To obtain information about the direct role played by PARP-1 in SNAI1 expression in MDA-MB-231 cells, ChIP assays were performed to analyse PARP-1 interactions with the promoter and the 3′ enhancer (Figure 3B), a region that is reported to control the expression of Snail in melanoma cells A375 [62]. Here, SNAI1 is linked to melanoma.