Li F, Phadte A S, Bhatia M, Barndt S, Monte Carlo Iii A R, Hou C-F D, Yang R, Strock S, Pluciennik A
Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, PA, USA.
Department of Biochemistry and Biophysics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA.
Nat Commun. 2025 May 14;16(1):4411. doi: 10.1038/s41467-025-59323-y.
FAN1 is a DNA dependent nuclease whose proper function is essential for maintaining human health. For example, a genetic variant in FAN1, Arg507 to His hastens onset of Huntington's disease, a repeat expansion disorder for which there is no cure. How the Arg507His mutation affects FAN1 structure and enzymatic function is unknown. Using cryo-EM and biochemistry, we have discovered that FAN1 arginine 507 is critical for its interaction with PCNA, and mutation of Arg507 to His attenuates assembly of the FAN1-PCNA complex on a disease-relevant extrahelical DNA extrusions formed within DNA repeats. This mutation concomitantly abolishes PCNA-FAN1-dependent cleavage of such extrusions, thus unraveling the molecular basis for a specific mutation in FAN1 that dramatically hastens the onset of Huntington's disease. These results underscore the importance of PCNA to the genome stabilizing function of FAN1.
FAN1是一种依赖DNA的核酸酶，其正常功能对于维持人类健康至关重要。例如，FAN1中的一种基因变异，即从精氨酸507突变为组氨酸，会加速亨廷顿舞蹈病的发病，这是一种无法治愈的重复序列扩张性疾病。精氨酸507突变为组氨酸的突变如何影响FAN1的结构和酶功能尚不清楚。利用冷冻电镜和生物化学方法，我们发现FAN1的精氨酸507对其与增殖细胞核抗原（PCNA）的相互作用至关重要，并且将精氨酸507突变为组氨酸会减弱FAN1-PCNA复合物在DNA重复序列内形成的与疾病相关的螺旋外DNA突出结构上的组装。这种突变同时消除了PCNA-FAN1依赖的此类突出结构的切割，从而揭示了FAN1中一种特定突变显著加速亨廷顿舞蹈病发病的分子基础。这些结果强调了PCNA对FAN1基因组稳定功能的重要性。
