CHROMATIN TRANSITIONS DURING EARLY XENOPUS EMBRYOGENESIS - CHANGES IN HISTONE-H4 ACETYLATION AND IN LINKER HISTONE TYPE

We describe major transitions in the type and modification of chromatin-associated proteins daring the early development of Xenopus laevis. Histone H4 is stored in the diacetylated form in the egg and is progressively deacetylated during normal development. If histone deacetylases are inhibited with sodium butyrate, hyperacetylated histone H4 only accumulates after the mid-hlastula transition. The type of linker histone in chromatin also changes during embryogenesis, from predominantly the B4 protein at the mid-blastula transition to predominantly histone HI at the end of gastrulation. These transitions in chromatin composition correlate with major changes in the replicative and transcriptional activity of embryonic nuclei. © 1993 by Academic Press, Inc.