Dynamic pattern of histone H3 core acetylation in human early embryos.

After fertilization, highly differentiated sperm and oocyte are reprogrammed to totipotent embryo, which subsequently cleavages and develops into an individual through spatial-temporal differentiation. Histone modifications play critical roles to coordinate with other reprogramming events in early stages of embryogenesis. However, most of studies focus on modifications at N-terminus of histones, those at nucleosome core were not well understood. Here, we characterize the three key acetylation events in the histone H3 core, H3K56/K64/K122ac, in early human embryos. The three residues localize at DNA entry-exit position of the nucleosome. Globally, H3K56ac, H3K64ac and H3K122ac were detectable throughout preimplantation stages, with H3K64ac levels being relatively stronger and H3K122ac levels being much weaker. Besides, H3K56ac level had a peak at two-cell stage. Moreover, we found that LINEs also peak at two-cell stage, and H3K56ac was enriched at young LINE-1 in human ESCs, supporting that H3K56ac is an important driving force for young LINE-1 activation in human preimplantation embryos. Our results suggest that acetylation in the nucleosome core of histone H3 is dynamic and various during preimplantation development, and may drive diverse chromatin remodeling events in this developmental window.