Role of p53 in sensing oxidative DNA damage in response to reactive oxygen species-generating agents.

The tumor suppressor p53 plays an important role in the regulation of cellular response to DNA damage. Recent studies suggest that p53 is able to bind DNA with certain structural alterations in a sequence-independent manner and to interact with several molecules involved in DNA repair. This study was undertaken to test the hypothesis that p53 may participate in sensing oxidative DNA damage, the most frequently occurring spontaneous DNA lesion, and modulate its repair by the base excision repair (BER) machinery. Using synthetic DNA containing 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxoG), we showed that p53 was pulled down together with two BER proteins, human 8-oxoguanine glycosylase (hOGG1) and AP endonuclease (APE). Functional analysis showed that p53 significantly enhanced the sequential activities of hOGG1 and APE in excising the 8-oxoG nucleotide from DNA in vitro. The ability of p53 to enhance the removal of oxidized DNA bases was further demonstrated in vivo using a pair of p53 isogenic lines. HCT116 p53+/+ cells exhibit a more rapid removal of 8-oxoG from DNA than p53-/- cells exposed to the same levels of reactive oxygen species (ROS) stress. Together, these results suggest that p53 participates in sensing oxidative DNA damage and modulates BER function in response to persistent ROS stress.