Presentation Histone H2AX phosphorylation after hydrogen peroxide treatment is mediated by ATR and not depending on DNA double-strand breaks

Katsube, Takanori  ,  Mori, Masahiko  ,  Tsuji, Hideo  ,  Shiomi, Tadahiro  ,  Bing, Wang  ,  Qiang,, LIU  ,  Nenoi, Mitsuru  ,  Onoda, Makoto

H2AX is a variant form of the nucleosomal protein, histone H2A. H2AX is phosphorylated on its S139 site by ATM in response to DNA double strand breaks (DSBs). The nuclear foci of phosphorylated histone H2AX (γH2AX) are frequently used as a marker for DSBs following ionizing radiation (IR). However, recent studies reported that γH2AX foci do not necessarily correlate with DSBs under other conditions. When cells are exposed to replication stress, H2AX is phosphorylated by ATR in response to single-stranded DNA arisen from stalled replication forks in S-phase cells. We showed that γH2AX foci induced by oxidative stress in hydrogen peroxide (H2O2)-treated cells displayed several different features from those induced by IR. The magnitude of γH2AX induction was heterogeneous among H2O2-treated cells. Some cells expressed small discrete γH2AX foci, whereas others expressed a gross γH2AX signal that was distributed throughout the nucleus. Oxidative stress-induced γH2AX was eliminated in DSB repair-deficient mutant cells as efficiently as in wild-type cells and was not necessarily accompanied by phosphorylated ATM or 53BP1 foci. Analyses using specific inhibitors showed that ATR, rather than ATM, was the prominent kinase mediating the oxidative stress response. These results suggest that a major fraction of γH2AX induced by oxidative stress is not associated with DSBs. Single-stranded DNA arisen from stalled replication forks can cause the ATR-mediated induction of γH2AX. However, oxidative stress appeared to induce γH2AX in both S- and non-S-phase cells. These results suggest that there may be another pathway leading to the ATR-mediated induction of γH2AX in non-S-phase cells without DSBs.

Number of accesses :  

Other information