Nucleoside diphosphokinase, an enzyme with step changes in activity during the cell cycle of the fission yeast Schizosaccharomyces pombe. II. Dissociation of the steps from the DNA-division cycle after induction synchronization.

Synchrony was induced in cultures of the mitotic mutant cdc2.33 of Schizosaccharomyces pombe by shifting up an asynchronous culture to the restrictive temperature for a period of 3.5-4.5 h and then shifting down to the permissive temperature. The resulting synchronous divisions had short cycle times, down to 50% of the normal cycle. The oscillatory control of nucleoside diphosphokinase activity was also synchronized by the shift-down and the activity rose in a step pattern. Unlike the situation in the normal cycle, this step pattern was dissociated from the shortened cell cycle and had a longer period and different phase relations. It may be that the normal entrainment or coupling between the cell cycle and the activity control fails if the cell cycle is too short. The period of the activity control (equal to the protein doubling time at the restrictive temperature) appears to be temperature-compensated.