Expanding the repertoire of DNA polymerase substrates: template-instructed incorporation of non-nucleoside triphosphate analogues by DNA polymerases β and λ

We have recently shown that neither the base nor the sugar moieties of a nucleotide is an essential feature for its incorporation by DNA polymerases (pols) λ and β. Here we present the identification of novel non-nucleoside triphosphate (NNTP) derivatives belonging to three classes: (i) non-substrate-specific inhibitors of DNA pol λ; (ii) substrate inhibitors which could preferentially be incorporated by either DNA pol λ wild type or its Y505A mutant and (iii) the substrate inhibitor N-(Biphenylcarbonyl)-4-oxobutyl triphosphate which could be incorporated exclusively by DNA pol β in a Mg(2+)-dependent manner, and preferentially pairs with A on the template. This compound represents the first example of a substrate lacking both nucleobase and ribose residue, showing distinct base-pairing properties with normal bases. Therefore, this NNTP analog can be considered as the prototype of an entirely novel class of DNA pol substrates.