Dissecting Hippo Interactions The Hippo signaling pathway plays key roles in many processes, from cell proliferation and cell death to regulation of stem cells and cancer cells. Kwon et al. (p. 737 , published 10 October) attempted to systematically identify all components of the pathway. A protein-protein interaction screen identified more than 200 interactions among approximately 150 proteins. A protein identified in the screen, Leash, restrained the activity of the transcriptional coactivator Yorkie, which regulates gene expression in response to Hippo signaling.