Adamowicz Marek, d'Adda di Fagagna Fabrizio, Vermezovic Jelena
IFOM Foundation - FIRC Institute of Molecular Oncology Foundation, 20139 Milan, Italy; Genome Damage and Stability Centre, School of Life Sciences, University of Sussex, Falmer, Brighton BN1 9RH, UK.
IFOM Foundation - FIRC Institute of Molecular Oncology Foundation, 20139 Milan, Italy; Istituto di Genetica Molecolare, Consiglio Nazionale delle Ricerche, 27100 Pavia, Italy.
Mutat Res. 2018 Mar;808:20-27. doi: 10.1016/j.mrfmmm.2018.01.003.
DNA-dependent protein kinase catalytic subunit (DNA-PKcs) controls one of the most frequently used DNA repair pathways in a cell, the non-homologous end joining (NHEJ) pathway. However, the exact role of DNA-PKcs in NHEJ remains poorly defined. Here we show that NOTCH1 attenuates DNA-PKcs-mediated autophosphorylation, as well as the phosphorylation of its specific substrate XRCC4. Surprisingly, NOTCH1-expressing cells do not display any significant impairment in the DNA damage repair, nor cellular survival, and remain sensitive to small molecule DNA-PKcs inhibitor. Additionally, in vitro DNA-PKcs kinase assay shows that NOTCH1 does not inhibit DNA-PKcs kinase activity, implying that NOTCH1 acts on DNA-PKcs through a different mechanism. Together, our set of results suggests that NOTCH1 is a physiological modulator of DNA-PKcs, and that it can be a useful tool to clarify the mechanisms by which DNA-PKcs governs NHEJ DNA repair.
DNA依赖性蛋白激酶催化亚基（DNA-PKcs）控制细胞中最常用的DNA修复途径之一，即非同源末端连接（NHEJ）途径。然而，DNA-PKcs在NHEJ中的具体作用仍不清楚。在此我们表明，NOTCH1可减弱DNA-PKcs介导的自身磷酸化及其特异性底物XRCC4的磷酸化。令人惊讶的是，表达NOTCH1的细胞在DNA损伤修复或细胞存活方面未表现出任何显著损伤，并且对小分子DNA-PKcs抑制剂仍敏感。此外，体外DNA-PKcs激酶分析表明NOTCH1并不抑制DNA-PKcs激酶活性，这意味着NOTCH1通过不同机制作用于DNA-PKcs。总之，我们的一系列结果表明NOTCH1是DNA-PKcs的生理调节剂，并且它可能是阐明DNA-PKcs调控NHEJ DNA修复机制的有用工具。
