ESR1 and breast carcinoma: In previous studies examining the detailed biological functions of BIG3 in the E2-signalling of ERα-positive breast cancer cells5, 6, 7, 8, 9, we focused on the role of BIG3 as an in vitro PP1Cα interactor that contains a canonical PP1Cα–binding motif ‘RVxF’ sequence (1,228-KAVSF-1,232) (ref. 15), but not other PP1C-binding motifs such as G/SILK or MyPhoNe.