FUNCTIONAL DOMAINS FOR ASSEMBLY OF HISTONES H3 AND H4 INTO THE CHROMATIN OF XENOPUS EMBRYOS

Histones H3 and H4 have a well defined structural role in the nucleoso me and an established role in the regulation of transcription. We have made use of a microinjection strategy using Xenopus embryos to define the minimal structural components of H3 and H4 necessary for nucleoso me assembly into metazoan chromosomes in vivo. we find that both the N -terminal tail of H4, including all sites of acetylation, and the C-te rminal alpha-helix of the H4 histone fold domain are dispensable for c hromatin assembly. The N-terminal tail and an N-terminal alpha-helix o f H3 are also dispensable for chromatin assembly. However, the remaind er of the H3 and H4 histone folds are essential for incorporation of t hese proteins into chromatin. We suggest that elements of the histone fold domain maintain both nucleosomal integrity and have distinct func tions essential for cell viability.