清华大学Jun-Jie Gogo Liu和Jia Wang共同合作，近期取得重要工作进展。他们研究开发出了小巧的Casπ（Cas12l）“手环”可以为DNA操作提供独特的结构平台。相关研究成果2023年1月17日在线发表于《细胞研究》杂志上。

据介绍，CRISPR-Cas模块作为原核生物的自适应核酸免疫系统，并为各种生物的核酸操作提供了通用的多功能工具。

研究人员从环境宏基因组中发现了一个新的微型V型系统，CRISPR Casπ（Cas12l）（约860 aa）。Casπ（Cas12l）与由包含tracrRNA和crRNA组成的大引导RNA（~170nt）复合，在广泛的生物化学条件下识别独特的5′C-富集PAM，用于DNA切割，并在哺乳动物细胞中产生基因编辑。冷冻电镜研究揭示了Casπ效应器在3.4 Å分辨率下环绕DNA靶标的“手环”结构，与Cas12和Cas9核酸酶的典型“双叶”结构有很大不同。大的引导RNA作为效应器组装的“双臂”支架。

总之，这一研究扩展了CRISPR效应器对DNA靶向机制的知识，并为DNA操作提供了一个高效但小巧的平台。

附：英文原文

Title: The compact Casπ (Cas12l) ‘bracelet’ provides a unique structural platform for DNA manipulation

Author: Sun, Ao, Li, Cheng-Ping, Chen, Zhihang, Zhang, Shouyue, Li, Dan-Yuan, Yang, Yun, Li, Long-Qi, Zhao, Yuqian, Wang, Kaichen, Li, Zhaofu, Liu, Jinxia, Liu, Sitong, Wang, Jia, Liu, Jun-Jie Gogo

Issue&Volume: 2023-01-17

Abstract: CRISPR-Cas modules serve as the adaptive nucleic acid immune systems for prokaryotes, and provide versatile tools for nucleic acid manipulation in various organisms. Here, we discovered a new miniature type V system, CRISPR-Casπ (Cas12l) (~860 aa), from the environmental metagenome. Complexed with a large guide RNA (~170 nt) comprising the tracrRNA and crRNA, Casπ (Cas12l) recognizes a unique 5′ C-rich PAM for DNA cleavage under a broad range of biochemical conditions, and generates gene editing in mammalian cells. Cryo-EM study reveals a ‘bracelet’ architecture of Casπ effector encircling the DNA target at 3.4 resolution, substantially different from the canonical ‘two-lobe’ architectures of Cas12 and Cas9 nucleases. The large guide RNA serves as a ‘two-arm’ scaffold for effector assembly. Our study expands the knowledge of DNA targeting mechanisms by CRISPR effectors, and offers an efficient but compact platform for DNA manipulation.

DOI: 10.1038/s41422-022-00771-2

Source: https://www.nature.com/articles/s41422-022-00771-2