Three-Dimensional Structure of the Tn 5 Synaptic Complex Transposition Intermediate

Abstract

Genomic evolution has been profoundly influenced by DNA transposition, a process whereby defined DNA segments move freely about the genome. Transposition is mediated by transposases, and similar events are catalyzed by retroviral integrases such as human immunodeficiency virus-1 (HIV-1) integrase. Understanding how these proteins interact with DNA is central to understanding the molecular basis of transposition. We report the three-dimensional structure of prokaryotic Tn5 transposase complexed with Tn5 transposon end DNA determined to 2.3 angstrom resolution. The molecular assembly is dimeric, where each double-stranded DNA molecule is bound by both protein subunits, orienting the transposon ends into the active sites. This structure provides a molecular framework for understanding many aspects of transposition, including the binding of transposon end DNA by one subunit and cleavage by a second, cleavage of two strands of DNA by a single active site via a hairpin intermediate, and strand transfer into target DNA.

Reorganization of the Mu Transpososome Active Sites during a Cooperative Transition between DNA Cleavage and Joining

“…However, in this early model, reuse of the same active site for 3Ј end cleavage and joining is accomplished by moving the transposon DNA ends and by fixing the catalytic divalent metal ions and amino acids that activate the scissile phosphate. In the recent crystal structure of the related Tn5 transpososome, numerous protein-DNA contacts between transposase subunits and the transposon DNA ends are observed (21). Our model (Model 1) therefore suggests that the Mu transposon DNA ends are relatively fixed between the cleavage and joining states but that the catalytic divalent metal ions are reorganized around each scissile phosphate.…”

“…Within the Mu transpososome, the two "catalytic" subunits are arranged such that the subunit bound site-specifically to one Mu DNA end donates DDE residues for recombination of the partner Mu DNA end (23)(24)(25)28). This "criss-crossing" subunit geometry is also observed in the Tn5 transposase-DNA cocrystal (21,27) and could be a conserved feature of transposase/integrase complexes.…”

Crystal structures of catalytic core domain of BIV integrase: implications for the interaction between integrase and target DNA

“…DNA transposase is the recombinase that is most related to integrase (Czyz et al, 2007;Reznikoff, 2008). The crystal structure of prokaryotic Tn5 transposase complexed with Tn5 transposon end DNA has been solved, and it revealed that the active site of the dimer was arranged in the face-to-face mode and that the target DNA presumably bound in the middle of the dimer (Davies et al, 2000). The most recent crystal structure of eukaryotic Mos1 transposase in complex with transposon end DNA also showed face-to-face dimeric active sites.…”

Visualizing Mu transposition: assembling the puzzle pieces

“…For instance, it is important to the health of the transposon that the catalytic events at its two ends be coordinated. Biochemical experiments on Mu followed by structural studies of Tn5 transposase showed that this can be enforced by catalysis in trans (Aldaz et al 1996;Savilahti and Mizuuchi 1996;Davies et al 2000). Tight, specific binding of the transposase to the sequences near the transposon ends is accomplished not by the active-site domain itself but by one or more additional DNA-binding domains.…”