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. Has antimicrobial activity against the Gram-positive bacterium M.luteus. 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. Monoubiquitination of Lys-119 gives a specific tag for epigenetic transcriptional repression. Phosphorylation of Ser-2 directly represses transcription. May be phosphorylated. Acetylation on Ser-2. Acetylation and phosphorylation on Ser-2. Belongs to the histone H2A family.