We further confirmed that the FLAG-tagged BIG3 mutant, which lacks an RVxF motif (ΔPP1Cα), completely abolished the interaction with endogenous PP1Cα (Supplementary Fig. 1b), indicating an in vivo endogenous BIG3–PP1Cα interaction in breast cancer cells. The gene discussed is ARFGEF3; the disease is breast carcinoma.