PMC

An in vitro centriole separation assay. Deconvolution images of centriole doublets and singlets. (A and A′) These doublets represent the 0-h starting point of the assay. (B and B′) At the 1-h endpoint, the majority of centrosomes are singlets, as depicted. (A and B) α-Tubulin staining. (A′ and B′) γ-Tubulin staining. (Bar = 1 μm.)

The dependence of centriole separation on cyclin-dependent kinases. The graphs express centriole separation activity as conversion percentages, as described in Table . (A) Depletion and rescue of centriole separation activity with Suc1p and cyclin E/cdk2. (B) Depletion of both cyclin E- and cyclin A-dependent kinases inhibits centriole separation. The conversion percentage has been normalized to the control depletion (uncoupled protein A-Sepharose). (C) The mitotic state inhibits centriole separation.

The cdk inhibitor p21 blocks centrosome duplication in frog embryos. Embryonic cells were injected with various inhibitors and treated with cycloheximide for 4 h to allow for centrosome overduplication. Asterisks mark the injected cells, as visualized by coinjection of a fluorescein-conjugated dextran. (A) p21. (B and B′) p21 and cyclin E (two different sections are shown to view all centrosomes). (C) p21 N terminus. (D) p21 C terminus. (A) γ-Tubulin staining. (B, B′, C, and D) α-Tubulin staining. The difference in cell size is because of the variation in cell stage at the time of injection. (Bar = 100 μm.)