Sperm nuclear chromatin transformations in somatic cell-free extracts.

HeLa cell extracts induced decondensation of lysolecithin permeabilized Xenopus, pig, and human sperm chromatin; decondensation began almost immediately on incubation in the extract and was completed within 10-20 min. The average enlargements of human and pig sperm nuclei were 15-fold and 3-fold, respectively. The structural organization of pig and human sperm chromatin was significantly different. Decondensation was differentially inhibited by Mg++ and polyamines; inhibition was least for Xenopus and most for pig sperm nuclei. The nuclear membrane was disintegrated on chromatin dispersion, whereas the nuclei which failed to decondense exhibited distinct nuclear envelopes. The decondensing factors were stable at 65 degrees C for 15 min. The dispersed chromatin was remodelled to somatic nucleosomal structures within 60 min. The remodelled chromatin could be recondensed to chromosome-like structures, when incubated further in extracts from mitosis arrested HeLa cells.