sentences:  The nucleosome octamer includes two copies of each histone H2A, H2B, H3, and H4.Due to the tight association of histone proteins to DNA, eukaryotic cells have proteins that are designed to remodel histones ahead of the replication fork, in order to allow smooth progression of the replisome.There are also proteins involved in reassembling histones behind the replication fork to reestablish the nucleosome conformation.