Human DNA polymerase λ catalyzes lesion bypass across benzo[a]pyrene-derived DNA adduct during base excision repair

► We examine the repair of an AP site in the context of clusters with bulky lesions. ► AP site opposite the cis-isomeric BP-dG-adduct is repaired using Polλ. ► AP site in adjacent 3′ (+1) position is the most difficult to repair. ► In position +1, dCTP is preferably inserted substrate for Polλ.