Cells synchronized in G1 progressed through the cell cycle and retained viability until the movement of the nucleus to the neck between the mother cell and the large bud. The duplicated DNA was dispersed along the spindle, extending from mother to daughter cell. The mitotic phenotype is very similar to yeast mutants that are defective in chromosome disjunction. The mutant also showed defects in cytokinesis. Mutational analysis of calmodulin in Saccharomyces cerevisiae.
Several observations indicate that calmodulin is also required for cellular growth and division.
Deletion of the calmodulin gene is a lethal mutation in Saccharomyces cerevisiae, Schizosaccharomyces pombe and Aspergillus nidulans. Expression of calmodulin antisense RNA in mouse C127 cells causes a transient arrest at G1 and metaphase. Although these results indicate calmodulin plays a critical function during proliferation, they do not reveal the function. S. cerevisiae offers an excellent system for identifying calmodulin functions. Because calmodulin mutants can be readily constructed by gene replacement the consequences of mutations in calmodulin can be directly examined in vivo without interference from wild-type calmodulin.