LAUSR

The bZIP transcription factor Atf1 is a key player in the transcriptional programme of Schizosaccharomyces pombe cell cycle. It also controls both expression and degradation of mitotic cyclin Cdc13. Temporal regulation of these opposing functions of Atf1 is critical for fidelity of cell division. Our investigations revealed that an increase in the activity of mitogen‐activated protein kinase (MAPK) Spc1 during mitotic exit and the consequent phosphorylation of Atf1 along with the prevailing high activity of cyclin‐dependent kinase Cdc2 regulate Cdc13 degradation. Our results also indicate the possibility of a complex interplay between Cdc2 inhibitory kinase Wee1, the anaphase‐promoting complex and Atf1 during mitotic exit. These observations provide evidence of new regulatory mechanisms of mitotic exit.