FIG. 6.

Mutation of LXXLL motifs in the context of the SRC1 minimal coactivator abrogates activity. A schematic diagram is shown representing full-length SRC1 (see the legend to Fig. 5A for details of the functional domains indicated by grey boxes) and the deletion constructs spanning the core coactivator domains and containing mutations in which the leucine doublet in two or more LXXLL motifs was mutated to alanines. Cos-1 cells were transfected as described in Materials and Methods with appropriate reporter constructs, vector expressing ER, and the SRC1 constructs as indicated. Luciferase activity was measured 24 h after the addition of 10⁻⁸ M E2, and the data were normalized to β-galactosidase activity. The activity of ER in the presence of ligand was set at 1, and the other values are expressed relative to it. The values shown represent the average of triplicate samples, and the error bars indicate standard deviation. The results shown are representative of experiments performed at least three times.