The phosphorylation of histone H3 plays an important role in gene expression, chromatin remodeling, chromosome condensation, and cell division. Histone H3 phosphorylation may initiate at different phases of the cell division in different organisms, but metaphase chromosomes are always found to be heavily phosphorylated. H3 phosphorylation at serine 28 is coupled with mitotic chromosome condensation in diverse mammalian cell lines.