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<p>R-loops are pervasive genomic structures that link epigenetic modification and transcriptional regulation. However, the functional roles and regulatory mechanisms of R-loops during preimplantation development in mammals remain unexplored. Here, we reveal that the reprogramming of R-loops across developmental stages depends on CG density, with CG-poor R-loops more stage specific and strongly associated with early embryonic development. Loss of CG-poor R-loops causes severe defects in the maternal-to-zygotic transition (MZT) and preimplantation embryo development. This abnormal maintenance of CG-poor R-loops promotes premature activation of major zygotic genome activation (ZGA) genes. CG-poor R-loops inhibit DDX21 helicase activity on the 7SK/HEXIM1 snRNP complex, restricting CDK9 release and subsequent phosphorylation of Ser2 at the C-terminal domain of RNA polymerase II (RNAPII S2p) — the biochemical hallmark of pause release — thus enforcing RNAPII accumulation at major ZGA gene promoters to ensure productive transcription. These findings establish R-loops as direct modulators of RNAPII pause release, promoting the temporal fidelity of gene expression during the MZT.</p>

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R-loops orchestrate RNAPII transcriptional reprogramming for the maternal-to-zygotic transition

  • 期刊论文

  • 发表日期：

    2026年1月9日

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  • Yaoyi Li,
  • Qing Li,
  • Xinxiu Wang,
  • Chao Di,
  • Yingliang Sheng,
  • Ying Ma,
  • Junzhi Liao,
  • Qingqing Cai,
  • Sainan Huang,
  • Jiayu Chen,
  • Guangming Wu,
  • Lingling Zhang,
  • Guangjin Pan,
  • Shaorong Gao,
  • Hongjie Yao

摘要

R-loops are pervasive genomic structures that link epigenetic modification and transcriptional regulation. However, the functional roles and regulatory mechanisms of R-loops during preimplantation development in mammals remain unexplored. Here, we reveal that the reprogramming of R-loops across developmental stages depends on CG density, with CG-poor R-loops more stage specific and strongly associated with early embryonic development. Loss of CG-poor R-loops causes severe defects in the maternal-to-zygotic transition (MZT) and preimplantation embryo development. This abnormal maintenance of CG-poor R-loops promotes premature activation of major zygotic genome activation (ZGA) genes. CG-poor R-loops inhibit DDX21 helicase activity on the 7SK/HEXIM1 snRNP complex, restricting CDK9 release and subsequent phosphorylation of Ser2 at the C-terminal domain of RNA polymerase II (RNAPII S2p) — the biochemical hallmark of pause release — thus enforcing RNAPII accumulation at major ZGA gene promoters to ensure productive transcription. These findings establish R-loops as direct modulators of RNAPII pause release, promoting the temporal fidelity of gene expression during the MZT.