CDK activity is required for Clb1 phosphorylation and nuclear localization during meiosis I.

<p>Cultures of <i>CDC28 P_CLB2CDC20 CLB1-myc₉</i> cells and <i>cdc28-as P_CLB2CDC20 CLB1-myc₉</i> cells were induced to enter meiosis by transferring them to SPM. 1-NM-PP1 (10 µM) was added to the cultures after 5, 6, 7 and 8 hours in SPM. As a control, an equivalent amount of DMSO was added to the cultures after 5 h in SPM. Samples were taken hourly from 5 hours onwards for whole cell extracts and for <i>in situ</i> immunofluorescence. Whole cell extracts were analysed by Western blotting using anti-myc and anti-tubulin antibodies. Localization of Clb1 was assayed by <i>in situ</i> immunofluorescence (green-nuclear, red-cytoplasmic, blue-no signal). Western blotting and Clb1 localization data for the three cultures DMSO/5 h, 1-NM-PP1/5 h and 1-NM-PP1/7 h are indicated in A, B and C respectively. Data for additional time points are indicated in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0079001#pone.0079001.s003" target="_blank">Figure S3</a>.