小柯机器人

美国普渡大学Leifu Chang研究小组揭示I-B型CRISPR效应器招募Tn7样转座子的分子机制。2023年8月8日，国际知名学术期刊《细胞》在线发表了这一成果。

研究人员表示，Tn7样转座子与CRISPR-Cas系统合作，促进了自身DNA的移动。这些CRISPR相关转座子（CAST）是可编程基因敲除的有望工具。CAST的一个主要特点是能够将Tn7样转座子招募到核酸酶缺陷的CRISPR效应器上。然而，人们对Tn7样转座子是如何被不同的CRISPR效应器招募的仍然知之甚少。

研究人员展示了由Cascade复合物、TniQ、TnsC和来自Peltigera membranacea cyanobiont 210A的I-B型CAST中的靶标DNA组成的招募复合物冷冻电镜结构。Cascade对靶标DNA的识别会诱导Cas6发生构象变化，并通过其C端结构域启动TniQ的招募。TniQ的N端结构域与TnsC螺旋七聚体的接缝区域结合。这项发现让人们深入了解了Tn7样转座子招募到CRISPR效应器的不同机制，并将有助于开发CAST作为基因敲除工具。

附：英文原文

Title: Molecular mechanism for Tn7-like transposon recruitment by a type I-B CRISPR effector

Author: Shukun Wang, Clinton Gabel, Romana Siddique, Thomas Klose, Leifu Chang

Issue&Volume: 2023-08-08

Abstract: Tn7-like transposons have co-opted CRISPR-Cas systems to facilitate the movement oftheir own DNA. These CRISPR-associated transposons (CASTs) are promising tools forprogrammable gene knockin. A key feature of CASTs is their ability to recruit Tn7-liketransposons to nuclease-deficient CRISPR effectors. However, how Tn7-like transposonsare recruited by diverse CRISPR effectors remains poorly understood. Here, we presentthe cryo-EM structure of a recruitment complex comprising the Cascade complex, TniQ,TnsC, and the target DNA in the type I-B CAST from Peltigera membranacea cyanobiont 210A. Target DNA recognition by Cascade induces conformational changes in Cas6 and primesTniQ recruitment through its C-terminal domain. The N-terminal domain of TniQ is boundto the seam region of the TnsC spiral heptamer. Our findings provide insights intothe diverse mechanisms for the recruitment of Tn7-like transposons to CRISPR effectorsand will aid in the development of CASTs as gene knockin tools.

DOI: 10.1016/j.cell.2023.07.010

Source: https://www.cell.com/cell/fulltext/S0092-8674(23)00743-2