γH2AX and its role in DNA double-strand break repair

One of the earliest responses to a DNA double-strand break (DSB) is the carboxy-terminal phosphorylation of budding yeast H2A (metazoan histone H2AX) to create gamma H2A (or gamma Eta 2 alpha X). This chromatin modification stretches more than tens of kilobases around the DSB and has been proposed to play numerous roles in break recognition and repair, although it may not be the primary signal for many of these events. Studies suggest that gamma H2A(X) has 2 more direct roles: (i) to recruit cohesin around the DSB, and (ii) to maintain a checkpoint arrest. Recent work has identified other factors, including chromatin remodelers and protein phosphatases, which target gamma H2A(X) and regulate DSB repair/recovery.