Quantitative analysis of the efficiency and mutagenic spectra of abasic lesion bypass catalyzed by human Y-family DNA polymerases

Higher eukaryotes encode various Y-family DNA polymerases to perform global DNA lesion bypass. To provide complete mutation spectra for abasic lesion bypass, we employed short oligonucleotide sequencing assays to determine the sequences of abasic lesion bypass products synthesized by human Y-family DNA polymerases eta (hPol eta), iota (hPol iota) and kappa (hPol kappa). The fourth human Y-family DNA polymerase, Rev1, failed to generate full-length lesion bypass products after 3 h. The results indicate that hPol iota generates mutations with a frequency from 10 to 80% during each nucleotide incorporation event. In contrast, hPol eta is the least error prone, generating the fewest mutations in the vicinity of the abasic lesion and inserting dAMP with a frequency of 67% opposite the abasic site. While the error frequency of hPol kappa is intermediate to those of hPol eta and hPol iota, hPol kappa has the highest potential to create frameshift mutations opposite the abasic site. Moreover, the time (t(50)(bypass)) required to bypass 50% of the abasic lesions encountered by hPol eta, hPol iota and hPol kappa was 4.6, 112 and 1 823 s, respectively. These t(50)(bypass) values indicate that, among the enzymes, hPol eta has the highest abasic lesion bypass efficiency. Together, our data suggest that hPol eta is best suited to perform abasic lesion bypass in vivo.