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. Phosphorylated at Ser-11. This is required for transcriptional activation through TBP recruitment to the promoters. Phosphorylation at Ser-11 also promotes subsequent acetylation at Lys-15 (By similarity). Mono-, di- and trimethylation of Lys-5 by the COMPASS complex activates gene expression by regulating transcription elongation and plays a role in telomere length maintenance. Lys-5 methylation enrichment correlates with transcription levels, and occurs in a 5' to 3' gradient with tri-methyl enrichment at the 5'-end of genes, shifting to di-methyl and then mono-methyl. The COMPASS mediated di and trimethylation of Lys-5 requires histone H2B monoubiquitination. Methylation of Lys-37 by SET2 represses gene expression. Methylation of Lys-80 by DOT1 is required for association of SIR proteins with telomeric regions and for telomeric silencing (By similarity). Acetylation of histone H3 leads to transcriptional activation. Acetylation at Lys-15 is promoted by the phosphorylation at Ser-11. Acetylation at Lys-57 occurs predominantly in newly synthesized H3 molecule 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.