Fig. 1.

Depletion of Aur-A delays mitotic entry, but does not block it. (A) Cycling extracts were prepared 30 min after egg activation and immunodepleted with two rounds of IgG (mock) or affinity-purified Aur-A antibody. Samples were analyzed by SDS/PAGE followed by blotting with Aur-A and cdc2 antibodies. (B) Mock or Aur-A-depleted cycling extracts were supplemented with demembranated sperm nuclei (500 per μl). Samples were stained with Hoechst dye 33342 and visualized by fluorescence microscopy. At least 100 chromosome structures at each time point were quantified. (C) Representative chromatin structures from B. (D) Samples were analyzed by SDS/PAGE followed by blotting with indicated antibodies. Cdc2 activity toward histone H1 was assayed by incorporation of γ-³²P, followed by SDS/PAGE and autoradiography. (E) Cycling extracts lacking sperm nuclei were mock- or Aur-A-depleted. Samples were blotted with the indicated antibodies.