3,N⁴-Ethano-2'-deoxycytidine: Chemistry of incorporation into oligomeric DNA and reassessment of miscoding potential

3,N⁴-Ethano-2'-deoxycytidine (ethano-dC) may be incorporated successfully into synthetic oligodeoxy-nucleotides by omitting the capping procedure used in the automated DNA synthetic protocols immediately after inserting the lesion and in all iterations thereafter. Ethano-dC is sensitive to acetic anhydride found in the capping reagent, and multiple oligomeric products are formed. These products were identified by examining the reaction of ethano-dC with the capping reagent, and several acetylated, ring-opened products were characterized by electrospray mass spectrometry and collision induced dissociation experiments on a tandem quadrupole mass spectrometer. A scheme for the formation of the acetylated products is proposed. In addition, the mutagenic profile of ethano-dC was re-examined and compared to that for etheno-dC. Ethano-dC is principally a blocking lesion; however, when encountered by the exo^- Klenow fragment of DNA polymerase, dAMP (22%), TMP (16%), dGMP (5.3%) and dCMP (1.2%) were all incorporated opposite ethano-dC, along with an oligomer containing a one-base deletion (0.6%).