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The Leptospira interrogans lexA gene is not autoregulated
Jordi Cuñé1, Paul Cullen, Gerard Mazon
1Department of Genetics and Microbiology, Universitat Autònoma de Barcelona, Bellaterra, 08193 Barcelona, Spain.
Journal of Bacteriology
|August 4, 2005
Summary
Leptospira interrogans LexA protein binds the recA promoter but not its own lexA promoter. This finding indicates the leptospiral lexA gene is not autoregulated, unlike in other organisms.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- The SOS response is a crucial DNA repair mechanism in bacteria.
- LexA is a key transcriptional repressor regulating the SOS response in many species.
- Autoregulation of the lexA gene is a conserved feature of the SOS response.
Purpose of the Study:
- To investigate the DNA binding activity of Leptospira interrogans LexA.
- To determine if the lexA gene in L. interrogans is autoregulated.
- To identify LexA-controlled genes in L. interrogans.
Main Methods:
- Electrophoretic mobility shift assays (EMSA) and DNase I footprinting were used to assess LexA binding.
- Site-directed mutagenesis was employed to confirm binding sites.
- In silico analysis of the L. interrogans genome was performed to identify potential LexA targets.
Main Results:
- Leptospira interrogans LexA specifically binds to the palindrome TTTGN(5)CAAA in the recA promoter.
- LexA binding was not detected in the lexA promoter region.
- In silico analysis revealed no other canonical SOS genes are directly regulated by LexA.
Conclusions:
- The lexA gene in Leptospira interrogans is not autoregulated.
- This represents the first described instance of a non-autoregulated lexA gene in bacteria.
- LexA's regulatory role in L. interrogans may differ significantly from other bacterial species.