美国普渡大学Leifu Chang研究小组发现，TnsABCD转座复合物的结构揭示靶向DNA转座的机制。该研究于2024年10月8日在线发表于国际一流学术期刊《细胞》。

研究人员展示了在Tn7类转座子Peltigera membranacea蓝藻共生体210A（一种I-B型CRISPR相关转座子）中TnsC-TnsD-att DNA复合物和TnsABCD转座复合物的冷冻电镜（cryo-EM）结构。

该结构揭示了结合位点（att）DNA的显著弯曲，特点是TnsD的精氨酸侧链插入CC/GG二核苷酸步。TnsABCD转座复合物的结构显示了TnsA-TnsB的相互作用，并表明TnsC不仅招募TnsAB，还直接参与了转座复合物的组装。

这些发现为Tn7类转座子的靶向DNA插入机制提供了见解，并对提高其基因编辑应用的精准性和效率具有重要意义。

据介绍，Tn7类转座子因其能够特异性插入宿主染色体而具有独特特点。TnsD通过识别att位点招募TnsABC蛋白形成转座复合物，从而促进转座过程。尽管这一通路已得到充分研究，但关于该过程的原子级结构信息仍然鲜为人知。

附：英文原文

Title: Structure of TnsABCD transpososome reveals mechanisms of targeted DNA transposition

Author: Shukun Wang, Romana Siddique, Mark C. Hall, Phoebe A. Rice, Leifu Chang

Issue&Volume: 2024-10-08

Abstract: Tn7-like transposons are characterized by their ability to insert specifically into host chromosomes. Recognition of the attachment (att) site by TnsD recruits the TnsABC proteins to form the transpososome and facilitate transposition. Although this pathway is well established, atomic-level structural insights of this process remain largely elusive. Here, we present the cryo-electron microscopy (cryo-EM) structures of the TnsC-TnsD-att DNA complex and the TnsABCD transpososome from the Tn7-like transposon in Peltigera membranacea cyanobiont 210A, a type I-B CRISPR-associated transposon. Our structures reveal a striking bending of the att DNA, featured by the intercalation of an arginine side chain of TnsD into a CC/GG dinucleotide step. The TnsABCD transpososome structure reveals TnsA-TnsB interactions and demonstrates that TnsC not only recruits TnsAB but also directly participates in the transpososome assembly. These findings provide mechanistic insights into targeted DNA insertion by Tn7-like transposons, with implications for improving the precision and efficiency of their genome-editing applications.

DOI: 10.1016/j.cell.2024.09.023

Source: https://www.cell.com/cell/abstract/S0092-8674(24)01071-7