Specificity of mutations induced by incorporation of oxidized dNTPs into DNA by human DNA polymerase η

Aberrant oxidation is a property of many tumor cells. Oxidation of DNA precursors, i.e., deoxynucleotide triphosphates (dNTPs), as well as DNA is a major cause of genome instability. Here, we report that human DNA polymerase eta (h Pol eta) incorporates oxidized dNTPs, i.e., 2-hydroxy-2'-deoxyadenosine 5'-triphosphate (2-OH-dATP) and 8-hydroxy-2'-deoxyguanosine 5'-triphosphate (8-OH-dGTP), into DNA in an erroneous and efficient manner, thereby inducing various types of mutations during in vitro gap-filling DNA synthesis. When 2-OH-dATP was present at a concentration equal to those of the four normal dNTPs in the reaction mixture, DNA synthesis by h Pol eta enhanced the frequency of G-to-T transversions eight-fold higher than that of the transversions in control where only the normal dNTPs were present. When 8-OH-dGTP was present at an equimolar concentration to the normal dNTPs, it enhanced the frequency of A-to-C transversions 17-fold higher than the control. It also increased the frequency of C-to-A transversions about two-fold. These results suggest that h Pol eta incorporates 2-OH-dATP opposite template G and incorporates 8-OH-dGTP opposite template A and slightly opposite template C during DNA synthesis. Besides base substitutions, h Pol eta enhanced the frequency of single-base frameshifts and deletions with the size of more than 100 base pairs when 8-OH-dGTP was present in the reaction mixture. Since h Pol eta is present in replication foci even without exogenous DNA damage, we suggest that h Pol eta may be involved in induction of various types of mutations through the erroneous and efficient incorporation of oxidized dNTPs into DNA in human cells. (c) 2007 Elsevier B.V. All rights reserved.