Interaction of ER, WT TRβ, and transactivation mutants with in vitro synthesized RIP140 and SRC-1. 35S-labeled in vitro translated RIP140 (a) and SRC-1 (b) were incubated with equal amounts of glutathione S-transferase (GST), GST-ER, or GST-TR fusion proteins in the presence (+) or absence (−) of 1 μM estradiol or T3, as appropriate.