FIGURE 6.

Overexpression of SRC-3 reverses the inhibitory effects of SUG-1 on RARα degradation and RARα-mediated transcription. A, in COS-1 cells cotransfected with RARα and SUG-1 expression vectors and RA-treated for 1 h, overexpression of SRC-3 reverses the interaction of SUG-1 with RARα. Nuclear extracts were immunoprecipitated with RARα monoclonal antibodies and analyzed by immunoblotting. The upper panels correspond to aliquots of unprecipitated extracts. B and C, COS-1 cells were cotransfected with the RARα vector and the DR5-tk-LUC reporter construct, along with SUG-1 and/or FLAG-SRC-3 and RA-treated. Extracts were analyzed by immunoblotting (B) and for luciferase activity (C). The results are the mean ± S.D. of at least three independent experiments. D and E, the same as in B and C but with SRC-1 instead of FLAG-SRC-3.