HIST2H3A,histone cluster 2, H3a.It is the core component of nucleosome. 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. DNA accessibility is regulated via a complex set of post-translational modifications of histones, also called histone code, and nucleosome remodeling. HIST2H3A is Expressed during S phase, then expression strongly decreases as cell division slows down during the process of differentiation.