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bioRxiv · 10.1101/2021.05.24.445525

Structural basis for DNA targeting by the Tn7 transposon

Shen, Y.·Gomez-Blanco, J.·Petassi, M. T.·Peters, J. E.·Ortega, J.·Guarne, A.
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Abstract

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 a AAA+ adaptor (TnsC) to coordinates target-site selection with transposase activation and prevent insertions at sites already containing a Tn7 element. Due 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. We find that TnsC forms an asymmetric ring on target DNA that segregates target-site selection and transposase recruitment 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.

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Shen, Y., Gomez-Blanco, J., Petassi, M. T., Peters, J. E., Ortega, J., Guarne, A.. 2021-05-25. Structural basis for DNA targeting by the Tn7 transposon. https://doi.org/10.1101/2021.05.24.445525

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