Variant histone H2A which can replace H2A in some nucleosomes. 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. Important for chromosomal structure and function, possibly including a role in controlling the fidelity of chromosomal segregation during mitosis. Plays an important role in maintaining a silenced chromatin state at centromeres and in the architecture of anaphase chromosomes. 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. H2A or its variant H2A.Z forms a heterodimer with H2B. Component of the SWR1 and INO80 chromatin-remodeling complexes. Acetylated at the N-terminus. N-terminal acetylation is essential for function. Belongs to the histone H2A family. Extended N-terminus. Extended N-terminus.