FIG. 6.

Both ΦxxΦΦ and LxxLL core motifs participate in the CIA-ERα interaction. (A) Sequence alignment of p160 family member coactivator LxxLL and SMRT/N-CoR corepressor ΦxxΦΦ core motifs with the CIA BID. (B) Sequence of the CIA BID. Bold highlights indicate residues that have been mutated in CIAm1 (boxed LxxLL motif) and CIAm2 (boxed ΦxxΦΦ motif). (C) Ligand-dependent interaction between GST-CIA and ³⁵S-labeled ERα (lanes 3 to 6) is disrupted by mutation of the LxxLL motif in CIAm1. Basal and ligand-independent interactions between GST-CIA and ³⁵S-labeled ERα (lanes 7 and 8) are disrupted by mutation of the ΦxxΦΦ motif in CIAm2. (D) Coactivator function of CIA mutants assayed in vivo. Transfections were performed with COS-1 cells using the pS2-Luc reporter and pCMX-based expression vectors as described in Materials and Methods. Transfected cells were treated with either 10⁻⁸ M E₂ or the carrier (ethanol) for 24 h postinfection.