The Plt6 mutation reduces p300 affinity for c-Myb. GST, GST-p300 KIX (Y630N), and GST-p300 KIX (wild type; 2 μg each) were used as baits for pull-down experiments with ³⁵S-labeled, in vitro–transcribed/translated c-Myb. Pull-down reactions were resolved by SDS-PAGE followed by detection of bound ³⁵S-c-Myb by autoradiography. (A) Typical autoradiogram. (B) Coomassie blue staining to determine bait levels. (C) The amount of bound ³⁵S-c-Myb was determined by densitometric analysis of the autoradiographs of 3 independent experiments, and the ³⁵S-c-Myb bound by GST and GST-p300 KIX (Y630N) is shown relative to the amount bound by GST-p300 KIX (wild type). Data represent the mean of 3 independent experiments with error bars corresponding to SD.