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. 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. Acetylated to form H3K9ac (11%), H3K14ac (17%), H3K18ac (11%), H3K23ac (16%) and H3K27ac (7%). H3K4, H3K35 and H3K36 are not acetylated. H3K4me prevents acetylation. 32% of the histone H3 are acetylated with, on average, 2.4 acetyl-Lys. They are all continuously deacatylated and re-acetylated with a half-life of approximately 2 min. Monomethylated to form H3K4me1 (81%), H3K9me1 (16%), H3K27me1 (25%), H3K35me1 (25%) and H3K36me1 (5%). No methylation at H3K14, H3K18 and H3K23. Methylated by a protein complex that includes Mut11. Set1 methylates specifically H3K4. H3K4me1 is associated with silenced euchromatin. Set3 forms H3K9me1, while H3K9me2 is undetected. H3K9me1 is specifically associated with silent, multi-copy transgenes. No phosphorylation detected. 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: H3K4 = Lys-5; H3K4me = methylated Lys-5; H3K9ac = acetylated Lys-10; H3K9me = methylated Lys-10; H3S10ph = phosphorylated Ser-11; H3T11ph = phosphorylated Thr-12; H3K14 = Lys-15; H3K14ac = acetylated Lys-15; H3K18 = Lys-19; H3K18ac = acetylated Lys-19; H3K23 = Lys-24; H3K23ac = acetylated Lys-24; H3K27ac = acetylated Lys-28; H3K27me = methylated Lys-28; H3K35 = Lys-36; H3K35me = methylated Lys-36; H3K36 = Lys-37; H3K36me = methylated Lys-37.