Porro Antonio, Mohiuddin Mohiuddin, Zurfluh Christina, Spegg Vincent, Dai Jingqi, Iehl Florence, Ropars Virginie, Collotta Giulio, Fishwick Keri M, Mozaffari Nour L, Guérois Raphaël, Jiricny Josef, Altmeyer Matthias, Charbonnier Jean-Baptiste, Pearson Christopher E, Sartori Alessandro A
Institute of Molecular Cancer Research, University of Zurich, Zurich, Switzerland.
Program of Genetics and Genome Biology, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada.
Sci Adv. 2021 Jul 30;7(31). doi: 10.1126/sciadv.abf7906. Print 2021 Jul.
FAN1, a DNA structure-specific nuclease, interacts with MLH1, but the repair pathways in which this complex acts are unknown. FAN1 processes DNA interstrand crosslinks (ICLs) and FAN1 variants are modifiers of the neurodegenerative Huntington's disease (HD), presumably by regulating HD-causing CAG repeat expansions. Here, we identify specific amino acid residues in two adjacent FAN1 motifs that are critical for MLH1 binding. Disruption of the FAN1-MLH1 interaction confers cellular hypersensitivity to ICL damage and defective repair of CAG/CTG slip-outs, intermediates of repeat expansion mutations. FAN1-S126 phosphorylation, which hinders FAN1-MLH1 association, is cell cycle-regulated by cyclin-dependent kinase activity and attenuated upon ICL induction. Our data highlight the FAN1-MLH1 complex as a phosphorylation-regulated determinant of ICL response and repeat stability, opening novel paths to modify cancer and neurodegeneration.
FAN1是一种DNA结构特异性核酸酶，它与MLH1相互作用，但该复合物发挥作用的修复途径尚不清楚。FAN1处理DNA链间交联（ICL），并且FAN1变体是神经退行性疾病亨廷顿舞蹈症（HD）的修饰因子，大概是通过调节导致HD的CAG重复序列扩增来实现的。在这里，我们确定了FAN1两个相邻基序中的特定氨基酸残基，它们对MLH1结合至关重要。FAN1与MLH1相互作用的破坏会使细胞对ICL损伤高度敏感，并且对CAG/CTG滑脱（重复扩增突变的中间体）的修复存在缺陷。阻碍FAN1与MLH1结合的FAN1-S126磷酸化受细胞周期蛋白依赖性激酶活性的细胞周期调控，并在ICL诱导时减弱。我们的数据突出了FAN1-MLH1复合物作为ICL反应和重复序列稳定性的磷酸化调节决定因素，为修饰癌症和神经退行性疾病开辟了新途径。
