Clb1 is phosphorylated and localizes to the nucleus during metaphase I.

<p>Cultures of <i>CLB1-myc₉</i>, <i>P_CLB2CDC55 CLB1-myc₉</i>, <i>P_CLB2CDC20 CLB1-myc₉</i> and <i>P_CLB2CDC20 P_CLB2CDC55 CLB1-myc₉</i> strains were induced to enter meiosis by transferring them to SPM. A) Modification of Clb1 was assayed by subjecting whole cell extracts from the above cultures to SDS-PAGE followed by Western analysis using an anti-myc antibody. Tubulin served as a loading control. B) Cells were fixed and examined for Clb1-Myc localisation by <i>in situ</i> immunofluorescence. Proportion of cells with nuclear Clb1 (green), cytoplasmic Clb1 (red) and no Clb1 signals (blue) are indicated. A representative image of a cell belonging to each of the three categories is shown below the graphs. C) Clb1 was immunoprecipitated from a culture of <i>P_CLB2CDC20 CLB1-myc₉ cdc28-as</i> cells following 8 hours into SPM and then were either mock treated or incubated with λ-phosphatase alone or with λ-phosphatase + phosphatase inhibitors at 30°C for 30 minutes. Samples were analysed by SDS-PAGE followed by Western blotting. Asterisk indicates a Clb1 cleavage fragment.