The Hippo pathway regulates growth through the transcriptional coactivator Yorkie, but how Yorkie promotes transcription remains poorly understood. We address this by characterizing Yorkie@s association with chromatin and by identifying nuclear partners that effect transcriptional activation. Coimmunoprecipitation and mass spectrometry identify GAGA factor (GAF), the Brahma complex, and the Mediator complex as Yorkie-associated nuclear protein complexes. All three are required for Yorkie@s transcriptional activation of downstream genes, and GAF and the Brahma complex subunit Moira interact directly with Yorkie. Genome-wide chromatin-binding experiments identify thousands of Yorkie sites, most of which are associated with elevated transcription, based on genome-wide analysis of messenger RNA and histone H3K4Me3 modification. Chromatin binding also supports extensive functional overlap between Yorkie and GAF. Our studies suggest a widespread role for Yorkie as a regulator of transcription and identify recruitment of the chromatin-modifying GAF protein and BRM complex as a molecular mechanism for transcriptional activation by Yorkie.
Bibliographical noteFunding Information:
We thank B. Hay, C.P. Verrijzer, T. Xu, the DSHB, and the Bloomington Stock Center for antibodies and Drosophila stocks; and Flybase, Dibyendu Kumar, and the Waksman Genomics Core for bioinformatics and sequencing support. This research was supported by HHMI and by NIH grants GM078620 (to K.D.I.), 5R01GM054510 (to R.S.M.), 5P50GM081892 (to K.P.W.), and 3U01HG004264 (to K.P.W.).