PCAF-mediated acetylation of ISX recruits BRD4 to promote epithelial-mesenchymal transition

Epigenetic regulation is important for cancer progression; however, the underlying mechanisms, particularly those involving protein acetylation, remain to be fully understood. Here, we show that p300/CBP-associated factor (PCAF)-dependent acetylation of the transcription factor intestine-specific homeobox (ISX) regulates epithelial-mesenchymal transition (EMT) and promotes cancer metastasis. Mechanistically, PCAF acetylation of ISX at lysine 69 promotes the interaction with acetylated bromodomain-containing protein 4 (BRD4) at lysine 332 in tumor cells, and the translocation of the resulting complex into the nucleus. There, it binds to promoters of EMT genes, where acetylation of histone 3 at lysines 9, 14, and 18 initiates chromatin remodeling and subsequent transcriptional activation. Ectopic ISX expression enhances EMT marker expression, including TWIST1, Snail1, and VEGF, induces cancer metastasis, but suppresses E-cadherin expression. In lung cancer, ectopic expression of PCAF-ISX-BRD4 axis components correlates with clinical metastatic features and poor prognosis. These results suggest that the PCAF-ISX-BRD4 axis mediates EMT signaling and regulates tumor initiation and metastasis.