Images See all
Histones are the basic nuclear proteins responsible for the nucleosome structure of the chromosomal fiber. Five classes of histone genes have been reported, some of which are expressed only during S phase, while others are replication independent. The latter are referred to as replacement histones and are expressed in quiescent or terminally differentiated cells. [PMID: 8586426] Nucleosomes wrap and compact DNA into chromatin, limiting DNA accessibility to the cellular machineries which require DNA as a template. Histones thereby play a central role in transcription regulation, DNA repair, DNA replication and chromosomal stability. H3F3A is one replacement histone [PMID:16258499].