In vivo localisation of fission yeast cyclin-dependent kinase cdc2p and cyclin B cdc13p during mitosis and meiosis.

We investigated the in vivo localisation of fission yeast cyclin-dependent kinase cdc2p during mitosis and meiosis. Fusion to yellow fluorescent protein (YFP) revealed that cdc2-YFP is present in the cytoplasm at all stages of the cell cycle. Nuclear cdc2-YFP fluorescence oscillates with that of cdc13-YFP cyclin. At G1/S, at least one of cdc13p, cig1p or cig2p B-type cyclins is required for the accumulation of cdc2-YFP into the nucleus. Cdc2-YFP and cdc13-YFP are highly enriched on the spindle pole body of cells in late G2 or arrested at S phase. Both accumulate on the spindle pole bodies and the spindle in prophase and metaphase independently of the microtubule-associated protein dis1p. In anaphase, the cdc2p/cdc13p complex leaves the spindle prior to sister chromatid separation, and cdc13-YFP is enriched at the nuclear periphery before fluorescence disappears. If cdc13p cannot be recognized by the anaphase-promoting complex, cdc2-YFP and cdc13-YFP remain associated with the spindle. In mating cells, cdc2-YFP enters the nucleus as soon as the cells undergo fusion. During karyogamy and meiotic prophase, cdc2-YFP is highly enriched on the centromeres. In meiosis I, association of cdc2-YFP with the spindle and the spindle pole bodies shows differences to mitotic cells, suggesting different mechanisms of spindle formation. This study suggests that changes in cdc2p localisation are important for both mitosis and meiosis regulation.