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. 2000 Apr 11;97(8):4363–4368. doi: 10.1073/pnas.97.8.4363

Figure 4.

Figure 4

Interaction between SRC-1–YFP and the CFP-tagged LBDs of RAR and ER. In vitro interaction of GST–SRC-1 and CFP–RAR LBD fusion proteins monitored by the GST pulldown assay in the presence or absence of the RAR agonist, TTNPB. (B) Dose-response of the interaction of CFP–RAR LBD and SRC-1–YFP in live cells monitored by FRET. (C) E2 promotes the interaction between GST–ER LBD and SRC-1–YFP in pulldown assays. (D) E2 stimulates FRET in a manner that is resistant to subsequent addition of tamoxifen (Tam). The figures on the right of the panel show the percentage of FRET efficiency calculated by using the YFP-photobleach protocol and indicate ligand-independent interaction in resting cells (16% in the absence of E2 and 23% in its presence). (E) FRET monitoring of CFP–ER LBD and SRC-1–YFP interaction. Tamoxifen inhibits basal FRET in a manner that is reversed by E2. The three channels (FRET, donor CFP, acceptor YFP) are shown. (F) ICI182,780 inhibits basal FRET between CFP–ER LBD and SRC-1–YFP in a manner that cannot be reversed by a 1,000-fold molar excess of E2.