Variant histone H3 which replaces conventional H3 in a wide range 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 sites of nucleosomal displacement throughout transcribed genes, suggesting that it represents an epigenetic imprint of transcriptionally active chromatin. 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. The nucleosome is a histone octamer containing two molecules each of H2A, H2B, H3 and H4 assembled in one H3-H4 heterotetramer and two H2A-H2B heterodimers. The octamer wraps approximately 147 bp of DNA. Acetylation is generally linked to gene activation. Can be acetylated to form H3K9ac, H3K14ac, H3K18ac and H3K23ac. H3K9ac could compete with H3K9me and prevent gene silencing. H3K9ac is restricted to euchromatin (By similarity). H3K9ac and H3K14ac are associated with chromatin during interphase. Deacetylation at the metaphase-anaphase transition and maintained up to telophase. Methylated to form mainly H3K4me, H3K9me, H3K18me, H3K23me, H3K27me and H3K36me. H3K4me1/2/3, H3K9me3, H3K27me3 and H3K36me1/2/3 are typical marks for euchromatin, whereas heterochromatic chromocenters are enriched in H3K9me1/2 and H3K27me1/2. H2BK143ub1 is probably prerequisite for H3K4me (By similarity). H3K4me2 and H3K9me2 remain associated with chromosomes during interphase and mitosis. Methylated in vitro by SET1 to form H3K9me and H3K27me. Phosphorylated to form H3T3ph, H3S10ph, H3T11ph and H3S28ph. H3S10ph and H3S28ph found from prophase to telophase. Restricted to chromocenters from prophase to early anaphase, but widespread along chromosomes at late stages of mitosis, when H3 is deacetylated. No phosphorylation detected during interphase. H3S28ph specifically formed by AUR3 while H3T3ph and H3T11ph are not produced by Aurora. Belongs to the histone H3 family. To ensure consistency between histone entries, we follow the 'Brno' nomenclature for histone modifications, with positions referring to those used in the literature for the 'closest' model organism. Due to slight variations in histone sequences between organisms and to the presence of initiator methionine in UniProtKB/Swiss-Prot sequences, the actual positions of modified amino acids in the sequence generally differ. In this entry the following conventions are used: H3T3ph = phosphorylated Thr-4; H3K4me1/2/3 = mono-, di- and trimethylated Lys-5; H3K9ac = acetylated Lys-10; H3K9me1/2/3 = mono-, di- and trimethylated Lys-10; H3S10ph = phosphorylated Ser-11; H3T11ph = phosphorylated Thr-12; H3K14ac = acetylated Lys-15; H3K18ac = acetylated Lys-19; H3K18me = methylated Lys-19; H3K23ac = acetylated Lys-24; H3K23me = methylated Lys-24; H3K27me = methylated Lys-28; H3S28ph = phosphorylated Ser-29; H3K36me = methylated Lys-37.