HISTONE H3 PHOSPHORYLATION IN RESPONSE TO DNA‐DAMAGE

Abstract

Exposure to physical and chemical agents such as ionizing radiation, reactive oxygen species, alkylating agents, telomerase and topoisomerase inhibitors, causes DNA damage. Although mechanisms of DNA repair are well established, the relationship between chromatin remodeling and the DNA damage response remains unclear. Histones are downstream targets of many signaling cascades. The sequence and pattern of histone modifications likely dictates specific functional outcomes. Loss of histone H3 S10 phosphorylation disrupts chromosome condensation causing abnormal segregation, and H3 S28 phosphorylation also contributes to chromosome condensation. We therefore investigated changes in histone H3 phosphorylation on S10, S28 and S31 in response to different DNA-damaging agents. Interestingly, histone H3.3 S31 phosphorylation only increased when cells were treated with microtubule-disrupting agents (colcemid and paclitaxel) which arrest cells at metaphase and cause mitotic catastrophe. Moreover, although the tumor promoter 12-O-teteradecanoylphorbol-13-acetate (TPA) and epidermal growth factor (EGF) stimulated histone H3 S10 and S28 phosphorylation, as did colcemid and paclitaxel, TPA and EGF did not induce S31 phosphorylation. Thus, patterns of histone H3 phosphorylation vary dependent upon the stimulus, and histone H3.3 S31 phosphorylation appears to be restricted to metaphase, since immunofluorescence experiments confirmed that histone H3.3 S31 phosphorylation is present in late prometaphase, and dramatically diminishes at early anaphase. H3.3 S31 phosphorylation may serve as a marker for cells undergoing cell death via mitotic catastrophe (RO1 DK59491, P30 ES 06694)