Figure 1

Glucocorticoid receptor (GR) binding to p53 and p73. A and B, Saos-2 cells (p53-null) were transfected overnight with 200 ng GR DNA and 100 ng DNA encoding either p53 or p73β. Where indicated, transfected cells were treated with dexamethasone (Dex, 100 nM) for 17 hrs and then incubated in the presence or absence of MG132 (30 μM) for an additional 6 hrs. GR, p53, and p73 levels were monitored by immunblotting. C, Saos-2 cells were transfected with DNAs encoding GR, HA-p53, or HA-p73β (1 μg each) as indicated. Transfected cells were either untreated (no tr), treated with dexamethasone (+Dex, 100 nM) for 24 hrs, treated with MG132 (30 μM) for 6 hrs, or treated with dexamethasone for 17 hrs followed by incubation in dexamethasone plus MG132 for an additional 6 hrs. Cell lysates were immunoprecipitated with GR polyclonal antibody, followed by immunoblotting with a HA monoclonal antibody. The position of HA-p53 (left) and HA-p73β (right) that co-immunoprecipitated with GR is indicated. The asterisk indicates detection of the antibody heavy chain used in the immunoprecipitation. Levels of GR, HA-p53, and HA-p73 in transfected cell lysates determined by immunoblotting without prior immunoprecipitation are shown in the lower panels.