WW-domain binding protein 2 (WBP2) is an adaptor protein first identified in a screen for proteins that interact with YAP1. WBP2 was subsequently shown to bind other WW domain-containing proteins, including TAZ and NEDD4-like ubiquitin-protein ligases. There is strong evidence for a conserved functional role for WBP2 in the Hippo kinase tumor suppressor pathway. WBP2 interaction is required for the oncogenic properties of TAZ in breast cancer cells and the growth-promoting properties of the YAP homolog Yorkie in Drosophila. In vitro studies have also suggested that WBP2 may act as a transcriptional co-activator of both estrogen and progesterone receptors; this interaction was shown to be dependent upon tyrosine phosphorylation of WBP2 by c-Src and c-Yes kinases.