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<p>In the evolutionary arms race between bacteria and viruses, retrons have emerged as distinctive antiphage defense systems. Here, we elucidate the structure and function of Retron-Eco2, which comprises a non-coding RNA (ncRNA) that encodes multicopy single-stranded DNA (msDNA, a DNA‒RNA hybrid) and a fusion protein containing a reverse transcriptase (RT) domain and a topoisomerase-primase-like (Toprim) effector domain. The Eco2 msDNA and RT-Toprim fusion protein form a 1:1 stoichiometric nucleoprotein complex that further assembles into a trimer (msDNA:RT-Toprim ratio of 3:3) with a distinctive triangular configuration. The RNA portion of the msDNA in one protomer closely intertwines around the RT domain of an adjacent protomer, mediating the formation of this self-inhibitory assembly. Upon activation, the Toprim effector domain exhibits RNase activity, degrading RNA to arrest phage replication. We further reveal that phage mutants evading Eco2-mediated defense harbor mutations in the endonuclease IV-like protein DenB, underscoring DenB’s critical role in triggering the activation of this system. Together, these findings provide key structural and functional insights into Retron-Eco2, laying the groundwork for harnessing its potential in biotechnology and synthetic biology applications.</p>

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Structural basis of the RNA-mediated Retron-Eco2 oligomerization

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2025年9月2日

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  • Yanjing Wang,
  • Chen Wang,
  • Yongqi Yin,
  • Yongqing Cui,
  • Zhikang Dai,
  • Chang Liu,
  • Yanke Chen,
  • Zeyuan Guan,
  • Tingting Zou

摘要

In the evolutionary arms race between bacteria and viruses, retrons have emerged as distinctive antiphage defense systems. Here, we elucidate the structure and function of Retron-Eco2, which comprises a non-coding RNA (ncRNA) that encodes multicopy single-stranded DNA (msDNA, a DNA‒RNA hybrid) and a fusion protein containing a reverse transcriptase (RT) domain and a topoisomerase-primase-like (Toprim) effector domain. The Eco2 msDNA and RT-Toprim fusion protein form a 1:1 stoichiometric nucleoprotein complex that further assembles into a trimer (msDNA:RT-Toprim ratio of 3:3) with a distinctive triangular configuration. The RNA portion of the msDNA in one protomer closely intertwines around the RT domain of an adjacent protomer, mediating the formation of this self-inhibitory assembly. Upon activation, the Toprim effector domain exhibits RNase activity, degrading RNA to arrest phage replication. We further reveal that phage mutants evading Eco2-mediated defense harbor mutations in the endonuclease IV-like protein DenB, underscoring DenB’s critical role in triggering the activation of this system. Together, these findings provide key structural and functional insights into Retron-Eco2, laying the groundwork for harnessing its potential in biotechnology and synthetic biology applications.