Effects of Stability of Base Pairs Containing an Oxazolone on DNA Elongation

Abstract EN

The nucleoside 2,2,4-triamino-5(2H)-oxazolone (Oz) can result from oxidative damage to guanine residues in DNA.

Despite differences among the three polymerases (Pol β, KF exo−, and Pol η) regarding nucleotide incorporation patterns opposite Oz, all three polymerases can incorporate guanine opposite Oz.

Based on ab initio calculations, we proposed a structure for a stable Oz:G base pair.

Here, to assess the stability of each Oz-containing base pair (Oz:G, Oz:A, Oz:C, and Oz:T) upon DNA replication, we determined the efficiency of Pol β-, KF exo−-, or Pol η-catalyzed primer extension beyond each base pair.

With each polymerase, extension beyond Oz:G was more efficient than that beyond Oz:A, Oz:C, or Oz:T.

Moreover, thermal denaturation studies revealed that the T m value for the duplex containing Oz:G was significantly higher than those obtained for duplexes containing Oz:A, Oz:C, or Oz:T.

Therefore, the results from ab initio calculations along with those from DNA replication assays and thermal denaturation experiments supported the conclusion that Oz:G is the most stable of the Oz-containing base pairs.