Oxidative stress at low levels can induce clustered DNA lesions leading to NHEJ mediated mutations

// Vyom Sharma 1 , Leonard B. Collins 1 , Ting-huei Chen 2 , Natalie Herr 1 , Shunichi Takeda 3 , Wei Sun 2 , James A. Swenberg 1 , Jun Nakamura 1 1 Department of Environmental Sciences and Engineering, Gillings School of Global Public Health, Chapel Hill, NC 27599, USA 2 Department of Genetics, The University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA 3 Department of Radiation Genetics, Graduate School of Medicine, Kyoto 606–8501, Japan Correspondence to: Jun Nakamura, email: [email protected] Keywords: oxidative stress, NHEJ, mutations, clustered DNA lesions, double strand breaks Received: October 04, 2015      Accepted: March 13, 2016      Published: March 23, 2016 ABSTRACT DNA damage and mutations induced by oxidative stress are associated with various different human pathologies including cancer. The facts that most human tumors are characterized by large genome rearrangements and glutathione depletion in mice results in deletions in DNA suggest that reactive oxygen species (ROS) may cause gene and chromosome mutations through DNA double strand breaks (DSBs). However, the generation of DSBs at low levels of ROS is still controversial. In the present study, we show that H 2 O 2 at biologically-relevant levels causes a marked increase in oxidative clustered DNA lesions (OCDLs) with a significant elevation of replication-independent DSBs. Although it is frequently reported that OCDLs are fingerprint of high-energy IR, our results indicate for the first time that H 2 O 2 , even at low levels, can also cause OCDLs leading to DSBs specifically in G1 cells. Furthermore, a reverse genetic approach revealed a significant contribution of the non-homologous end joining (NHEJ) pathway in H 2 O 2 -induced DNA repair & mutagenesis. This genomic instability induced by low levels of ROS may be involved in spontaneous mutagenesis and the etiology of a wide variety of human diseases like chronic inflammation-related disorders, carcinogenesis, neuro-degeneration and aging.