SUG-1 interacts with SRC-3 and contributes to RA-induced degradation of
SRC-3. A, in MCF7 and HeLa cells, MG132 reverses the RA-induced
degradation of SRC-3 and RARα (16 h). B, COS-1 cells were
transfected with the FLAG-SRC-3 vector in the absence or presence of SUG-1 and
treated or not with RA (1 h). Nuclear extracts were immunoprecipitated with
FLAG antibodies and analyzed by immunoblotting. The two upper panels
correspond to aliquots (10%) of unprecipitated extracts. C, in MCF7
cells, SUG-1 interacts with SRC-3 in coimmunoprecipitation experiments
performed with SRC-3 antibodies. D, immobilized GST and GST-SUG-1
proteins were incubated with extracts from COS-1 cells overexpressing SRC-3.
Bound SRC-3 was analyzed by immunoblotting. Lane 1 corresponds to 5%
of the loaded material. E, MCF7 and HeLa cells were transfected with
control or SUG-1 SMARTpool siRNA (50 nm) and RA-treated for 16 h.
Knockdown of SUG-1 was analyzed by immunoblotting as well as the expression
and degradation of SRC-3 and RARα. *, a nonspecific band
recognized by the RARα antibodies.