Role of chromatin structure in zygotic gene activation in the mammalian embryo.

Changes in chromatin structure, rather than changes in the activity of the transcriptional apparatus, may underlie the timing and basis for zygotic gene activation in the mouse embryo. The transcriptional capacity of the male and female pronuclei differs and the first mitosis is associated with development of a transcriptionally repressive state such that efficient gene expression requires a functional enhancer. This repressive state is also relieved by increasing the level of histone H4 hyperacetylation. Zygotic gene activation is also associated with the transient enrichment of chromatin containing hyperacetylated histone H4 and RNA polymerase II at the nuclear periphery. Depletion of maternally-derived histones as the signal for zygotic gene activation is explored.