Skip to main content
. 1999 Apr 27;96(9):4797–4802. doi: 10.1073/pnas.96.9.4797

Figure 4.

Figure 4

Effects of AP and compound matrix treatment on spindle assembly reactions in Xenopus egg extracts and reconstitution experiment. (Bar = 10 μm.) The measured histone H1 kinase activity in pmol per min per μl for each reaction is shown in the upper right corner of each part. (A) Control reaction containing demembranated sperm nuclei yields bipolar spindles and high histone H1 kinase activity characteristic of mitotic extracts. (B) In the presence of 200 μM AP, 100% of sperm nuclei decondense and microtubules grow long, with low histone H1 kinase activity characteristic of interphase extracts. (C) Extract treated with C-matrix still yields bipolar spindles and normal kinase activity levels. (D) Extract treated with P-matrix causes interphasic morphology and histone H1 kinase activity similar to treatment with the free compound. (E) Extract treated with P-matrix is rescued by the addition of pure CDK1–cyclin B, yielding bipolar spindles and higher histone H1 kinase activity. (F) Quantification of a representative rescue experiment. One hundred nuclei were counted for each condition. C-matrix treatment yielded nearly 100% mitotic figures, whereas P-matrix treatment resulted in 100% interphase nuclei. Addition of pure CDK1–cyclin B kinase (0.1 vol of 93 pmol per min per μl) to P-matrix-treated extract resulted in 70% of the sperm nuclei forming mitotic figures.