system
Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: BACKGROUND, RESULTS. Meshes: Bacterial Proteins, Chromosomes, Bacterial, DNA Replication, DNA-Binding Proteins, Escherichia coli K12, Escherichia coli Proteins, Flow Cytometry, Gene Expression Profiling, Gene Expression Regulation, Bacterial, Genes, Bacterial, Genes, Lethal, Heat-Shock Proteins, Nucleotides, Oligonucleotide Array Sequence Analysis, RNA, Bacterial, RNA, Messenger, SOS Response (Genetics), Thermodynamics, Transcription, Genetic.
user
Does dnaC inactivation in Escherichia coli K-12 induce the SOS response and expression of nucleotide biosynthesis genes? Context: 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. 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.
assistant
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. Final Decision: yes