Bacillus subtilis MutS modulates RecA-mediated DNA strand exchange between divergent DNA sequences

Carrasco, B., Serrano, E. , Martín-González, A., Moreno-Herrero, F. and Alonso, J. C. (2019) Bacillus subtilis MutS modulates RecA-mediated DNA strand exchange between divergent DNA sequences. Frontiers in Microbiology, 10, 237. (doi: 10.3389/fmicb.2019.00237) (PMID:30814990) (PMCID:PMC6382021)

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The efficiency of horizontal gene transfer, which contributes to acquisition and spread of antibiotic resistance and pathogenicity traits, depends on nucleotide sequence and different mismatch-repair (MMR) proteins participate in this process. To study how MutL and MutS MMR proteins regulate recombination across species boundaries, we have studied natural chromosomal transformation with DNA up to ∼23% sequence divergence. We show that Bacillus subtilis natural chromosomal transformation decreased logarithmically with increased sequence divergence up to 15% in wild type (wt) cells or in cells lacking MutS2 or mismatch repair proteins (MutL, MutS or both). Beyond 15% sequence divergence, the chromosomal transformation efficiency is ∼100-fold higher in ΔmutS and ΔmutSL than in ΔmutS2 or wt cells. In the first phase of the biphasic curve (up to 15% sequence divergence), RecA-catalyzed DNA strand exchange contributes to the delineation of species, and in the second phase, homology-facilitated illegitimate recombination might aid in the restoration of inactivated genes. To understand how MutS modulates the integration process, we monitored DNA strand exchange reactions using a circular single-stranded DNA and a linear double-stranded DNA substrate with an internal 77-bp region with ∼16% or ∼54% sequence divergence in an otherwise homologous substrate. The former substrate delayed, whereas the latter halted RecA-mediated strand exchange. Interestingly, MutS addition overcame the heterologous barrier. We propose that MutS assists DNA strand exchange by facilitating RecA disassembly, and indirectly re-engagement with the homologous 5′-end of the linear duplex. Our data supports the idea that MutS modulates bidirectional RecA-mediated integration of divergent sequences and this is important for speciation.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Serrano, Dr Ester
Authors: Carrasco, B., Serrano, E., Martín-González, A., Moreno-Herrero, F., and Alonso, J. C.
College/School:College of Medical Veterinary and Life Sciences > School of Infection & Immunity
Journal Name:Frontiers in Microbiology
Publisher:Frontiers Media
ISSN (Online):1664-302X
Copyright Holders:Copyright © 2019 Carraso, Serrano, Martín-González, Moreno-Herrero and Alonso
First Published:First published in Frontiers in Microbiology 10: 237
Publisher Policy:Reproduced under a Creative Commons License

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