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Tn 5 transposase loops DNA in the absence of Tn 5 transposon end sequences
Author(s) -
Adams Christian D.,
Schnurr Bernhard,
Skoko Dunja,
Marko John F.,
Reznikoff William S.
Publication year - 2006
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2006.05471.x
Subject(s) - biology , transposase , transposable element , genetics , dna transposable elements , dna , p element , insertion sequence , computational biology , genome , gene
Summary Transposases mediate transposition first by binding specific DNA end sequences that define a transposable element and then by organizing protein and DNA into a highly structured and stable nucleoprotein ‘synaptic’ complex. Synaptic complex assembly is a central checkpoint in many transposition mechanisms. The Tn 5 synaptic complex contains two Tn 5 transposase subunits and two Tn 5 transposon end sequences, exhibits extensive protein–end sequence DNA contacts and is the node of a DNA loop. Using single‐molecule and bulk biochemical approaches, we found that Tn 5 transposase assembles a stable nucleoprotein complex in the absence of Tn 5 transposon end sequences. Surprisingly, this end sequence‐independent complex has structural similarities to the synaptic complex. This complex is the node of a DNA loop; transposase dimerization and DNA specificity mutants affect its assembly; and it likely has the same number of proteins and DNA molecules as the synaptic complex. Furthermore, our results indicate that Tn 5 transposase preferentially binds and loops a subset of non‐Tn 5 end sequences. Assembly of end sequence‐independent nucleoprotein complexes likely plays a role in the in vivo downregulation of transposition and the cis ‐transposition bias of many bacterial transposases.