DnaC inactivation in Escherichia coli K-12 induces the SOS response and expression of nucleotide biosynthesis genes

TY - JOUR

T1 - DnaC inactivation in Escherichia coli K-12 induces the SOS response and expression of nucleotide biosynthesis genes

AU - Løbner-Olesen, Anders

AU - Slominska-Wojewodzka, Monika

AU - Hansen, Flemming G

AU - Marinus, Martin G

PY - 2008/8/20

Y1 - 2008/8/20

N2 - 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.METHODOLOGY/PRINCIPAL FINDINGS: 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.CONCLUSION/SIGNIFICANCE: 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.

AB - 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.METHODOLOGY/PRINCIPAL FINDINGS: 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.CONCLUSION/SIGNIFICANCE: 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.

KW - Bacterial Proteins/genetics

KW - Chromosomes, Bacterial/genetics

KW - DNA Replication/genetics

KW - DNA-Binding Proteins/genetics

KW - Escherichia coli K12/genetics

KW - Escherichia coli Proteins/antagonists & inhibitors

KW - Flow Cytometry

KW - Gene Expression Profiling

KW - Gene Expression Regulation, Bacterial

KW - Genes, Bacterial

KW - Genes, Lethal

KW - Heat-Shock Proteins/genetics

KW - Nucleotides/biosynthesis

KW - Oligonucleotide Array Sequence Analysis

KW - RNA, Bacterial/genetics

KW - RNA, Messenger/genetics

KW - SOS Response (Genetics)

KW - Thermodynamics

KW - Transcription, Genetic

U2 - 10.1371/journal.pone.0002984

DO - 10.1371/journal.pone.0002984

M3 - Journal article

C2 - 18714349

SN - 1932-6203

VL - 3

SP - e2984

JO - PLoS Computational Biology

JF - PLoS Computational Biology

IS - 8

ER -