SYNTHESIS AND TEMPLATE PROPERTIES OF AN ETHYL PHOSPHOTRIESTER MODIFIED DECADEOXYRIBONUCLEOTIDE

The phosphate groups of nucleic acids are often the targets of mutagenic and carcinogenic alkylating agents. To study the effects of alkyl phosphotriester modification on the physical and biochemical properties of DNA, 2 diastereomeric ethyl phosphotriester modified decadoexyribonucleotides, d-CpCpApApGp(Et)ApTpTpGpG isomer I and isomer II, were presented. A phosphotriester synthetic procedure was used to specifically place ethyl triester groups with an R or S configuration in the central dimer region of the decamer. Terminal deoxynucleotidyl transferase was used to add oligodeoxyadenylate tails to the 3'' end of the decamers. The resulting oligomers were tested as templates for Escherchia coli DNA polymerase I with d-(pT)8pCpC as a primer. The rates and extents of polymerization directed by the modified templates were 25% (isomer I) and 50% (isomer II) less than those of an unmodified control template. Thus, the presence of an ethyl triester group inhibits polymerization, the effectiveness of which is determined by orientation of the ethyl group relative to the rest of the template backbone. Evidently, ethyl phosphotriester lesions could inhibit replication rates of cellular DNA.