As demonstrated in the studies with Xenopus egg cycling extracts described earlier (see Figure 13-7), a decrease in mitotic cyclins and the associated inactivation of MPF coincides with the later stages of mitosis (late anaphase and telophase). Just before this, in early anaphase, sister chromatids separate and move to opposite spindle poles. During telophase, microtubule dynamics return to interphase conditions, the chromosomes decondense, the nuclear envelope reforms, the endoplasmic reticulum and Golgi complex are remodeled, and cytokinesis occurs. Some of these processes are triggered by dephosphorylation; others, by protein degradation.
In this section, we discuss the molecular mechanisms and specific proteins associated with some of the events that characterize early and late mitosis.