Exploration of DNA processing features unravels novel properties of ICE conjugation in Gram-positive bacteria
Résumé
Integrative and conjugative elements (ICEs) are important drivers of horizontal gene transfer in prokaryotes. They are responsible for antimicrobial resistance spread, a major current health concern. ICEs are initially processed by relaxases that recognize the binding site of oriT sequence and nick at a conserved nic site. The ICESt3/Tn916/ICEBs1 superfamily, which is widespread among Firmicutes, encodes uncanonical relaxases belonging to a recently identified family called MOB T. This family is related to the rolling circle replication initiators of the Rep trans family. The nic site of these MOB T relaxases is conserved but their DNA binding site is still unknown. Here, we identified the bind site of RelSt3, the MOB T relaxase from ICESt3. Unexpectedly, we found this bind site distantly located from the nic site. We revealed that the binding of the RelSt3 N-terminal HTH domain is required for efficient nicking activity. We also deciphered the role of RelSt3 in the initial and final stages of DNA processing during conjugation. Especially, we demonstrated a strand transfer activity, and the formation of covalent DNA-relaxase intermediate for a MOB T relaxase.
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Exploration of DNA processing features unravels novel properties of ICE conjugation in Gram-positive bacteria - Laroussi et al - NAR - 2022.pdf (3.21 Mo)
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