(D) Xenopus sperm chromatin (6 000 sperm heads/µl were incubated with 120 µl of control, Nup50-depleted or egg extracts supplemented with excess (1X = 0.07 µM final) recombinant Xenopus Nup50 and re-purified. Total input extracts were analyzed by western blotting against Nup50 and isolated chromatin were analyzed by western blotting against RCC1 and Histone H3 as a loading control (left panel). The quantification (right panel) shows the mean signal intensity of the RCC1 signal normalized over histone H3 from three independent experiments. Data points from individual experiments are indicated. 