Telomere shortening rates must be regulated to prevent premature replicative senescence. TERRA R-loops become stabilized at critically short telomeres to promote their elongation through homology-directed repair (HDR), thereby counteracting senescence onset. Using a non-bias proteomic approach to detect telomere binding factors, we identified Npl3, an RNA-binding protein previously implicated in multiple RNA biogenesis processes. Using chromatin immunoprecipitation and RNA immunoprecipitation, we demonstrate that Npl3 interacts with TERRA and telomeres. Furthermore, we show that Npl3 associates with telomeres in an R-loop-dependent manner, as changes in R-loop levels, for example, at short telomeres, modulate the recruitment of Npl3 to chromosome ends. Through a series of genetic and biochemical approaches, we reveal that Npl3 binds to TERRA and stabilizes R-loops at short telomeres, which in turn promotes HDR and prevents premature replicative senescence onset. This may have implications for diseases associated with excessive telomere shortening.

中文翻译：

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Npl3稳定端粒R环，以防止加速复制衰老。

必须调节端粒缩短的速率以防止过早的复制性衰老。TERRA R环在关键的短端粒上变得稳定，以通过同源直接修复（HDR）促进其伸长，从而抵消了衰老的开始。使用非偏态蛋白质组学方法检测端粒结合因子，我们鉴定了Npl3，一种先前与多种RNA生物发生过程有关的RNA结合蛋白。使用染色质免疫沉淀和RNA免疫沉淀，我们证明Npl3与TERRA和端粒相互作用。此外，我们显示，Npl3以依赖于R环的方式与端粒相关联，因为R环水平的变化（例如在短端粒处）调节Npl3募集到染色体末端。通过一系列的遗传和生化方法，我们发现Npl3结合到TERRA并稳定短端粒的R环，进而促进HDR并防止过早的复制衰老发作。这可能对与端粒过度缩短有关的疾病有影响。