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Autonomous plasmid‐like replication of a conjugative transposon
Author(s) -
Lee Catherine A.,
Babic Ana,
Grossman Alan D.
Publication year - 2010
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.2009.06985.x
Subject(s) - biology , pre replication complex , dnab helicase , plasmid , genetics , minichromosome maintenance , control of chromosome duplication , origin of replication , dna replication , helicase , dna , gene , rna
Summary Integrative and conjugative elements (ICEs), a.k.a. conjugative transposons, are mobile genetic elements involved in many biological processes, including pathogenesis, symbiosis and the spread of antibiotic resistance. Unlike conjugative plasmids that are extra‐chromosomal and replicate autonomously, ICEs are integrated in the chromosome and replicate passively during chromosomal replication. It is generally thought that ICEs do not replicate autonomously. We found that when induced, Bacillus subtilis ICE Bs1 undergoes autonomous plasmid‐like replication. Replication was unidirectional, initiated from the ICE Bs1 origin of transfer, oriT , and required the ICE Bs1 ‐encoded relaxase NicK. Replication also required several host proteins needed for chromosomal replication, but did not require the replicative helicase DnaC or the helicase loader protein DnaB. Rather, replication of ICE Bs1 required the helicase PcrA that is required for rolling circle replication of many plasmids. Transfer of ICE Bs1 from the donor required PcrA, but did not require replication, indicating that PcrA, and not DNA replication, facilitates unwinding of ICE Bs1 DNA for horizontal transfer. Although not needed for horizontal transfer, replication of ICE Bs1 was needed for stability of the element. We propose that autonomous plasmid‐like replication is a common property of ICEs and contributes to the stability and maintenance of these mobile genetic elements in bacterial populations.