H3 is a core component of the nucleosome that serves to wrap and compact DNA into chromatin.Histones therefore, limit the accessibility of DNA, providing mechanisms for transcription regulation, DNA repair and replication and chromosomal stability.During mitosis, H3 is phosphorylated at serine 28.This phosphorylation coincides with chromosome condensation initiated at prophase and disappears at late anaphase H3 has been demonstrated to be phosphorylated by the action of MLTK-alpha (mixed linage kinase-like mitogen activated protein triple kinase alpha) in response to ultraviolet B light and epidermal growth factor, as well as Aurora-B during mitosis.