Abstract
The recently identified Y-family DNA polymerases comprise proteins from different species including bacteria, eukarya and archaea. The most distinct feature of the polymerases is their ability to replicate DNA past damaged sites (translesion DNA synthesis). Some reactions they catalyze are error-free (correct bases are inserted opposite template lesions), while others are error-prone. Thus, the polymerases appear to play important roles in DNA damage tolerance and mutagenesis. However, damages are induced not only in DNA but also in its precursors, i.e., dNTP pool. Indeed, the incorporation of oxidized dNTPs into DNA is a major source of spontaneous mutagenesis and carcinogenesis. Here, we report that human DNA polymerase eta (pol η) incorporates oxidized dNTPs erroneously. The pol η preferentially incorporates 8-OH-dGTP opposite template A and incorporates 2-OH-dATP opposite template C, G or T. Pol η also efficiently elongates from primers having 8-OH-dG or 2-OH-dA as their 3'-termini. In addition, when the dinB gene encoding Pol IV and/or the umuDC genes encoding Pol V are disrupted in an sodAB fur strain of E. coli, the high spontaneous mutations were diminished by 80-90%. In the sodAB fur strain, superoxide stress and ion overload occur, which leads to high rates of spontaneous A:T to C:G and G:C-to-T:A mutations. The targets contributing to the mutator phenotypes are 8-OH-dGTP and 2-OH-dATP rather than DNA. Our results suggest that Y-family DNA polymerases may promote mutagenesis through the erroneous incorporation of oxidized dNTPs during DNA synthesis.
