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<p>TERRA long noncoding RNAs associate with telomeres post transcription through base-pairing with telomeric DNA forming R-loop structures. TERRA regulates telomere maintenance but its exact modes of action remain unknown. Here, we induce TERRA transcription and R-loop formation in telomerase-expressing cells and determine that TERRA R-loop formation requires non-redundant functions of the RAD51 DNA recombinase and its enhancer RAD51AP1. TERRA R-loops interfere with semiconservative DNA replication, promoting telomere maintenance by a homology-directed repair (HDR) mechanism known as break-induced replication (BIR), which ensures telomere maintenance in ALT cancer cells. In addition, TERRA induces PRIMPOL-dependent repair, which can initiate DNA synthesis de novo downstream of replication obstacles. PRIMPOL acts in parallel to BIR for telomere maintenance of TERRA-overexpressing cells, promoting their survival. Similarly, we find that PRIMPOL depletion is synthetic-lethal with BIR deficiency in U2OS ALT cancer cells. Therefore, TERRA R-loops by themselves are sufficient to induce ALT-typical telomere repair mechanisms, in the absence of other ALT-typical telomeric chromatin changes.</p>

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TERRA R-loops trigger a switch in telomere maintenance towards break-induced replication and PRIMPOL-dependent repair

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年7月7日

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  • Suna In,
  • Patricia Renck Nunes,
  • Rita Valador Fernandes,
  • Joachim Lingner

摘要

TERRA long noncoding RNAs associate with telomeres post transcription through base-pairing with telomeric DNA forming R-loop structures. TERRA regulates telomere maintenance but its exact modes of action remain unknown. Here, we induce TERRA transcription and R-loop formation in telomerase-expressing cells and determine that TERRA R-loop formation requires non-redundant functions of the RAD51 DNA recombinase and its enhancer RAD51AP1. TERRA R-loops interfere with semiconservative DNA replication, promoting telomere maintenance by a homology-directed repair (HDR) mechanism known as break-induced replication (BIR), which ensures telomere maintenance in ALT cancer cells. In addition, TERRA induces PRIMPOL-dependent repair, which can initiate DNA synthesis de novo downstream of replication obstacles. PRIMPOL acts in parallel to BIR for telomere maintenance of TERRA-overexpressing cells, promoting their survival. Similarly, we find that PRIMPOL depletion is synthetic-lethal with BIR deficiency in U2OS ALT cancer cells. Therefore, TERRA R-loops by themselves are sufficient to induce ALT-typical telomere repair mechanisms, in the absence of other ALT-typical telomeric chromatin changes.