Mechanism of translesion synthesis past an equine estrogen-DNA adduct by Y-family DNA Polymerases

4-Hydroxyequilenin (4-OHEN)-dC is a major, potentially mutagenic DNA adduct induced by equine estrogens used for hormone replacement therapy. To study the miscoding property of 4-OHEN-dC and the involvement of Y-family human DNA polymerases (Pols) eta, kappa and L in that process, we incorporated 4-OHEN-dC into oligodeoxynucleotides and used them as templates in primer extension reactions catalyzed by pol 11, K and L. P01 11 inserted dAMP opposite 4-OHEN-dC, accompanied by lesser amounts of dCMP and c1TMP incorporation and base deletion. Pol K promoted base deletions as well as direct incorporation of dAMP and dCMP. POI L worked in conjunction with pol kappa, but not with pol eta, at a replication fork stalled by the adduct, resulting in increased dTMP incorporation. Our results provide a direct evidence that Y-family DNA pols can switch with one another during synthesis past the lesion. No direct incorporation of dGMP, the correct base, was observed with Y-family enzymes. The miscoding potency of 4-OHENdC may be associated with the development of reproductive cancers observed in women receiving hormone replacement therapy. (c) 2007 Elsevier Ltd. All rights reserved.