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 and Ser-29 during M phase. Phosphorylation of Ser-11 requires air-2 but not air-1. Dephosphorylated by gsp-1 and/or gsp-2 during chromosome segregation. Acetylation is generally linked to gene activation. Methylation at Lys-5 is linked to gene activation and is absent from male inactive X chromosome chromatin. Methylation at Lys-10 is linked to gene repression and is enriched in male inactive X chromosome chromatin. Methylation at Lys-37 occurs on the entire length of autosomes during meiotic prophase. Trimethylation at Lys-10 and Lys-37 is specifically antagonized by jmjd-2. Dimethylation and trimethylation at Lys-28 occurs in all nuclei. The mes-2-mes-3-mes-6 complex may be responsible for Lys-28 methylation in most of the germline and in the early embryo. Belongs to the histone H3 family.