Yano Ken-ichi, Morotomi-Yano Keiko, Wang Shih-Ya, Uematsu Naoya, Lee Kyung-Jong, Asaithamby Aroumougame, Weterings Eric, Chen David J
Division of Molecular Radiation Biology, Department of Radiation Oncology, University of Texas Southwestern Medical Center at Dallas, 5801 Forest Park Road, Dallas, TX 75390-9187, USA.
EMBO Rep. 2008 Jan;9(1):91-6. doi: 10.1038/sj.embor.7401137. Epub 2007 Dec 7.
XRCC4-like factor (XLF)--also known as Cernunnos--has recently been shown to be involved in non-homologous end-joining (NHEJ), which is the main pathway for the repair of DNA double-strand breaks (DSBs) in mammalian cells. XLF is likely to enhance NHEJ by stimulating XRCC4-ligase IV-mediated joining of DSBs. Here, we report mechanistic details of XLF recruitment to DSBs. Live cell imaging combined with laser micro-irradiation showed that XLF is an early responder to DSBs and that Ku is essential for XLF recruitment to DSBs. Biochemical analysis showed that Ku-XLF interaction occurs on DNA and that Ku stimulates XLF binding to DNA. Unexpectedly, XRCC4 is dispensable for XLF recruitment to DSBs, although photobleaching analysis showed that XRCC4 stabilizes the binding of XLF to DSBs. Our observations showed the direct involvement of XLF in the dynamic assembly of the NHEJ machinery and provide mechanistic insights into DSB recognition.
XRCC4样因子（XLF）——也被称为Cernunnos——最近已被证明参与非同源末端连接（NHEJ），这是哺乳动物细胞中DNA双链断裂（DSB）修复的主要途径。XLF可能通过刺激XRCC4-连接酶IV介导的DSB连接来增强NHEJ。在此，我们报告了XLF募集到DSB的机制细节。活细胞成像结合激光微照射表明，XLF是DSB的早期应答者，并且Ku对于XLF募集到DSB至关重要。生化分析表明，Ku与XLF的相互作用发生在DNA上，并且Ku刺激XLF与DNA结合。出乎意料的是，尽管光漂白分析表明XRCC4可稳定XLF与DSB的结合，但XRCC4对于XLF募集到DSB是可有可无的。我们的观察结果表明XLF直接参与了NHEJ机制的动态组装，并为DSB识别提供了机制上的见解。
