DNA synthesis past an abasic site, one of the most abundant DNA lesions, has been studied for several decades. Depending on the assay system and the type of cells, a 'C-rule', 'A-rule', or the lack of specificity have been reported. Yet, many questions on how a DNA polymerase interacts with and bypasses this lesion remain unanswered. In this study, we have evaluated replication of tetrahydrofuran (Z), a stable analog of abasic site, in several DNA polymerase knockout strains of Escherichia coli and in human embryonic kidney (HEK) 293T cells in 5'GZGTC and 5'GTGZC sequence contexts. The major mutations observed in both sequences were Z-to-T and targeted single-base deletions (Z-to-?). In the 5'GZGTC sequence, the major mutations in both SOS-induced and uninduced strains of E. coli were Z-to-? in pol IV- or pol V- deficient strain, whereas the major type of mutations for 5'GTGZC sequence changed depending on the SOS-induced or uninduced status and the E. coli strain. For the 5'GTGZC sequence with SOS in pol IV- deficient strain, Z-to-T occurred as the most common mutations while Z-to-? mutations dominated in the pol V- deficient strain, which suggests that pol IV and pol V may be involved in Z-to-? and Z-to-T, mutations, respectively. In contrast, the 'A-rule' was followed in HEK 293T cells, and 5'GZGTC and 5'GTGZC gave 80% and 87%, respectively, Z-to-T mutations. This indicates that sequence context and the type of cells may play significant roles in the mutagenic bypass of abasic sites.[Supported by NIEHS grant ES09127]

Effect of DNA sequence context in the translesion synthesis of an abasic site in <i>Escherichia coli</i> and human cells

247th National Meeting (2014)

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Effect of DNA sequence context in the translesion synthesis of an abasic site in Escherichia coli and human cells