Bacillus subtilis RecA interacts with and loads RadA/Sms to unwind recombination intermediates during natural chromosomal transformation

Torres, R., Serrano, E. and Alonso, J. C. (2019) Bacillus subtilis RecA interacts with and loads RadA/Sms to unwind recombination intermediates during natural chromosomal transformation. Nucleic Acids Research, 47(17), pp. 9198-9215. (doi: 10.1093/nar/gkz647) (PMID:31350886) (PMCID:PMC6755099)

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Abstract

During natural transformation Bacillus subtilis RecA, polymerized onto the incoming single-stranded (ss) DNA, catalyses DNA strand invasion resulting in a displacement loop (D-loop) intermediate. A null radA mutation impairs chromosomal transformation, and RadA/Sms unwinds forked DNA in the 5′→3′ direction. We show that in the absence of RadA/Sms competent cells require the RecG translocase for natural chromosomal transformation. RadA/Sms tetracysteine motif (C13A and C13R) variants, which fail to interact with RecA, are also deficient in plasmid transformation, but this defect is suppressed by inactivating recA. The RadA/Sms C13A and C13R variants bind ssDNA, and this interaction stimulates their ATPase activity. Wild-type (wt) RadA/Sms interacts with and inhibits the ATPase activity of RecA, but RadA/Sms C13A fails to do it. RadA/Sms and its variants, C13A and C13R, bound to the 5′-tail of a DNA substrate, unwind DNA in the 5′→3′ direction. RecA interacts with and loads wt RadA/Sms to promote unwinding of a non-cognate 3′-tailed or 5′-fork DNA substrate, but RadA/Sms C13A or C13R fail to do it. We propose that wt RadA/Sms interaction with RecA is crucial to recruit the former onto D-loop DNA, and both proteins in concert catalyse D-loop extension to favour integration of ssDNA during chromosomal transformation.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Serrano, Dr Ester
Authors: Torres, R., Serrano, E., and Alonso, J. C.
College/School:College of Medical Veterinary and Life Sciences > School of Infection & Immunity
Journal Name:Nucleic Acids Research
Publisher:Oxford University Press
ISSN:0305-1048
ISSN (Online):1362-4962
Published Online:27 July 2019
Copyright Holders:Copyright © 2019 The Authors
First Published:First published in Nucleic Acids Research 47(17): 9198-9215
Publisher Policy:Reproduced under a Creative Commons License

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