YY1 and melanoma: siRNA knockdown of YY1 in the UACC903 melanoma cell line demonstrated a weak but consistent reduction of MX2 levels by four different sets of siRNAs (14–32% decrease, P = 1.5e−3–1.9e−5, one-sample Wilcoxon test; Fig. 5a; Supplementary Fig. 15a) indicating a regulation of MX2 levels by YY1.