(A) YUGASP cells expressing either IFI6 or non-specific (NS) shRNA were analyzed by RT-qPCR. Expression of each gene was calculated in IFI6 knockdown cells relative to NS shRNA-expressing cells. (B) FACS analysis of YUGASP cells expressing NS or IFI6 shRNA. The percentage of cells in S phase is shown in red. (C) YUGASP cells expressing NS or IFI6 shRNA were analyzed using a DNA fiber assay. Representative images of the DNA fibers are shown. (D) YUGASP cells expressing NS or IFI6 shRNA were analyzed using the DNA fiber assay. Percentages of ongoing (ON), newly fired (NF), and terminated (Tr) DNA forks are shown. (E) YUGASP, SKMEL-103, and M318 cells expressing NS or IFI6 shRNA were analyzed for SA-β-gal activity. Representative images of cells stained for SA-β-gal activity for the indicated melanoma cell lines expressing NS or IFI6 shRNA are shown. (F) Percentage of SA-β-gal-positive cells for the experiment shown in panel E for the indicated melanoma cell lines expressing NS or IFI6 shRNA is plotted. (G) YUGASP, SKMEL-103 and M318 cells expressing each shRNA were analyzed for H3K9Ac, γH2A.X, and H2A.X using immunoblot. ACTINB was used as a loading control. In all panels, data are presented as mean ± SEM, and *p<0.05, **p<0.005.