Histone H2AX Phosphorylation Independent of ATM after X-irradiation in Mouse Liver and Kidney in situ

Histone H2AX undergoes phosphorylation at Ser-139 (gamma-H2AX) rapidly in response to DNA double-strand breaks (DSBs) induced by ionizing radiation. The post-translational modification of H2AX plays a central role in responses to radiation, including the repair of DSBs. Although ataxia telangiectasia mutated (ATM) kinase phosphorylates Ser-139 of H2AX in vitro, the post-translational modification pattern and the modifier of H2AX in organs in vivo are not yet well understood. In this study, we detected phosphorylation of H2AX at Ser-139 in cells of the mouse ear, liver, and kidney after X-irradiation. Moreover, the phosphorylation of H2AX was regulated depending on not only the cell type, but also the organ type and the localization of a cell type in an organ. Following X-irradiation, H2AX was phosphorylated in the liver and kidney of ATM gene knockout mice, suggesting that ATM kinase is not essential for phosphorylation of H2AX in these organs after X-irradiation in vivo

Dynamic change of histone H2AX phosphorylation independent of ATM and DNA-PK in mouse skin in situ.

Histone H2AX undergoes phosphorylation on Ser 139 (gamma-H2AX) rapidly in response to DNA double-strand breaks induced by exogenous stimuli, such as ionizing radiation. However, the endogenous phosphorylation pattern and modifier of H2AX remain unclear. Here we show that H2AX is regulated physically at the level of phosphorylation at Ser139 during a hair cycle in the mouse skin. In anagen hair follicles, gamma-H2AX-positive cells were observed in the outer root sheath (ORS) and hair bulb in a cycling inferior region but not in a permanent superficial region. In telogen hair follicles, gamma-H2AX-positive cells were only detected around the germ cell cap. In contrast, following X-irradiation, gamma-H2AX was observed in various cell types including the ORS cells in the permanent superficial region. Furthermore, gamma-H2AX-positive cells were detected in the skin of mice lacking either ATM or DNA-PK, suggesting that these kinases are not essential for phosphorylation in vivo