Department of Biochemistry and Molecular Biology, SUNY Upstate Medical University, 750 East Adams Street, Syracuse, NY 13210, USA.
Bioinformatics Institute, Agency for Science Technology and Research (A(∗)STAR), 30 Biopolis Street, #07-01 Matrix, Singapore 138671, Singapore.
Cell Rep. 2020 Sep 22;32(12):108179. doi: 10.1016/j.celrep.2020.108179.
Fragile X syndrome (FXS) is a neurodevelopmental disorder caused by mutations in the FMR1 gene and deficiency of a functional FMRP protein. FMRP is known as a translation repressor whose nuclear function is not understood. We investigated the global impact on genome stability due to FMRP loss. Using Break-seq, we map spontaneous and replication stress-induced DNA double-strand breaks (DSBs) in an FXS patient-derived cell line. We report that the genomes of FXS cells are inherently unstable and accumulate twice as many DSBs as those from an unaffected control. We demonstrate that replication stress-induced DSBs in FXS cells colocalize with R-loop forming sequences. Exogenously expressed FMRP in FXS fibroblasts ameliorates DSB formation. FMRP, not the I304N mutant, abates R-loop-induced DSBs during programmed replication-transcription conflict. These results suggest that FMRP is a genome maintenance protein that prevents R-loop accumulation. Our study provides insights into the etiological basis for FXS.
脆性 X 综合征（FXS）是一种由 FMR1 基因突变和功能性 FMRP 蛋白缺失引起的神经发育障碍。FMRP 被称为翻译抑制剂，其核功能尚不清楚。我们研究了由于 FMRP 缺失对基因组稳定性的整体影响。我们使用 Break-seq 技术，在 FXS 患者来源的细胞系中绘制自发和复制应激诱导的 DNA 双链断裂（DSBs）。我们报告说，FXS 细胞的基因组天生不稳定，积累的 DSB 是未受影响对照细胞的两倍。我们证明，FXS 细胞中复制应激诱导的 DSB 与 R 环形成序列共定位。在 FXS 成纤维细胞中过表达 FMRP 可改善 DSB 的形成。FMRP（而非 I304N 突变体）可减轻程序性复制-转录冲突期间 R 环诱导的 DSB。这些结果表明 FMRP 是一种基因组维护蛋白，可防止 R 环积累。我们的研究为 FXS 的病因学基础提供了新的见解。
