Involvement of specialized DNA polymerases in mutagenesis by 8-hydroxy-dGTP in human cells

The mutagenicity of an oxidized form of dGTP, 8-hydroxy-2'-deoxyguanosine 5'-triphosphate (8-OH-dGTP), was examined using human 293T cells. Shuttle plasmid DNA containing the supF gene was first transfected into the cells, and then 8-OH-dGTP was introduced by means of osmotic pressure. The DNAs replicated in the cells were recovered and then transfected into Escherichia coli. 8-OH-dGTP induced A:T-->C:G substitution mutations in the cells. The knock-downs of DNA polymerases eta and zeta, and REV1 by siRNAs reduced the A:T-->C:G substitution mutations, suggesting that these DNA polymerases are involved in the misincorporation of 8-OH-dGTP opposite A in human cells. In contrast, the knock-down of DNA polymerase iota did not affect the 8-OH-dGTP-induced mutations. The decrease in the induced mutation frequency was more evident by double knock-downs of DNA pols eta plus zeta and REV1 plus DNA pol zeta (but not by that of DNA pol eta plus REV1), suggesting that REV1-DNA pol eta and DNA pol zeta work in different steps. These results indicate that specialized DNA polymerases are involved in the mutagenesis induced by the oxidized dGTP.