Integrative suppression of dnaA(Ts) mutations mediated by plasmid F in Escherichia coli is a DnaA-dependent process.
The thermosensitivity of dnaA(Ts) mutations can be suppressed by integration of plasmid F (integrative suppression). In the light of the recent finding that F requires DnaA protein for both establishment and maintenance, integrative suppression of 11 dnaA(Ts) mutations by a mini-F, pML31, integrated near oriC was examined. The plating efficiency of integratively suppressed strains was dnaA(Ts) allele-dependent and medium-dependent. The initiation capability of suppressed dnaA(Ts) strains lacking the oriC site and their F- counterparts was determined at various temperatures between 30 degrees C and 42 degrees C. The degree of integrative suppression measured by the initiation capability varied in a dnaA(Ts) allele-dependent manner. F-directed DNA replication was most affected by the dnaA(Ts) mutations mapping in the middle of the gene whereas oriC-dependent replication was most thermosensitive in strains carrying mutations mapping in the carboxy-terminal half of the gene. The results indicated that the integrative suppression by F plasmid is a DnaA-dependent process and suggested that the requirements for DnaA protein in the oriC-dependent replication and F replication processes are qualitatively different.
Kogoma
T
T
Department of Cell Biology, School of Medicine, University of New Mexico, Albuquerque 87131.
Kline
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BC
D001426:Bacterial Proteins / Q000235:genetics*; D004261:DNA Replication; D004269:DNA, Bacterial / Q000096:biosynthesis; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D005798:Genes, Bacterial; D009154:Mutation; D010957:Plasmids; D013489:Suppression, Genetic; D013696:Temperature
D001426:Bacterial Proteins; D004269:DNA, Bacterial