Preventing Broken Borrelia Telomeres: ResT COUPLES DUAL HAIRPIN TELOMERE FORMATION WITH PRODUCT RELEASE

Julien Briffotaux,Kerri Kobryn

doi:10.1074/jbc.m110.150060

Julien Briffotaux, Kerri Kobryn

Open Access

https://doi.org/10.1074/jbc.m110.150060

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Abstract

Spirochetes of the genus Borrelia include the tick-transmitted causative agents of Lyme disease and relapsing fever. They possess unusual genomes composed mainly of linear replicons terminated by closed DNA hairpins. Hairpin telomeres are formed from inverted repeat replicated telomere junctions (rTels) by the telomere resolvase ResT. ResT uses a reaction mechanism similar to that of the type IB topoisomerases and tyrosine recombinases. ResT can catalyze three distinct reactions: telomere resolution, telomere fusion, and Holliday junction (HJ) formation. HJ formation is known to occur only in the context of a synapsed pair of rTels. To test whether telomere resolution was synapsis-dependent, we performed experiments with rTel substrates immobilized on streptavidin-coated beads. We report that telomere resolution by ResT is synapsis-independent, indicating that alternative complexes are formed for telomere resolution and HJ formation. We also present evidence that dual hairpin telomere formation precedes product release. This mechanism of telomere resolution prevents the appearance of broken telomeres. We compare and contrast this mechanism with that proposed for TelK, the telomere resolvase of ϕKO2.

Highlights

Spirochetes of the genus Borrelia include important tick transmitted zoonotic pathogens that cause Lyme disease and relapsing fever maladies [1,2,3,4,5]
Mother and daughter DNA molecules are covalently linked via the replicated telomere junctions (rTels) junctions, which must be resolved by a specialized DNA breakage and reunion reaction, referred to as telomere resolution, that reforms the hairpin telomeres to allow for subsequent segregation
It has been unclear whether ResT could form alternative dimeric, unsynapsed, and synapsed tetrameric complexes to catalyze the telomere resolution and Holliday junction (HJ) formation reactions, respectively, or whether both reactions occur in a complex with two synapsed rTels and a tetramer of ResT

Summary

Preventing Broken Borrelia Telomeres

Spirochetes of the genus Borrelia include the tick-transmitted causative agents of Lyme disease and relapsing fever They possess unusual genomes composed mainly of linear replicons terminated by closed DNA hairpins. The reaction of all characterized tyrosine recombinases proceeds via synapsis of the two recombining sites mediated by an enzyme tetramer; cleavage and strand exchange of the equivalent strand in each duplex forms a Holliday junction (HJ). Features a tetramer of ResT acting on two rTels in a synaptic complex It is in the context of this synapse that the 4-fold DNA cleavage and hairpin formation reactions occur. In this model, synapsis is only required to activate reaction chemistry that proceeds as in Model I. The prototypical tyrosine recombinase, ␭ integrase, has been reported to produce DNA hairpins (and three-way junctions) from reaction with certain modified HJs [12, 37]

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RESULTS

DISCUSSION