Studies on N4-(2-deoxy-D-pentofuranosyl)-4,6-diamino-5-formamidopyrimidine (Fapy.dA) and N6-(2-deoxy-D-pentofuranosyl)-6-diamino-5-formamido-4-hydroxypyrimidine (Fapy.dG).
Exposure of DNA to oxidative stress produces a variety of DNA lesions including the formamidopyrimidines, which are derived from the purines. These lesions may play important roles in carcinogenesis. We achieved the first chemical syntheses of a monomeric form of Fapy-dA (1) and oligonucleotides containing this lesion or Fapy-dG at a defined site. Monomeric Fapy-dA readily epimerized at 25 degrees C in phosphate buffer (pH 7.5). The beta-anomer was favored by a ratio of 1.33:1.0, and equilibration was achieved in less than 7 h. Deglycosylation of Fapy-dA in the monomer follows first-order kinetics from 37 to 90 degrees C. The rate constants for deglycosylation of Fapy-dA in the monomeric and oligonucleotide substrates were measured at a common temperature (55 degrees C) and found to be the same within experimental error (t(1/2) = 20.5 h). Implementation of the activation parameters measured for the deglycosylation of 1 indicates that the half-life for deglycosylation of Fapy-dA at 37 degrees C is approximately 103 h. Analysis of the rate constant for deglycosylation of Fapy-dG in an oligonucleotide, revealed that this lesion is approximately 25 times more resistant to hydrolysis than Fapy-dA at 55 degrees C. These results indicate that Fapy-dA and Fapy-dG will be sufficiently long-lived in DNA so as to warrant investigation of their genotoxicity, and both anomers will be present during this time.
Greenberg
M M
MM
Department of Chemistry, Colorado State University, Fort Collins, Colorado 80523, USA. mgreenbe@lamar.colostate.edu
Hantosi
Z
Z
Wiederholt
C J
CJ
Rithner
C D
CD
D002021:Buffers; D002851:Chromatography, High Pressure Liquid; D004249:DNA Damage; D004277:DNA, Single-Stranded / Q000737:chemistry; D003839:Deoxyadenosines / Q000737:chemistry; D003849:Deoxyguanosine / Q000737:chemistry; D005559:Formamides / Q000138:chemical synthesis / Q000737:chemistry* / Q000633:toxicity; D005663:Furans / Q000138:chemical synthesis / Q000737:chemistry* / Q000633:toxicity; D006031:Glycosylation; D009153:Mutagens / Q000138:chemical synthesis / Q000737:chemistry / Q000633:toxicity; D019906:Nuclear Magnetic Resonance, Biomolecular; D009691:Nucleic Acid Denaturation; D009841:Oligonucleotides / Q000138:chemical synthesis; D010710:Phosphates; D011743:Pyrimidines / Q000138:chemical synthesis / Q000737:chemistry* / Q000633:toxicity; D013237:Stereoisomerism; D013379:Substrate Specificity
D002021:Buffers; D004277:DNA, Single-Stranded; D003839:Deoxyadenosines; D005559:Formamides; D005663:Furans; D009153:Mutagens; C435881:N6-(2-deoxy-erythro-pentofuranosyl)-2,6-diamino-4-hydroxy-5-formamidopyrimidine; D009841:Oligonucleotides; D010710:Phosphates; D011743:Pyrimidines; D003849:Deoxyguanosine