Cryo-EM structures of Escherichia coli Ec86 retron complexes reveal architecture and defence mechanism.
Cryo-EM structures of Escherichia coli Ec86 retron complexes reveal architecture and defence mechanism.
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大肠杆菌 Ec86 逆转录子复合物的冷冻电镜结构揭示了其结构和防御机制。
DOI：
10.1038/s41564-022-01197-7
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发表时间：
2022
影响因子：
28.3
通讯作者：
Tingting Zou
中科院分区：
文献类型：
--
作者：
Yanjing Wang;Zeyuan Guan;Chen Wang;Yangfan Nie;Yibei Chen;Zhaoyang Qian;Yongqing Cui;Han Xu;Qiang Wang;Fen Zhao;Delin Zhang;Pan Tao;Ming Sun;Ping Yin;Shuangxia Jin;Shan Wu;Tingting Zou
逆转录酶最早发现于20世纪80年代，是由逆转录酶和非编码RNA （ncRNA）组成的细菌遗传元件。逆转录酶介导细菌的抗噬菌体防御，但其结构和防御机制尚不清楚。在这里，我们研究了大肠杆菌Ec86逆转录，并使用低温电子显微镜确定了Ec86 （3.1 Å）和同源效应结合的Ec86 （2.5 Å）复合物的结构。Ec86逆转录酶表现出典型的右手状折叠，由手指、手掌和拇指子结构域组成。Ec86逆转录酶将部分ncRNA逆转录成卫星，多拷贝单链DNA （msDNA，一种DNA- rna杂交），我们展示了它包裹在逆转录酶的正电表面。在msDNA中，存在两个反向重复序列，并且DNA/RNA链的3'侧靠近逆转录酶活性位点。Ec86效应物采用双叶折叠，直接结合逆转录酶和msDNA。这些发现有助于深入了解逆转录效应单元的结构-功能关系，并为基于逆转录的基因组编辑系统的优化提供结构基础。
First discovered in the 1980s, retrons are bacterial genetic elements consisting of a reverse transcriptase and a non-coding RNA (ncRNA). Retrons mediate antiphage defence in bacteria but their structure and defence mechanisms are unknown. Here, we investigate the Escherichia coli Ec86 retron and use cryo-electron microscopy to determine the structures of the Ec86 (3.1 Å) and cognate effector-bound Ec86 (2.5 Å) complexes. The Ec86 reverse transcriptase exhibits a characteristic right-hand-like fold consisting of finger, palm and thumb subdomains. Ec86 reverse transcriptase reverse-transcribes part of the ncRNA into satellite, multicopy single-stranded DNA (msDNA, a DNA-RNA hybrid) that we show wraps around the reverse transcriptase electropositive surface. In msDNA, both inverted repeats are present and the 3' sides of the DNA/RNA chains are close to the reverse transcriptase active site. The Ec86 effector adopts a two-lobe fold and directly binds reverse transcriptase and msDNA. These findings offer insights into the structure-function relationship of the retron-effector unit and provide a structural basis for the optimization of retron-based genome editing systems.