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 (By similarity). 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 (By similarity). Phosphorylated by IPL1 to form H3S10ph. H3S10ph promotes subsequent H3K14ac formation by GCN5 and is required for transcriptional activation through TBP recruitment to the promoters (By similarity). Mono-, di- and trimethylated by the COMPASS complex to form H3K4me1/2/3. H3K4me activates gene expression by regulating transcription elongation and plays a role in telomere length maintenance. H3K4me enrichment correlates with transcription levels, and occurs in a 5' to 3' gradient with H3K4me3 enrichment at the 5'-end of genes, shifting to H3K4me2 and then H3K4me1. Methylated by SET2 to form H3K36me. H3K36me represses gene expression. Methylated by DOT1 to form H3K79me. H3K79me is required for association of SIR proteins with telomeric regions and for telomeric silencing. The COMPASS-mediated formation of H3K4me2/3 and the DOT1-mediated formation of H3K79me require H2BK123ub1 (By similarity). Acetylation of histone H3 leads to transcriptional activation. H3K14ac formation by GCN5 is promoted by H3S10ph. H3K14ac can also be formed by ESA1. H3K56ac formation occurs predominantly in newly synthesized H3 molecules during G1, S and G2/M of the cell cycle and may be involved in DNA repair (By similarity). 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: H3K4me1/2/3 = mono-, di- and trimethylated Lys-5; H3K9ac = acetylated Lys-10; H3K9me1 = monomethylated Lys-10; H3S10ph = phosphorylated Ser-11; H3K14ac = acetylated Lys-15; H3K14me2 = dimethylated Lys-15; H3K18ac = acetylated Lys-19; H3K18me1 = monomethylated Lys-19; H3K23ac = acetylated Lys-24; H3K23me1 = monomethylated Lys-24; H3K27ac = acetylated Lys-28; H3K27me1/2/3 = mono-, di- and trimethylated Lys-28; H3K36ac = acetylated Lys-37; H3K36me1/2/3 = mono-, di- and trimethylated Lys-37; H3K56ac = acetylated Lys-57; H3K64ac = acetylated Lys-65; H3K79me1/2/3 = mono-, di- and trimethylated Lys-80.