Bouley Julien, Saad Lina, Grall Romain, Schellenbauer Amelie, Biard Denis, Paget Vincent, Morel-Altmeyer Sandrine, Guipaud Olivier, Chambon Christophe, Salles Bernard, Maloum Karim, Merle-Béral Hélène, Chevillard Sylvie, Delic Jozo
Laboratoire de Cancérologie Expérimentale, Institut de Radiobiologie Cellulaire et Moléculaire (IRCM), Commissariat à l'Energie Atomique et aux Energies Renouvelables (CEA), 92265 Fontenay aux Roses, France.
Laboratoire de Spectrométrie de Masse, Stallergens, 92160 Antony, France.
Oncotarget. 2015 Sep 29;6(29):27980-8000. doi: 10.18632/oncotarget.4735.
Ku70-dependent canonical nonhomologous end-joining (c-NHEJ) DNA repair system is fundamental to the genome maintenance and B-cell lineage. c-NHEJ is upregulated and error-prone in incurable forms of chronic lymphocytic leukemia which also displays telomere dysfunction, multiple chromosomal aberrations and the resistance to DNA damage-induced apoptosis. We identify in these cells a novel DNA damage inducible form of phospho-Ku70. In vitro in different cancer cell lines, Ku70 phosphorylation occurs in a heterodimer Ku70/Ku80 complex within minutes of genotoxic stress, necessitating its interaction with DNA damage-induced kinase pS2056-DNA-PKcs and/or pS1981-ATM. The mutagenic effects of phospho-Ku70 are documented by a defective S/G2 checkpoint, accelerated disappearance of γ-H2AX foci and kinetics of DNA repair resulting in an increased level of genotoxic stress-induced chromosomal aberrations. Together, these data unveil an involvement of phospho-Ku70 in fast but inaccurate DNA repair; a new paradigm linked to both the deregulation of c-NHEJ and the resistance of malignant cells.
依赖Ku70的经典非同源末端连接（c-NHEJ）DNA修复系统对于基因组维持和B细胞谱系至关重要。c-NHEJ在无法治愈的慢性淋巴细胞白血病中上调且易出错，这种疾病还表现出端粒功能障碍、多种染色体畸变以及对DNA损伤诱导的凋亡的抗性。我们在这些细胞中鉴定出一种新型的磷酸化Ku70的DNA损伤诱导形式。在体外不同癌细胞系中，在基因毒性应激几分钟内，Ku70磷酸化发生在异源二聚体Ku70/Ku80复合物中，这需要其与DNA损伤诱导激酶pS2056-DNA-PKcs和/或pS1981-ATM相互作用。磷酸化Ku70的诱变作用通过缺陷的S/G2检查点、γ-H2AX焦点的加速消失以及DNA修复动力学得以证明，这些导致基因毒性应激诱导的染色体畸变水平增加。总之，这些数据揭示了磷酸化Ku70参与快速但不准确的DNA修复；这是一种与c-NHEJ失调和恶性细胞抗性相关的新范式。
