Figure 2. UVB promotes Z-DNA formation via oxidative DNA damage.

A. Representative confocal images of the mitochondrial outer membrane (TOMM20), Z-DNA and 8oxodG in N/TERTs at baseline, 3h after UVB exposure with or without IFNα preincubation for 16h. Scale bar 10μm. B. Magnified region from (A) highlighting proximity and colocalization of Z-DNA with intense 8oxodG staining in areas outside of mitochondria. C. Representative line scan from Z-DNA puncta in (B) highlighting the absence of TOMM20 in spots of Z-DNA accumulation. D. Correlation of the Z-DNA puncta per cell with matched average 8oxodG per cell. E. Change of A260/295 as a measure of B-DNA (high ratio~10) vs Z-DNA (lower ratio of ~3) formation is graphed comparing low salt vs. high salt conditions after 2h at 37ºC. F. Naked polydGdC was irradiated with indicated UVB doses and incubated in indicated [NaCl] as in E. to induce Z-DNA. No shift to a lower ratio in lower [NaCl] was detected after UVB light exposure. G. To test the effect of oxidation on propensity for Z-DNA formation, polydGdC was treated with H2O2 (1mM) for 2h at 37ºC and subjected to varying salt concentrations as in E. Buffers with indicated NaCl and H2O2 without DNA served as blanks for the assay.