N2-Ethyl-2′-deoxyguanosine

N2-Et-dG, an adduct between DNA and the first metabolite of ethanol (acetaldehyde), strongly blocks transcription by RNA polymerases (RNAPs), including mammalian RNAPII and yeast RNAPII, E. coli RNAP, as well as T7 RNAP. All three of the multisubunit RNAPs incorporate a single rNTP residue opposite the N2-Et-dG lesion. The mammalian RNAPII exclusively incorporates cytidine monophosphate (CMP) opposite the N2-Et-dG lesion. The accessory transcription factor TFIIS does not usually act as a lesion bypass factor; instead, it stimulates the polymerase to remove the CMP incorporated opposite the lesion by mammalian RNAPII. N2-Et-dG reduces CTP incorporation by ~1500 fold.