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Fig. S20
(+)-JQ1 is a highly specific inhibitor, which displaces BET proteins from chromatin by competitively binding to the acetyl-lysine recognition pocket of BET bromodomains. (A) Treatment of zebrafish embryos with (+)-JQ1 disrupted the chromatin occupancy of hBRD3-GFP as demonstrated by the absence of GFP-positive mitotic chromosomes in these embryos (0/142 GFP-positive cells) compared to 9/141 GFP-positive cells in the DMSO control group. (B–C) To further quantify the chromatin occupancy of hBRD3-GFP during mitosis, we selected ≥15 mitotic cells, as shown by DAPI staining, and counted how many of these cells were GFP positive in the presence of (+)-JQ1 or DMSO (control). Whereas in (+)-JQ1 treated embryos none of the DAPI positive mitotic chromosomes were GFP positive, in DMSO treated embryos 11 cells were double DAPI/GFP positive. Asterisk depicts GFP in the cytoplasm and arrow shows mitotic chromosomes.