3,N-4-ethano-2 '-deoxycytidine: chemistry of incorporation into oligomericDNA and reassessment of miscoding potential

3,N-4-Ethano-2'-deoxycytidine (ethano-dC) may be incorporated successfully into synthetic oligodeoxynucleotides by omitting the capping procedure used in the automated DNA synthetic protocols immediately after inserting the l esion and in all iterations thereafter. Ethano-dC is sensitive to acetic an hydride 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 w ere characterized by electrospray mass spectrometry and collision induced d issociation 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 eth eno-dC. Ethano-dC is principally a blocking lesion; however, when encounter ed 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%).