Beijing Advanced Innovation Center for Structural Biology & Frontier Research Center for Biological Structure, School of Life Sciences, Tsinghua University, Beijing, China.
Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China.
Cell Res. 2023 Mar;33(3):229-244. doi: 10.1038/s41422-022-00771-2. Epub 2023 Jan 17.
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 Å 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.
CRISPR-Cas 模块作为原核生物的适应性核酸免疫系统，为各种生物的核酸操作提供了多功能工具。在这里，我们从环境宏基因组中发现了一种新型的微型 V 型系统 CRISPR-Casπ（Cas12l）（860aa）。与包含 tracrRNA 和 crRNA 的大型向导 RNA（170nt）复合后，Casπ（Cas12l）在广泛的生化条件下识别独特的 5' C 丰富的 PAM 用于 DNA 切割，并在哺乳动物细胞中产生基因编辑。低温电子显微镜研究揭示了 Casπ 效应器的“手链”结构，以 3.4Å 的分辨率环绕 DNA 靶标，与 Cas12 和 Cas9 核酸酶的典型“双叶”结构有很大不同。大型向导 RNA 充当效应器组装的“双臂”支架。我们的研究扩展了 CRISPR 效应物的 DNA 靶向机制的知识，并提供了一种高效但紧凑的 DNA 操作平台。
