A WW domain‐containing Yes‐associated protein (YAP) is a novel transcriptional co‐activator

A protein module called the WW domain recognizes and binds to a short oligopeptide called the PY motif, PPxY, to mediate protein–protein interactions. The PY motif is present in the transcription activation domains of a wide range of transcription factors including c‐Jun, AP‐2, NF‐E2, C/EBPα and PEBP2/CBF, suggesting that it plays an important role in transcriptional activation. We show here that mutation of the PY motif in the subregion of the activation domain of the DNA‐binding subunit of PEBP2, PEBP2α, abolishes its transactivation function. Using yeast two‐hybrid screening, we demonstrate that Yes‐associated protein (YAP) binds to the PY motif of PEBP2α through its WW domain. The C‐terminal region of YAP fused to the DNA‐binding domain of GAL4 showed transactivation as strong as that of GAL4–VP16. Exogenously expressed YAP conferred transcription‐stimulating activity on the PY motif fused to the GAL4 DNA‐binding domain as well as to native PEBP2α. The osteocalcin promoter was stimulated by exogenous PEBP2αA and a dominant negative form of YAP strongly inhibited this activity, suggesting YAP involvement in this promoter activity in vivo. These results indicate that the PY motif is a novel transcription activation domain that functions by recruiting YAP as a strong transcription activator to target genes.