Department of Biochemistry and Molecular Biology, Southern Research Institute, Birmingham, United States.
Radiother Oncol. 2013 Sep;108(3):403-8. doi: 10.1016/j.radonc.2013.06.017. Epub 2013 Jul 25.
Activation of the DNA damage responsive protein kinase ATM is a critical step for cellular survival in response to ionizing irradiation (IR). Direct targets of ATM regulating radiosensitivity remain to be fully investigated. We have recently reported that ATM phosphorylates the transcriptional repressor Snail on Serine 100. We aimed to further study the functional significance of ATM-mediated Snail phosphorylation in response to IR.
We transfected vector-only, wild-type, the Serine 100 to alanine (S100A) or to glutamic acid (S100E) substitution of Snail into various cell lines. We assessed colony formation, γ-H2AX focus formation and the invasion index in the cells treated with or without IR.
We found that over-expression of the S100A mutant Snail in HeLa cells significantly increased radiosensitivity. Meanwhile the expression of S100E, a phospho-mimicking mutation, resulted in enhanced radio-resistance. Interestingly, S100E could rescue the radiosensitive phenotype in ATM-deficient cells. We also found that expression of S100E increased γ-H2AX focus formation and compromised inhibition of invasion in response to IR independent of cell survival.
ATM-mediated Snail Serine 100 phosphorylation in response to IR plays an important part in the regulation of radiosensitivity.
DNA 损伤反应蛋白激酶 ATM 的激活是细胞在电离辐射（IR）下存活的关键步骤。ATM 调节放射敏感性的直接靶标仍有待充分研究。我们最近报道 ATM 磷酸化转录抑制因子 Snail 的丝氨酸 100。我们旨在进一步研究 ATM 介导的 Snail 磷酸化对 IR 的反应的功能意义。
我们将空载载体、野生型、丝氨酸 100 突变为丙氨酸（S100A）或谷氨酸（S100E）的 Snail 转染到各种细胞系中。我们评估了细胞在接受或不接受 IR 处理后的集落形成、γ-H2AX 焦点形成和侵袭指数。
我们发现，在 HeLa 细胞中过表达 S100A 突变型 Snail 显着增加了放射敏感性。同时，磷酸化模拟突变 S100E 的表达导致放射抗性增强。有趣的是，S100E 可以挽救 ATM 缺陷细胞的放射敏感表型。我们还发现，S100E 的表达增加了 γ-H2AX 焦点的形成，并在不影响细胞存活的情况下削弱了对 IR 的侵袭抑制。
ATM 介导的 Snail 丝氨酸 100 在 IR 下的磷酸化在调节放射敏感性方面起着重要作用。
