Mechanistic insight into oxidized ribonucleotide (8‐oxo‐GTP) insertion by a DNA polymerase

Abstract

During each cell division, more than 1 million ribonucleotides are misinserted into the genome. A close examination of the ribo‐ and deoxyribo‐nucleotide pools reveals the presence of damaged and potentially mutagenic nucleobases. In particular, 8‐oxo‐7,8‐dihydro‐2′‐deoxyguanosine (8‐oxo‐dG) is well‐known as a prevalent and mutagenic oxidized nucleobase that contributes to carcinogenesis and several neurological diseases. However, the mutagenic properties of its ribonucleotide equivalent (r8‐oxo‐GTP) remain poorly understood. Furthermore, the biological relevance of r8‐oxoGTP is underscored by the attenuated ability of nucleotide pool sanitizing enzyme MTH1 to catabolize r8‐oxo‐GTP. Using model DNA polymerases, DNA polymerase beta and Bst DNA Polymerase I, we comprehensively characterized r8‐oxoGTP insertion opposite cytosine (non‐mutagenic) and adenine (mutagenic) using both kinetic and structural techniques. Our results show that the 2′‐OH, unique to the ribo‐ form of 8‐oxo‐GTP, heavily diminishes the rate of insertion for r8‐oxo‐GTP opposite adenine and nearly eliminates its insertion opposite cytosine. These results provide novel insight into the mechanistic strategies employed by DNA polymerases to minimize the insertion of damaged ribonucleotides into the genome.Support or Funding InformationThis work was supported by the National Institutes of Health (grant number R01‐ES027558).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.