FIG. 1.

(A and B) Endogenous MDM2 associates with endogenous E-cadherin. Exponentially growing MCF-7 cells were treated with 20 μM MG132, a proteasome inhibitor, for 4 h as indicated. The cell lysates were subjected to immunoprecipitation (IP) with antibodies against MDM2 (N-20) (A), E-cadherin (B), or control immunoglobulin G (IgG). The immunoprecipitates were separated by SDS-PAGE and subjected to IB with an anti-E-cadherin or an anti-MDM2 antibody for the detection of endogenous E-cadherin and MDM2, respectively. (C) MDM2 interacts with E-cadherin directly. In vitro-translated MDM2 was mixed with either purified GST or a GST-E-cadherin fusion protein in RIPA buffer. The reactions were pulled down with glutathione-agarose beads that were then boiled and separated by SDS-PAGE followed by IB with an anti-MDM2 antibody. As a control, 5% of the in vitro-translated MDM2 was loaded into the input lane.