Nguyen Trang Thu, Mazzucco Giulia, Kyriacou Eftychia, Lunardi Thomas, Brandl Leona, Ahmed Wareed, Doksani Ylli, Lingner Joachim
Swiss Institute for Experimental Cancer Research (ISREC), School of Life Sciences, École Polytechnique Fédérale de Lausanne (EPFL), 1015 Lausanne, Switzerland.
IFOM ETS - The AIRC Institute of Molecular Oncology, 20139 Milan, Italy.
Nucleic Acids Res. 2025 Apr 10;53(7). doi: 10.1093/nar/gkaf285.
Telomeres are the nucleoprotein structures at chromosome ends. Telomeres are particularly sensitive to oxidative stress, which can induce telomere damage, shortening, and premature cellular senescence. How oxidative damage influences telomere structure has not been defined. Here, we induce oxidative damage at telomeres using menadione, which damages mitochondria mimicking intrinsic oxidative stress. We find that oxidative stress induces at telomeres single-stranded DNA breaks, internal DNA loop structures, dissociation of the shelterin component TRF1, upregulation of TERRA long noncoding RNA, and increased DNA:RNA hybrid structures known as R-loops. R-loop formation is enhanced not only in cis at telomeres, which show increased TERRA transcription, but also in trans at telomeres at which TERRA transcription is not induced indicating post-transcriptional R-loop formation. Finally, we show that oxidative damage induced R-loop formation requires TRF2, whose R-loop promoting activity may be unleashed upon TRF1 dissociation from telomeres. Altogether, our findings uncover in response to oxidative stress major remodelling of telomeric DNA, RNA, and shelterin complexes, and they unravel a physiological role of TRF2's ability to stimulate TERRA R-loop formation. We propose that the identified structural changes may facilitate DNA damage signalling and repair pathways to maintain telomere integrity during development and aging.
端粒是染色体末端的核蛋白结构。端粒对氧化应激特别敏感，氧化应激可诱导端粒损伤、缩短和细胞过早衰老。氧化损伤如何影响端粒结构尚未明确。在此，我们使用甲萘醌在端粒处诱导氧化损伤，甲萘醌可损伤线粒体，模拟内源性氧化应激。我们发现氧化应激在端粒处诱导单链DNA断裂、内部DNA环结构、端粒保护蛋白组分TRF1解离、TERRA长链非编码RNA上调以及DNA:RNA杂交结构（即R环）增加。R环形成不仅在端粒顺式作用中增强，端粒处TERRA转录增加，而且在端粒反式作用中也增强，端粒处TERRA转录未被诱导，表明存在转录后R环形成。最后，我们表明氧化损伤诱导的R环形成需要TRF2，其促进R环形成的活性可能在TRF1从端粒解离后被释放。总之，我们的研究结果揭示了氧化应激反应中端粒DNA、RNA和端粒保护蛋白复合物的主要重塑过程，并揭示了TRF2刺激TERRA R环形成能力的生理作用。我们提出，所确定的结构变化可能促进DNA损伤信号传导和修复途径，以在发育和衰老过程中维持端粒完整性。
