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Probing plasmid partition with centromere‐based incompatibility
Author(s) -
Bouet JeanYves,
Rech Jérôme,
Egloff Sylvain,
Biek Donald P.,
Lane David
Publication year - 2005
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.1365-2958.2004.04396.x
Subject(s) - centromere , plasmid , biology , low copy number , pairing , genetics , partition (number theory) , microbiology and biotechnology , gene , chromosome , superconductivity , physics , quantum mechanics , mathematics , combinatorics
Summary Low‐copy number plasmids of bacteria rely on specific centromeres for regular partition into daughter cells. When also present on a second plasmid, the centromere can render the two plasmids incompatible, disrupting partition and causing plasmid loss. We have investigated the basis of incompatibility exerted by the F plasmid centromere, sopC , to probe the mechanism of partition. Measurements of the effects of sopC at various gene dosages on destabilization of mini‐F, on repression of the sopAB operon and on occupancy of mini‐F DNA by the centromere‐binding protein, SopB, revealed that among mechanisms previously proposed, no single one fully explained incompatibility. sopC on multicopy plasmids depleted SopB by titration and by contributing to repression. The resulting SopB deficit is proposed to delay partition complex formation and facilitate pairing between mini‐F and the centromere vector, thereby increasing randomization of segregation. Unexpectedly, sopC on mini‐P1 exerted strong incompatibility if the P1 parABS locus was absent. A mutation preventing the P1 replication initiation protein from pairing (handcuffing) reduced this strong incompatibility to the level expected for random segregation. The results indicate the importance of kinetic considerations and suggest that mini‐F handcuffing promotes pairing of SopB– sopC complexes that can subsequently segregate as intact aggregates.