A histone programme during the life cycle of the sea urchin

The histone complement of chromatin from early gastrula, late gastrula and from fully differentiated gut cells of the sea urchin Parechinus angulosus has been fractionated by molecular sieve and ion-exchange chromatography. Several of the subfractions thus isolated have been characterized by amino acid composition and partial amino acid sequences as a series of variants of the histones H1, H2A and H2B. Specific histone variants are present in chromatin at specific stages of differentiation.