VGLL2 and TEAD1 fusion proteins identified in human sarcoma drive YAP/TAZ-independent tumorigenesis by engaging EP300

Studies on Hippo pathway regulation of tumorigenesis largely center on YAP and TAZ, the transcriptional co-regulators of TEADs. Here, we present an oncogenic mechanism involving VGLL and TEAD fusions that is Hippo pathway-related but YAP/TAZ-independent. We characterize two recurrent fusions, VGLL2-NCOA2 and TEAD1-NCOA2, recently identified in human spindle cell rhabdomyosarcoma. We demonstrate that in contrast to VGLL2 and TEAD1 the fusion proteins are potent activators of TEAD-dependent transcription, and the function of these fusion proteins does not require YAP/TAZ. Furthermore, we identify that VGLL2 and TEAD1 fusions engage specific epigenetic regulation by recruiting histone acetyltransferase EP300 to control TEAD-mediated transcriptional and epigenetic landscapes. We show that small-molecule EP300 inhibition can suppress fusion protein-induced oncogenic transformation both in vitro and in vivo in mouse models. Overall, our study reveals a molecular basis for VGLL involvement in cancer and provides a framework for targeting tumors carrying VGLL, TEAD, or NCOA translocations.