Beijing Key Laboratory of Bioprocess, College of Life Science and Technology, Beijing University of Chemical Technology, Beijing 100029, China.
Department of Chemistry, Binghamton University, State University of New York, Vestal, NY 13902, USA.
J Mol Biol. 2020 Jan 17;432(2):467-483. doi: 10.1016/j.jmb.2019.11.017. Epub 2019 Dec 2.
The RNA-binding protein fused in sarcoma (FUS) forms physiological granules and pathological fibrils, which facilitate RNA functions and cause neurodegenerative diseases, respectively. Phosphorylation at Ser/Thr residues may regulate the functional assembly of FUS and prevent pathological aggregation in cells. However, the low-complexity nature of the FUS sequence makes it challenging to characterize how phosphorylation of specific sites within the core amyloid-forming segment affects aggregation. Taking advantage of the recently solved molecular structures of the fibrillar core of the FUS low-complexity (FUS-LC) domain, we systematically investigated the aggregation of repeated segments within the core. We identified a segment with a strong amyloid-forming tendency that induced the aggregation of FUS-LC domain in phase-separated liquid droplets and further seeded the aggregation of full-length FUS. The aggregation propensity and seeding ability of this amyloid-forming segment were modulated by site-specific phosphorylation. Solid-state nuclear magnetic resonance (NMR) spectroscopy and computational modeling implied that site-specific phosphorylation at Ser61 plays key roles in FUS assembly by disrupting both intra- and intermolecular interactions that maintain the amyloid core structure.
融合于肉瘤的 RNA 结合蛋白（FUS）形成生理颗粒和病理纤维，分别促进 RNA 功能和引起神经退行性疾病。丝氨酸/苏氨酸残基的磷酸化可能调节 FUS 的功能组装并防止细胞中的病理性聚集。然而，FUS 序列的低复杂度性质使得难以描述核心淀粉样形成片段内特定位点的磷酸化如何影响聚集。利用最近解决的 FUS 低复杂度（FUS-LC）域纤维状核心的分子结构，我们系统地研究了核心内重复片段的聚集。我们鉴定出一个具有强烈淀粉样形成倾向的片段，该片段在相分离的液滴中诱导 FUS-LC 域的聚集，并进一步引发全长 FUS 的聚集。该淀粉样形成片段的聚集倾向和种子形成能力受到特定位点磷酸化的调节。固态核磁共振（NMR）光谱和计算建模表明，丝氨酸 61 位的特异性磷酸化通过破坏维持淀粉样核心结构的分子内和分子间相互作用，在 FUS 组装中发挥关键作用。
