DNA polymerase ? specializes in incorporating synthetic expanded-size (xDNA) nucleotides.

ABSTRACT: DNA polymerase ? (Pol?) is a unique A-family polymerase that is essential for alternative end-joining (alt-EJ) of double-strand breaks (DSBs) and performs translesion synthesis. Because Pol? is highly expressed in cancer cells, confers resistance to ionizing radiation and chemotherapy agents, and promotes the survival of homologous recombination (HR) deficient cells, it represents a promising new cancer drug target. As a result, identifying substrates that are selective for this enzyme is a priority. Here, we demonstrate that Pol? efficiently and selectively incorporates into DNA large benzo-expanded nucleotide analogs (dxAMP, dxGMP, dxTMP, dxAMP) which exhibit canonical base-pairing and enhanced base stacking. In contrast, functionally related Y-family translesion polymerases exhibit a severely reduced ability to incorporate dxNMPs, and all other human polymerases tested from the X, B and A families fail to incorporate them under the same conditions as Pol?. We further find that Pol? is inhibited after multiple dxGMP incorporation events, and that Pol? efficiency for dxGMP incorporation approaches that of native dGMP. These data demonstrate a unique function for Pol? in incorporating synthetic large-sized nucleotides and suggest the future possibility of the use of dxG nucleoside or related prodrug analogs as selective inhibitors of Pol? activity.

SUBMITTER: Kent T 

PROVIDER: S-EPMC5100566 | biostudies-literature | 2016 Nov

REPOSITORIES: biostudies-literature