plo1(+) regulates gene transcription at the M–G(1) interval during the fission yeast mitotic cell cycle

The regulation of gene expression plays an important part in cell cycle controls. We describe the molecular machinery that co-ordinates gene transcription at the M–G(1) interval during the fission yeast mitotic cell cycle. A sequence is identified in the cdc15(+) promoter that we call a PCB (pombe cell cycle box), which confers M–G(1)-specific transcription. Sequences similar to the PCB are present in the promoters of seven other genes, spo12(+), cdc19(+), fin1(+), sid2(+), ppb1(+), mid1(+)/dmf1(+) and plo1(+), which we find to be transcribed at M–G(1). A transcription factor complex is identified that binds to the PCB sequence, which we name PBF, for PCB-binding factor. Finally, we show that PBF binding activity and consequent gene transcription are regulated by the Plo1p protein kinase, thus invoking a potential auto-feedback loop mechanism that regulates mitotic gene transcription and passage through septation and cytokinesis.