8-(Hydroxymethyl)-3,N4-etheno-C, a potential carcinogenic glycidaldehyde product, miscodes in vitro using mammalian DNA polymerases

8-(Hydroxymethyl)-3,N-4-etheno-C (8-HM-is an element ofC) is an exocyclic adduct resulting from the reaction of dC with glycidaldehyde, a mutagen and animal carcinogen. This compound has now been synthesized and its phosphoramidite incorporated site-specifically into a defined 25-mer oligonucleotide. In this study, the mutagenic potential of this adduct in the 25-mer oligonucleotide was investigated in all in vitro primer-template extension assay using four mammalian DNA polymerases. The miscoding potentials were also compared to those of an analogous derivative, 3,N-4-etheno C (is an element ofC), in the same sequence. Both adducts primarily blocked replication by calf thymus DNA polymerase alpha at the modified base, while human polymerase beta catalyzed measurable replication synthesis through both adducts. Nucleotide insertion experiments showed that dA and dC were incorporated by pol beta opposite either adduct, which would result in a C --> T transition or C --> G transversion. Human polymerase eta, a product of the xeroderma pigmentosum variant (XP-V) gene, catalyzed the most efficient bypass of the two lesions with 25% and 32% for 8-HM-is an element ofC and is an element ofC bypassed after 15 min. Varying amounts of all four bases opposite the modified bases resulted with pol eta. Human polymerase kappa primarily blocked synthesis at the base prior to the adduct. However, some specific misincorporation of dT resulted, forming an is an element ofC.T or 8-HM-is an element ofC.T pair. From these data, we conclude that the newly synthesized glycidaldehyde-derived adduct, 8-HM-is an element ofC, is a miscoding lesion. The bypass efficiency and insertion specificity of 8-HM-is an element ofC and is an element ofC were similar for all four polymerases tested, which could be attributed to the similar planarity and sugar conformations for these two derivatives as demonstrated by molecular modeling studies.