Specific ATM-mediated phosphorylation dependent on radiation quality.

To determine whether the physical differences between high- and low-LET radiation are reflected in the biological responses of exposed cells, we detailed phospho-protein profiles of three proteins functional in radiation repair and signal transduction. Detailing gamma-H2AX, pATF2 Ser490/498 and pSMC1 Ser957 kinetics after X-ray and iron-ion exposure also provides a window into understanding the underlying cellular responses. Phosphorylated forms of these proteins have been documented to co-localize at sites of double-strand breaks (DSBs) after low-LET radiation exposures, and two of these phosphorylations, pATF2 and pSMC1, are specifically dependent on ATM.