H2O2 signals via iron induction of VL30 retrotransposition correlated with cytotoxicity.

Abstract The impact of oxidative stress on mobilization of endogenous retroviruses and their effects on cell fate is unknown. We investigated the action of H 2 O 2 on retrotransposition of an EGFP-tagged mouse LTR-retrotransposon, VL30, in an NIH3T3 cell-retrotransposition assay. H 2 O 2 treatment of assay cells caused specific retrotranspositions documented by UV microscopy and PCR analysis. Flow cytometric analysis revealed an unusually high dose- and time-dependent retrotransposition frequency induced, ∼420,000-fold at 40 μM H 2 O 2 compared to the natural frequency, which was reduced by ectopic expression of catalase. Remarkably, H 2 O 2 moderately induced the RNA expression of retrotransposon B2 without affecting the basal expression of VL30s and L1 and significantly induced the expression of various endogenous reverse transcriptase genes. Further, whereas treatment with 50 μM FeCl 2 alone was ineffective, cotreatment with 10 μM H 2 O 2 and 50 μM FeCl 2 caused a 6-fold higher retrotransposition induction than H 2 O 2 alone, which was associated with cytotoxicity. H 2 O 2 - or H 2 O 2 /FeCl 2 -induced retrotransposition was significantly reduced by the iron chelator DFO or the antioxidant NAC, respectively. Furthermore, both H 2 O 2 -induced retrotransposition and associated cytotoxicity were inhibited after pretreatment of cells with DFO or the reverse transcriptase inhibitors efavirenz and etravirine. Our data show for the first time that H 2 O 2 , acting via iron, is a potent stimulus of retrotransposition contributing to oxidative stress-induced cell damage.