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Genetic composition of the Bacillus subtilis SOS system
Nora Au1, Elke Kuester-Schoeck, Veena Mandava
1Department of Chemistry, Williams College, Williamstown, MA 01267, USA.
Journal of Bacteriology
|November 4, 2005
Summary
Bacteria utilize the SOS response to repair DNA damage. Researchers identified 33 Bacillus subtilis genes regulated by RecA and LexA proteins, revealing a new operator sequence critical for bacterial DNA repair mechanisms.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- The SOS response is a crucial bacterial defense mechanism against DNA damage.
- This response involves the RecA protein sensing DNA damage and inactivating the LexA repressor.
- LexA inactivation leads to the expression of genes involved in DNA repair and survival.
Purpose of the Study:
- To identify genes regulated by the RecA-LexA system in Bacillus subtilis.
- To characterize the DNA binding sites and consensus sequences for LexA in B. subtilis.
- To compare the B. subtilis SOS regulon with that of Escherichia coli.
Main Methods:
- Bioinformatic analysis of the B. subtilis genome to find putative LexA binding sites.
- Electrophoretic mobility shift assays (EMSAs) to confirm LexA DNA binding.
- DNA microarray analysis to assess RecA-dependent gene induction.
- Sequence alignment to determine the consensus LexA operator sequence.
Main Results:
- Identified 62 potential LexA-regulated genes in B. subtilis.
- Confirmed LexA binding to 54 genes within 34 putative operons.
- Observed RecA-dependent induction of 33 genes by mitomycin C and UV radiation.
- Determined an expanded consensus operator sequence for B. subtilis LexA: 5'-CGAACATATGTTCG-3'.
- Found limited homology between B. subtilis and E. coli SOS genes.
Conclusions:
- Established a significant portion of the B. subtilis SOS regulon.
- Characterized the specific DNA binding motif for LexA in B. subtilis.
- Highlighted evolutionary divergence in SOS response genes between bacterial species.