Date of Award
DNA repair, Escherichia coli, DNA polymerases, Crosslinking (Polymerization)
The chemical compounds 8-methoxy-psoralen and angelicin are two types of furocoumarins that intercalate into DNA and form mono-adducts when exposed to UVA light. However, 8-methoxy-psoralen, is also capable of forming a DNA interstrand cross-link in addition to mono-adducts. These lesions change the structure of DNA and block the DNA polymerase during replication, leading to lethality, mutagenesis, or rearrangements if not repaired. The repair of monoadducts is known to be carried out by nucleotide excision repair. However, how interstrand DNA crosslinks are repaired is less clear. The repair of crosslinks has been proposed to involve a number of pathways, which include: homologous recombination, base excision repair, nucleotide excision repair, and translesion synthesis. The purpose of this study is to determine whether a bacterial strain lacking all three translesion DNA polymerases is hypersensitive to these photosensitizing chemicals, and whether it is specifically hypersensitive to DNA interstrand crosslinks. Wild type, polB-dinB-umuDC (lacking the three polymerases), and uvrA mutants were each treated with either 8-methoxy-psoralen or angelicin and irradiated with UVA light to determine their relative survivals. I found that the mutant lacking all three DNA polymerases was more sensitive to 8-methoxy-psoralen than angelicin when compared to the wild type cells; yet, the overall sensitivity of the mutant was far less than that of the uvrA mutant. These observations suggest that translesion synthesis plays a role in the repair of interstrand crosslinks and could be consistent with models suggesting that translesion synthesis operates to fill gaps left following the incision of the initial strand.
Livingstone, Dena, "The Role of Translesion DNA Polymerase(s) in the Survival of Escherichia Coli Exposed to UVA Light in the Presence of Psoralen and Angelicin" (2015). University Honors Theses. Paper 199.