Mechanism of translesional synthesis repair in Caulobacter crescentus.

Abstract

DNA damage in cells results from variety of exogenous and endogenous factors. Under these circumstances, DNA repair is crucial for the maintenance of genomic integrity of cells. Translesional synthesis (TLS) is a type of error-prone repair mechanism found across all domains of life. In prokaryotes, TLS has been mostly studied in the context of Escherichia coli, even though the components of this pathway are not conserved across all bacterial species. This study is aimed at understanding the regulation of error-prone polymerase ImuC, which is implicated in TLS in Caulobacter crescentus and pathogenic bacteria like Mycobacterium tuberculosis and Pseudomonas aeruginosa. Our experiments suggest that deletion of imuC results in sensitivity to only certain types of DNA damaging agents like mitomycin C and ultraviolet rays indicating the specificity of the polymerase. Our preliminary experiments using bacterial two-hybrid assay shows that ImuC-mediated TLS proteins interact with replisome components like DnaN (β-clamp) and DnaE (high-fidelity replicative polymerase). We also observe that some of TLS proteins interact with the recombinase RecA as well as other putative repair protein like MmcB. Interaction of RecA with multiple repair and replisome components suggest that RecA might have a central role in recruiting repair components to the site of a lesion and thereby mediate repair pathway choice.