Cbk1p, a protein similar to the human myotonic dystrophy kinase, is essential for normal morphogenesis in Saccharomyces cerevisiae

We have studied the CBK1 gene of Saccharomyces cerevisiae, which encodes a conserved protein kinase similar to the human myotonic dystrophy kinase. We have shown that the subcellular localization of the protein, Cbk1p, varies in a cell cycle-dependent manner. Three phenotypes are associated with the inactivation of the CBK1 gene: large aggregates of cells, round rather tha n ellipsoidal cells and a change from a bipolar to a random budding pattern . Two-hybrid and extragenic suppressor studies have linked Cbk1p with the t ranscription factor Ace2p, which is responsible for the transcription of ch itinase. Cbk1p is necessary for the activation of Ace2p and we have shown t hat the aggregation phenotype is due to a lack of chitinase expression. The random budding pattern and the round cell phenotype of the CBK1 deletion s train show that in addition to its role in regulating chitinase expression via Ace2p, Cbk1p is essential for a wild-type morphological development of the cell.