Translesion Synthesis by Human DNA Polymerase η across Thymine Glycol Lesions

Abstract

The XP-V (xeroderma pigmentosum variant) gene product, human DNA polymerase η (pol η), catalyzes efficient and accurate translesion synthesis (TLS) past cis−syn thymine−thymine dimers (TT dimer). In addition, recent reports suggest that pol η is involved in TLS past various other types of lesion, including an oxidative DNA damage, 8-hydroxyguanine. Here, we compare the abilities of pol α and pol η to replicate across thymine glycol (Tg) using purified synthetic oligomers containing a 5R- or 5S-Tg. DNA synthesis by pol α was inhibited at both steps of insertion of a nucleotide opposite the lesion and extension from the resulting product, indicating that pol α can weakly contribute to TLS past Tg lesions. In contrast, pol η catalyzed insertion opposite the lesion as efficient as that opposite undamaged T, while extension was inhibited especially on the 5S-Tg template. Thus, pol η catalyzed relatively efficient TLS past 5R-Tg than 5S-Tg. To compare the TLS abilities of pol η for these lesions, we determined the kinetic parameters of pol η for catalyzing TLS past a TT dimer, an N-2-acetylaminofluorene-modified guanine, and an abasic site analogue. The possible mechanisms of pol η-catalyzed TLS are discussed on the basis of these results.