HIST3H2A is a member of histones, which are a complex family of highly conserved basic proteins responsible for packaging chromosomal DNA into nucleosomes. Covalent modification of histones is important in regulating chromatin dynamics and transcription. One example of such modification is ubiquitination, which mainly occurs on histones H2A and H2B. E3 ubiquitin ligase complex is specific for histone H2A (HIST3H2A). Reducing the expression of Ring2 results in a dramatic decrease in the level of ubiquitinated H2A in HeLa cells. DNA damage induces monoubiquitylation of histone H2A (HIST3H2A) in the vicinity of DNA lesions.