Histone chaperones: Variety and functions

Histone chaperones are required for the formation of the nucleosome—the basic unit of chromatin that consists of the DNA and histones. In this review, participation of histone chaperones CAF-1, ASF1, NAP1, and FACT in key cellular processes is discussed. Being multifunctional factors, histone chaperones take part in DNA replication, transcription, and repair. During replication, histone chaperones are required to form chromatin structure on both the mother and daughter DNA. They are involved at different stages of genome packaging: from histone transport into the nucleus to nucleosome formation. During transcription, histone chaperones reduce a nucleosome barrier for RNA polymerases accelerating the rate of RNA synthesis and promote nucleosome reassembly. During DNA repair, histone chaperones provide access to the damaged genome region for the repair enzymes, and participate in the chromatin assembly after DNA repair. Mutations in histone chaperones typically result in multiple defects in the cell, underlying the functional importance of these proteins.