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Updated: May 7, 2026
A Deep-sequencing-assisted, Spontaneous Suppressor Screen in the Fission Yeast Schizosaccharomyces pombe
Published on: March 7, 2019
Specificity in suppression of SOS expression by recA4162 and uvrD303
Shawn C Massoni1, Steven J Sandler
1Department of Microbiology, Morrill Science Center IV N203, University of Massachusetts at Amherst, Amherst, MA 01003, USA.
Abstract:
Detection and repair of DNA damage is essential in all organisms and depends on the ability of proteins recognizing and processing specific DNA substrates. In E. coli, the RecA protein forms a filament on single-stranded DNA (ssDNA) produced by DNA damage and induces the SOS response. Previous work has shown that one type of recA mutation (e.g., recA4162 (I298V)) and one type of uvrD mutation (e.g., uvrD303 (D403A, D404A)) can differentially decrease SOS expression depending on the type of inducing treatments (UV damage versus RecA mutants that constitutively express SOS). Here it is tested using other SOS inducing conditions if there is a general feature of ssDNA generated during these treatments that allows recA4162 and uvrD303 to decrease SOS expression. The SOS inducing conditions tested include growing cells containing temperature-sensitive DNA replication mutations (dnaE486, dnaG2903, dnaN159, dnaZ2016 (at 37°C)), a del(polA)501 mutation and induction of Double-Strand Breaks (DSBs). uvrD303 could decrease SOS expression under all conditions, while recA4162 could decrease SOS expression under all conditions except in the polA strain or when DSBs occur. It is hypothesized that recA4162 suppresses SOS expression best when the ssDNA occurs at a gap and that uvrD303 is able to decrease SOS expression when the ssDNA is either at a gap or when it is generated at a DSB (but does so better at a gap).
Insights
The RecA protein is crucial for DNA repair and the SOS response in E. coli. Specific mutations in RecA (recA4162) and UvrD (uvrD303) affect SOS expression differently depending on the DNA damage type, with UvrD mutations showing broader efficacy.
Area of Science:
- Molecular Biology
- Genetics
- DNA Repair Mechanisms
Background:
- DNA damage detection and repair are vital cellular processes.
- In E. coli, the RecA protein mediates the SOS response upon encountering single-stranded DNA (ssDNA) at sites of DNA damage.
- Specific mutations in recA and uvrD genes have been shown to modulate SOS expression.
Purpose of the Study:
- To investigate whether specific features of ssDNA generated under various SOS-inducing conditions influence the ability of recA4162 and uvrD303 mutations to decrease SOS expression.
- To determine if the observed effects of these mutations are general or specific to certain types of DNA damage.
Main Methods:
- Testing the effect of recA4162 and uvrD303 mutations on SOS expression under diverse SOS-inducing conditions.
- Inducing conditions included temperature-sensitive DNA replication mutations (dnaE486, dnaG2903, dnaN159, dnaZ2016), a del(polA)501 mutation, and induction of double-strand breaks (DSBs).
Main Results:
- The uvrD303 mutation decreased SOS expression under all tested conditions.
- The recA4162 mutation decreased SOS expression under most conditions, but failed to do so in the polA strain or when double-strand breaks were induced.
- These differential effects suggest a dependence on the nature and location of the ssDNA generated.
Conclusions:
- The uvrD303 mutation effectively reduces SOS expression regardless of the ssDNA generation mechanism (gap or DSB).
- The recA4162 mutation's suppression of SOS expression is most effective when ssDNA occurs at a DNA gap, indicating a preference for specific DNA structures.
- These findings highlight distinct roles for RecA and UvrD in modulating the SOS response based on the context of DNA damage.
