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. This variant is enriched at promoters, it may keep them in a repressed state until the appropriate activation signal is received. Near telomeres, it may counteract gene silencing caused by the spread of heterochromatin proteins. Required for the RNA polymerase II and SPT15/TBP recruitment to the target genes. Involved in chromosome stability (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. H2A or its variant H2A.Z forms a heterodimer with H2B. H2A.Z associates with the VPS72/SWC2 subunit of the SWR1 chromatin remodeling complex. Interacts also with RBP1/DNA-directed RNA polymerase II largest subunit (By similarity). Acetylated once deposited into chromatin. Belongs to the histone H2A family.