Here, we find that in collective BC migration, not functions independently of both Scar and SAGA to regulate the expression of two upstream components of the Hippo pathway, resulting in the loss of F-actin polarity, the mislocalization of polarity determinants, a change in the size and orientation of cellular protrusions, and the loss of polarized migration, identifying not as an important regulator of the transcriptional network underlying collective cell migration. This evidence concerns the gene RPS4X and breast cancer.