Functionally Distinct Isoforms of Cik1 Are Differentially Regulated by APC/C-Mediated Proteolysis

摘要: Cik1, in association with the kinesin Kar3, controls both mitotic spindle and nuclear fusion during mating. Here, we show that there are two Cik1 isoforms, form includes an N-terminal domain required for ubiquitination by Anaphase-Promoting Complex/Cyclosome (APC/C). During vegetative growth, is expressed mitosis regulates spindle, allowing accurate chromosome segregation. After mitosis, APC/C Cdh1 targets ubiquitin-mediated proteolysis. Upon exposure to mating pheromone α factor, a smaller APC/C-resistant isoform from alternate transcriptional start site. This shorter stable cannot be ubiquitinated . Moreover, isoforms functionally distinct. Cells express only long have defects fusion, whereas cells expressing short increased rate of loss. These results demonstrate coupling regulation APC/C-mediated