The RepA protein of plasmid pSC101 controls Escherichia coli cell divisionthrough the SOS response

Citation
H. Ingmer et al., The RepA protein of plasmid pSC101 controls Escherichia coli cell divisionthrough the SOS response, MOL MICROB, 42(2), 2001, pp. 519-526
Citations number
54
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Microbiology
Journal title
MOLECULAR MICROBIOLOGY
ISSN journal
0950-382X → ACNP
Volume
42
Issue
2
Year of publication
2001
Pages
519 - 526
Database
ISI
SICI code
0950-382X(200110)42:2<519:TRPOPP>2.0.ZU;2-1
Abstract
Although plasmid copy number varies widely among different plasmid species, normally copy number is maintained within a narrow range for any given pla smid. Such copy number control has been shown to occur by regulation of the rate of plasmid DNA replication. Here we report a novel mechanism by which the pSC101 plasmid also can detect an imbalance between the cellular level of its replication protein, RepA, and plasmid-borne RepA binding sites to inhibit bacterial DNA replication and delay host cell division when RepA is in relative excess. We show that delayed cell division occurs by RepA-medi ated induction of the SOS response and can be reversed by overexpression of the host DNA primase, DnaG. The effects of RepA excess are prevented by in troducing a surfeit of RepA binding sites. The mechanism reported here may help to limit variation in plasmid copy number and allow repopulation of ce lls with plasmids when copy number falls - potentially pre-empting plasmid loss in cultures of dividing cells.