Since characterization of the Hippo pathway as a major regulator of growth control and organ size, major efforts to unravel the molecular mechanisms that regulate this pathway have been undertaken. These investigations have led to the discovery of diverse upstream regulators of Hippo signaling, the majority of which function to activate the Hippo kinase cascade and thereby restrict the transcriptional output of the downstream targets, Yorkie (Yki) in flies and TAZ and YAP in mammals, collectively Yki/TAZ/YAP. Two studies have delineated a role for HIPK (homeodomain-interacting protein kinase) in promoting Yki/TAZ/YAP transcriptional activity.
