated with cdc34 mutants but also the inability of cdc34 mutant cells to degrade the general amino acid biosynthesis transcriptional regulator, Gcn4. Second, deletion of the UBS1 gene profoundly accentuates the cell cycle defect when placed in combination with a cdc34 temperature-sensitive allele. Finally, a comparison of the Ubs1 and Cdc34 polypeptide sequences reveals two noncontiguous regions of similarity, which, when projected onto the three-dimensional structure of a ubiquitin-conjugating enzyme, define a single region situated on its surface. While cdc34 mutations corresponding to substitutions outside this region are suppressed by UBS1 overexpression, Ubs1 fails to suppress amino acid substitutions made within this region. Taken together with other findings, the allele specificity exhibited by UBS1 expression suggests that Ubs1 regulates Cdc34 by interaction or modification.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=231047Documentos Relacionados
- Novel CDC34 (UBC3) ubiquitin-conjugating enzyme mutants obtained by charge-to-alanine scanning mutagenesis.
- Intragenic suppression among CDC34 (UBC3) mutations defines a class of ubiquitin-conjugating catalytic domains.
- The Ubc3 (Cdc34) ubiquitin-conjugating enzyme is ubiquitinated and phosphorylated in vivo.
- Identification of a portable determinant of cell cycle function within the carboxyl-terminal domain of the yeast CDC34 (UBC3) ubiquitin conjugating (E2) enzyme.
- Genetic and biochemical interactions between an essential kinetochore protein, Cbf2p/Ndc10p, and the CDC34 ubiquitin-conjugating enzyme.