Synapsis of Tn3 recombination sites: unpaired sites destabilize synapses by a partner exchange mechanism.
Catalysis of site-specific recombination is preceded by the formation of a synapse comprising two DNA sites and multiple subunits of the recombinase, together with other "accessory" proteins in some cases. We investigated the stability of synapses of Tn3 resolvase-bound res recombination sites, in plasmids containing either two or three res sites. Although synapses are long-lived in plasmids with just two res sites, persisting for tens of minutes, a synapse of any two sites is relatively short-lived in plasmids with three res sites. The three alternative pairwise synapses that can be formed in three-res plasmids re-assort rapidly relative to the rate of recombination. We propose a "partner exchange" mechanism for this re-assortment, involving direct attack on a synapse by an unpaired res site. This mechanism reconciles studies on selective synapsis in multi-res substrates, which imply rapid interchange of synaptic pairings, with studies indicating that synapses of two Tn3res sites are stable.
He
Jiuya
J
Institute of Biomedical and Life Sciences, University of Glasgow, 56 Dumbarton Road, Glasgow G11 6NU, Scotland, UK.
McIlwraith
Michael J
MJ
Burke
Mary E
ME
Boocock
Martin R
MR
Stark
W Marshall
WM
D001483:Base Sequence; D001665:Binding Sites; D003434:Crossing Over, Genetic / Q000235:genetics; D004251:DNA Transposable Elements / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000378:metabolism; D009690:Nucleic Acid Conformation; D010957:Plasmids / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D045522:Recombinases; D011995:Recombination, Genetic / Q000235:genetics*; D012091:Repetitive Sequences, Nucleic Acid / Q000235:genetics; D013379:Substrate Specificity; D013698:Templates, Genetic; D019895:Transposases / Q000378:metabolism; D045564:Transposon Resolvases
D004251:DNA Transposable Elements; D004268:DNA-Binding Proteins; D045522:Recombinases; C473491:Tn3 resolvase; D019895:Transposases; D045564:Transposon Resolvases