YY1 and neoplasm: Mechanistically, NO donors such as S-nitroso-N-acetylpenicillamine (SNAP) and DETA-NONOate can S-nitrosylate the transcriptional repressor YY1, impairing its ability to bind the Fas promoter silencer region, thereby enhancing Fas expression and sensitizing tumor cells to FasL-induced apoptosis [110].