The CBK1 gene of Saccharomyces cerevisiae encodes a protein kinase that is a member of the NDR (Nuclear Dbf2 Related) family of protein kinases, which are involved in morphogenesis and cell proliferation. Previous studies have shown that deletion of CBK1 leads to a loss of polarity and the formation of large aggregates of cells. This aggregation phenotype is due to the loss of the daughter cell specific accumulation of the transcription factor Ace2p, which is responsible for the transcription of genes whose products are necessary for the final separation of the mother and daughter at the end of cell division. We show that the daughter cell specific localization of Ace2p does not occur via a specific localization of the ACE2 mRNA, and that in vivo, the transcription of CTS1, one of the principal targets of Ace2p, is daughter cell specific. We have shown that extragenic suppressors of the Deltacbk1 aggregation phenotype are located in the nuclear exportin CRM1 and ACE2. These mutations disrupt the interaction of Ace2p and Crm1p, thus impairing Ace2p export and resulting in the accumulation of the protein in both mother and daughter cell nuclei. We propose that in the daughter cell nucleus Cbk1p phosphorylates the Ace2p nuclear export signal, and that this phosphorylation blocks the export of Ace2p via Crm1p, thus promoting the daughter cell specific nuclear accumulation of Ace2p.
|Evidence ID||Analyze ID||Interactor||Interactor Systematic Name||Interactor||Interactor Systematic Name||Type||Assay||Annotation||Action||Modification||Phenotype||Source||Reference||Note|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Gene Ontology Term||Gene Ontology Term ID||Qualifier||Aspect||Method||Evidence||Source||Assigned On||Annotation Extension||Reference|
|Evidence ID||Analyze ID||Gene||Gene Systematic Name||Phenotype||Experiment Type||Experiment Type Category||Mutant Information||Strain Background||Chemical||Details||Reference|
|Evidence ID||Analyze ID||Regulator||Regulator Systematic Name||Target||Target Systematic Name||Experiment||Assay||Construct||Conditions||Strain Background||Reference|