and observed clear dose-dependent ubiquitination of BRD4, but not CBP, with all four Degraders tested (Figure ). A hook effect was evident for BRD4 ubiquitination, with structure activity relationship (SAR) suggesting a greater degree of ubiquitination at lower compound concentration with increased linker length. FLAG-BRD4 and GST-CREBBP were detected using capillary electrophoresis (Simple Western, Wes) and anti-FLAG, anti-GST antibodies.