Song Xin-Yi, Xia Yushan, Zhang Jun-Tao, Liu Yu-Jun, Qi Hua, Wei Xin-Yang, Hu Hailiang, Xia Yu, Liu Xue, Ma Ying-Fei, Jia Ning
Department of Biochemistry, SUSTech Homeostatic Medicine Institute, School of Medicine, Southern University of Science and Technology, Shenzhen, China.
School of Environmental Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, China.
Science. 2025 May 1:eads4639. doi: 10.1126/science.ads4639.
Prokaryotic defense-associated reverse transcriptases (DRTs) were recently identified with antiviral functions; however, their functional mechanisms remain largely unexplored. Here we show that DRT9 forms a hexameric complex with its upstream non-coding RNA (ncRNA) to mediate antiphage defense by inducing cell growth arrest via abortive infection. Upon phage infection, the phage-encoded ribonucleotide reductase NrdAB complex elevates intracellular dATP levels, activating DRT9 to synthesize long, poly-A-rich single-stranded cDNA, which likely sequesters the essential phage SSB protein and disrupts phage propagation. We further determined the cryo-electron microscopy structure of the DRT9-ncRNA hexamer complex, providing mechanistic insights into its cDNA synthesis. These findings highlight the diversity of RT-based antiviral defense mechanisms, expand our understanding of RT biological functions, and provide a structural basis for developing DRT9-based biotechnological tools.
原核生物防御相关逆转录酶（DRTs）最近被鉴定出具有抗病毒功能；然而，它们的功能机制在很大程度上仍未被探索。在这里，我们表明DRT9与其上游非编码RNA（ncRNA）形成六聚体复合物，通过流产感染诱导细胞生长停滞来介导抗噬菌体防御。噬菌体感染后，噬菌体编码的核糖核苷酸还原酶NrdAB复合物提高细胞内dATP水平，激活DRT9以合成长的、富含多聚A的单链cDNA，这可能会隔离必需的噬菌体单链结合蛋白（SSB）并破坏噬菌体繁殖。我们进一步确定了DRT9-ncRNA六聚体复合物的冷冻电镜结构，为其cDNA合成提供了机制性见解。这些发现突出了基于逆转录酶的抗病毒防御机制的多样性，扩展了我们对逆转录酶生物学功能的理解，并为开发基于DRT9的生物技术工具提供了结构基础。
