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SOS response as an adaptive response to DNA damage in prokaryotes
1Department of Molecular Microbiology, Osaka University, Japan.
Abstract:
Escherichia coli possesses an elaborate adaptive mechanism called the "SOS response" to cope with various types of DNA damage. More than 20 SOS genes, most of which are known to be involved in the functions that promote the survival of DNA-damaged cells, are induced by treatments that damage DNA or inhibit DNA synthesis. All the SOS genes share similar sequences in the regulatory regions called the "SOS box", to which LexA repressor binds to repress the transcription in the absence of DNA damage. The SOS signal appears to be the single-stranded DNA produced in vicinity of DNA damage, to which RecA protein binds to be activated as a coprotease. The activated RecA promotes autocleavage of LexA protein by allosteric interaction, which activates the latent serine protease activity of LexA. The induced products of the SOS genes repair DNA lesions by various mechanisms, including recombination, excision repair and error-prone repair, and as the consequence, the SOS signal in the cell decreases and the repression of the SOS genes is restored.
Insights
Escherichia coli activates the SOS response to repair DNA damage using over 20 genes. Activated RecA protein triggers LexA cleavage, initiating DNA repair and cell survival mechanisms.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Escherichia coli employs a complex adaptive mechanism, the SOS response, to survive DNA damage.
- Over 20 SOS genes are induced by DNA-damaging agents or inhibitors of DNA synthesis.
- These genes are regulated by the LexA repressor binding to conserved "SOS box" sequences.
Purpose of the Study:
- To elucidate the regulatory mechanism of the SOS response in Escherichia coli.
- To understand the role of RecA and LexA proteins in DNA damage adaptation.
Main Methods:
- The study focuses on the molecular interactions between RecA, LexA, and DNA.
- Analysis of gene regulation through DNA damage and repair pathways.
Main Results:
- DNA damage generates single-stranded DNA, which activates the RecA protein.
- Activated RecA promotes LexA autocleavage, releasing the SOS genes from repression.
- Induced SOS genes facilitate DNA repair via recombination, excision, and error-prone mechanisms.
Conclusions:
- The SOS response is a critical survival mechanism in E. coli involving RecA-mediated LexA cleavage.
- This intricate system allows cells to repair DNA lesions and restore normal gene expression.