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. Author manuscript; available in PMC: 2010 Oct 5.
Published in final edited form as: J Cell Physiol. 2008 Dec;217(3):626–631. doi: 10.1002/jcp.21531

Figure 4.

Figure 4

Cyclin E protein levels remain constant during S phase and G1-like arrest. Sea urchin eggs or zygotes were treated with protein synthesis inhibitors and arrested in first S phase (A) or in a G1-like state (B). Extracts were prepared at one hour intervals. Proteins were separated on a 12% SDS-polyacrylamide gel, transferred to nitrocellulose, and probed with a polyclonal antibody to sea urchin cyclin E. Some proteolysis of cyclin E (full-length 50 kD) to a 36 kD fragment occurs during extract preparation. E = unfertilized eggs; EA/E = unfertilized eggs treated with anisomycin/emetine for 30 minutes; Z = zygotes at 60 minutes after fertilization when inhibition of protein synthesis begins. The densities of cyclin E bands (both 50 kD and 36 kD) from three independent experiments were measured and normalized to the unfertilized egg. For every time point, the mean ± S.E.M. was plotted and the trendline was determined using linear regression (C).