该研究团队发现DRT3由两个不同的RTs （Drt3a和Drt3b）和一个非编码RNA （ncRNA）组成，可以合成交替的多（GT/AC）双链DNA。低温电子显微镜下2.6Å分辨率显示Drt3a， Drt3b和ncRNA的d3对称6:6:6复合体。Drt3a在ncRNA内产生poly（GT）链，使保守的ACACAC模板成为主题。值得注意的是，Drt3b在完全没有核酸模板的情况下合成了互补的蛋白引物聚链（AC），将Drt3b特异性的保守活性位点残基进行主题化，以加强精确的碱基交替。这些发现扩展了核酸聚合酶的功能景观，揭示了序列特异性DNA合成的蛋白质模板机制。
研究人员表示，防御相关逆转录酶（DRTs）是广泛存在的细菌抗噬菌体系统，其主题是多核苷酸合成的非常规机制。
附：英文原文
Title: Protein-templated synthesis of dinucleotide repeat DNA by an antiphage reverse transcriptase
Author: Pujuan Deng, Hyunbin Lee, Carlo Armijo, Haoqing Wang, Alex Gao
Issue&Volume: 2026-04-16
Abstract: Defense-associated reverse transcriptases (DRTs) are widespread bacterial anti-phage systems that use unconventional mechanisms of polynucleotide synthesis. We show that DRT3, which comprises two distinct RTs (Drt3a and Drt3b) and a noncoding RNA (ncRNA), synthesizes alternating poly(GT/AC) double-stranded DNA. Cryo–electron microscopy structures at 2.6 resolution reveal a D3-symmetric 6:6:6 complex of Drt3a, Drt3b, and ncRNA. Drt3a produces the poly(GT) strand using a conserved ACACAC template within the ncRNA. Notably, Drt3b synthesizes a complementary, protein-primed poly(AC) strand in the complete absence of a nucleic acid template, using conserved active site residues specific to Drt3b to enforce precise base alternation. These findings expand the functional landscape of nucleic acid polymerases, revealing a protein-templated mechanism for sequence-specific DNA synthesis.
DOI: aed1656
Source: https://www.science.org/doi/10.1126/science.aed1656