The function of the chicken p34CDC2 protein kinase in fission yeast is cold sensitive for cell cycle progression through the G1 phase and temperature sensitive for traversal of mitosis.

The protein kinase p34cdc2 is required at the onset of DNA replication and for entry into mitosis. The catalytic subunit and its regulatory proteins, notably the cyclins, are conserved from yeast to man. This suggests that the control mechanisms necessary for progression through the cell cycle in fission yeast are conserved throughout evolution. This work describes the characterization of a fission yeast strain that is dependent for cell cycle progression on the activity of the p34CDC2 protein kinase from chicken. The response of the chicken p34CDC2 protein kinase to cell cycle components of fission yeast was examined. Cells expressing the chicken p34CDC2 protein divide at reduced size at 31 degrees C. Cells are temperature sensitive at 35.5 degrees C and die as a result of mitotic catastrophe. This phenotype can be rescued by delaying cell cycle progression at the G1-S transition by adding low concentrations of hydroxyurea. Schizosaccharomyces pombe cells that are dependent on chicken p34CDC2 are cold sensitive. At 19 degrees C to 25 degrees C cells arrest in the G1 phase, while traversal of the G2-M transition is not blocked at low temperature. Expression of chicken p34CDC2 in the cold-sensitive G2-M mutant cdc2A21 suppresses the G1 arrest.