Histone synthesis in preimplantation mouse embryos.

The synthesis of histones by preimplantation mouse embryos was examined by electrophoresis of [3H]-lysine-labeled acid extracts of cleavage stage embryos. Histones were synthesized by fertilized zygotes, two-cell, eight-cell, and morula stage embryos. Their identity was confirmed by coextraction and coelectrophoresis in a number of systems and differential labeling with [3H]-tryptophan. There was evidence of post-translational modifications of the embryonic histones. The estimated histone synthetic rate was sufficient to provide the chromatin requirements of cleavage division as related to DNA synthesis. The results are discussed in relation to coordination of histone and DNA synthesis in the preimplantation embryo.