Separate SCFCDC4 recognition elements target Cdc6 for proteolysis in S phase and mitosis

Publisher Website
Google Scholar
Abstract
The Cdc6 DNA replication initiation factor is targeted for ubiquitin‐mediated proteolysis by the E3 ubiquitin ligase SCFCDC4 from the end of G1 phase until mitosis in the budding yeast Saccharomyces cerevisiae . Here we describe a dominant‐negative CDC6 mutant that, when overexpressed, arrests the cell cycle by inhibiting cyclin‐dependent kinases (CDKs) and, thus, prevents passage through mitosis. This mutant protein inhibits CDKs more efficiently than wild‐type Cdc6, in part because it is completely refractory to SCFCDC4‐mediated proteolysis late in the cell cycle and consequently accumulates to high levels. The mutation responsible for this phenotype destroys a putative CDK phosphorylation site near the middle of the Cdc6 primary amino acid sequence. We show that this site lies within a novel Cdc4‐interacting domain distinct from a Cdc4‐interacting site identified previously near the N‐terminus of the protein. We show that both sites can target Cdc6 for proteolysis in late G1/early S phase whilst only the newly identified site can target Cdc6 for proteolysis during mitosis.