DnaC inactivation in Escherichia coli K-12 induces the SOS response and expression of nucleotide biosynthesis genes.
BACKGROUND
Initiation of chromosome replication in E. coli requires the DnaA and DnaC proteins and conditionally-lethal dnaA and dnaC mutants are often used to synchronize cell populations.


RESULTS
DNA microarrays were used to measure mRNA steady-state levels in initiation-deficient dnaA46 and dnaC2 bacteria at permissive and non-permissive temperatures and their expression profiles were compared to MG1655 wildtype cells. For both mutants there was altered expression of genes involved in nucleotide biosynthesis at the non-permissive temperature. Transcription of the dnaA and dnaC genes was increased at the non-permissive temperature in the respective mutant strains indicating auto-regulation of both genes. Induction of the SOS regulon was observed in dnaC2 cells at 38 degrees C and 42 degrees C. Flow cytometric analysis revealed that dnaC2 mutant cells at non-permissive temperature had completed the early stages of chromosome replication initiation.


CONCLUSIONS
We suggest that in dnaC2 cells the SOS response is triggered by persistent open-complex formation at oriC and/or by arrested forks that require DnaC for replication restart.
Løbner-Olesen
Anders
A
Department of Science, Systems and Models, Roskilde University, Roskilde, Denmark.
Slominska-Wojewodzka
Monika
M
Hansen
Flemming G
FG
Marinus
Martin G
MG
D001426:Bacterial Proteins / Q000235:genetics; D002876:Chromosomes, Bacterial / Q000235:genetics; D004261:DNA Replication / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics; D048168:Escherichia coli K12 / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics; D005434:Flow Cytometry; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D005804:Genes, Lethal; D006360:Heat-Shock Proteins / Q000235:genetics; D009711:Nucleotides / Q000096:biosynthesis / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D012329:RNA, Bacterial / Q000235:genetics / Q000302:isolation & purification; D012333:RNA, Messenger / Q000235:genetics; D013014:SOS Response, Genetics; D013816:Thermodynamics; D014158:Transcription, Genetic
D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C066312:DnaA protein, Bacteria; C071702:DnaC protein, E coli; D029968:Escherichia coli Proteins; D006360:Heat-Shock Proteins; D009711:Nucleotides; D012329:RNA, Bacterial; D012333:RNA, Messenger