Histone H3.3 (H3-3A)

Variant histone H3 which replaces conventional H3 in a broad assortment of nucleosomes in active genes. Constitutes the predominant form of histone H3 in non-dividing cells and is incorporated into chromatin independently of DNA synthesis.

Deposited at websites of nucleosomal displacement throughout transcribed genes, suggesting that it represents an epigenetic imprint of transcriptionally active chromatin. Nucleosomes wrap and compact DNA into chromatin, restricting DNA accessibility to the cellular machineries which require DNA as a template.