Investigating the Importance of DinB‐RecA Interactions to the Regulation of DinB's Activity and the Fidelity of the DNA Damage Response

The error prone DNA Polymerase IV, DinB, specializes in synthesizing DNA from a lesion‐containing DNA template, an activity that allows cell survival during DNA‐damaging conditions at a mutagenic cost. We have shown that there is direct physical interaction between DinB and Escherichia coli's main recombinase, RecA. We also have i n vitro evidence suggesting that DinB•RecA interaction is conserved across many bacterial species, including human pathogens. Circular dichroism spectroscopy experiments show that the DinB•RecA complex undergoes a drastic conformational change compared to the single proteins alone. This is supported by the fact that DinB(C66A), a derivative with tight binding to RecA, and RecA copurify by size exclusion chromatography at a size that is much smaller than the size of the individual proteins, suggesting that compaction and tertiary structure changes are likely involved upon complex formation. Alteration of the physical interaction between DinB and RecA leads to changes in the mutagenic outcome in E. coli cells that are exposed to DNA damaging agents. Our current model is that the DinB•RecA complex not only alters the activity of DinB, but results in the sequestration of RecA from the lowest fidelity polymerase, DNA Polymerase V. The DinB•RecA complex, therefore, is central in controlling the fidelity of the DNA damage response. Source of Funding: R01 and its supplement from the National Institute of Health (NIH) Institute of General Medicine to V. Godoy