Development of a Plasmid-Based System for Studying DNA Repair Mechanisms in Escherichia coli

Nucleotide excision repair is a DNA repair mechanism involved in the repair of ultraviolet radiation damage. The key proteins in this system are the four Uvr proteins: UvrA, UvrB, UvrC, and UvrD. Previous studies have demonstrated that the nucleotide excision repair system is capable of repairing altered DNA structure, such as thymine dimers, in genomic DNA. Ultraviolet irradiated plasmid also generates thymine dimers, so we hypothesize that the nucleotide excision repair system can repair in vitro ultraviolet C damaged plasmids. This study aims to investigate the role of UvrB in the repair of in vitro ultraviolet C irradiated plasmid by using wild type and ΔuvrB Escherichia coli. Our results demonstrate that as the duration of plasmid irradiation increases, cell viability in both wild-type strain and ΔuvrB strain decreases. The ΔuvrB strain showed no difference in transformation frequency compared to wild-type strain, which suggests that the absence of UvrB in Escherichia coli does not cause additional deficiency in repairing ultraviolet C damaged plasmids. The result here suggests that there may be alternate deoxyribonucleic acid repair mechanisms that can repair ultraviolet damage or there may be other proteins that can compensate for the loss of UvrB.