Target DNA structure plays a critical role in Tn7 transposition

AUTOR(ES)

Kuduvalli, Prasad N.

FONTE

Oxford University Press

RESUMO

The bacterial transposon Tn7 utilizes four Tn7-encoded proteins, TnsA, TnsB, TnsC and TnsD, to make insertions at a specific site termed attTn7. This target is selected by the binding of TnsD to attTn7 in a sequence-specific manner, followed by the binding of TnsC and activation of the transposase. We show that TnsD binding to attTn7 induces a distortion at the 5′ end of the binding site and TnsC contacts the region of attTn7 distorted by TnsD. Previous work has shown that a target site containing triplex DNA, instead of TnsD–attTn7, can recruit TnsABC and effect site- specific insertion of Tn7. We propose that the DNA distortion imposed by TnsD on attTn7, like the altered DNA structure via triplex formation, serves as a signal to recruit TnsC. We also show that TnsD primarily contacts the major groove of DNA, whereas TnsC is a minor groove binding protein. The footprint of the TnsC–TnsD–attTn7 nucleoprotein complex includes and extends beyond the Tn7 insertion site, where TnsC forms a platform to receive and activate the transposase to carry out recombination.

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