ジャーナル: Nat Struct Mol Biol / 年: 2022 タイトル: Structural basis for DNA targeting by the Tn7 transposon. 著者: Yao Shen / Josue Gomez-Blanco / Michael T Petassi / Joseph E Peters / Joaquin Ortega / Alba Guarné / 要旨: Tn7 transposable elements are unique for their highly specific, and sometimes programmable, target-site selection mechanisms and precise insertions. All the elements in the Tn7 family utilize an AAA+ ...Tn7 transposable elements are unique for their highly specific, and sometimes programmable, target-site selection mechanisms and precise insertions. All the elements in the Tn7 family utilize an AAA+ adaptor (TnsC) to coordinate target-site selection with transpososome assembly and to prevent insertions at sites already containing a Tn7 element. Owing to its multiple functions, TnsC is considered the linchpin in the Tn7 element. Here we present the high-resolution cryo-EM structure of TnsC bound to DNA using a gain-of-function variant of the protein and a DNA substrate that together recapitulate the recruitment to a specific DNA target site. TnsC forms an asymmetric ring on target DNA that segregates target-site selection and interaction with the paired-end complex to opposite faces of the ring. Unlike most AAA+ ATPases, TnsC uses a DNA distortion to find the target site but does not remodel DNA to activate transposition. By recognizing pre-distorted substrates, TnsC creates a built-in regulatory mechanism where ATP hydrolysis abolishes ring formation proximal to an existing element. This work unveils how Tn7 and Tn7-like elements determine the strict spacing between the target and integration sites.