gammaH2AX as a checkpoint maintenance signal.

A key function of the conserved signaling cascade triggered by DNA damage is to promote the arrest or pause of cell cycle progression, a phenomenon commonly termed a "checkpoint". This response allows time for DNA repair to proceed before entering a new phase of the cell cycle. Although much is known about the initiation and propagation of this signaling pathway, much less is understood about the mechanisms that lead to its extinction. Recent work highlights a role for H2AX phosphorylation as a checkpoint maintenance factor and of its dephosphorylation as a signal for resumption of the cell cycle.