Histone Variants and Epigenetics

SUMMARY Histones package and compact DNA by assembling into nucleosome core particles. Most histones are synthesized at S phase for rapid deposition behind replication forks. In addition, the replacement of histones deposited during S phase by variantsthat can be deposited independentlyof replication provide the most fundamental level of chromatin differentiation. Alternative mechanisms for depositing different variants can potentiallyestablish and maintain epigenetic states. Variants have also evolved crucial roles in chromosome segregation, transcriptional regulation, DNA repair, and other processes. Investigations into the evolution, structure, and metabolism of histone variants provide a foundation for understanding the participation of chromatin in important cellular processes and in epigenetic memory.