A CDC2-LIKE KINASE ASSOCIATED WITH COMMITMENT TO DIVISION IN PARAMECIUM-TETRAURELIA

Cell division in higher eukaryotes is mainly controlled by p34(cdc2) o r related kinases and by other components of these kinase complexes. W e present evidence that cdc2-like kinases also occur in Paramecium. Tw o polypeptides reacted with an antibody directed against the perfectly conserved PSTAIR region found in cdc2 kinases in other eukaryotes. On ly the less abundant peptide bound to p13(sucl) from Schizosaccharomyc es pombe. Using centrifugal elutriation to select cells on the basis o f size, we isolated highly synchronous Paramecium G1 cells. With this procedure, we demonstrated that the p13(sucl)-associated cdc2-like his tone H1 kinase was activated before cell division at the point of comm itment to division in Paramecium. Further, we show that Paramecium cdc 2-like proteins occurred principally as monomers and that these monome rs were active as histone H1 kinases in vitro.