p53 enhances the interaction between HDMX and HDM2 in cells. (A) Controls of the proximity ligase assay (PLA) experiments. Panel A shows nontransfected cells H1299 that were analyzed for the HDMX‐HDM2 interaction. Dots representing the interaction of the endogens proteins can be appreciated. A double knockout H1299 HDM2/HDMX (H1299DKO) cells was done in order to observe the interaction of the transfected constructs avoiding the interferences of the endogenous proteins. Panel B shows PLA of the interaction of the HDMX‐HDM2 using nontransfected double knockout cells H1299DKO. Panel C shows transfected cells H1299DKO with HDMX and HDM2, the PLA was made using just one primary antiHDMX 5.1 antibody as a control. (B) The PLA for the HDMX and HDM2 interaction in the presence or absence of p53. H1299DKO cells were transfected with HDMX and HDM2 (upper panel) or with HDMX, HDM2 and p53 (lower panel). Anti‐HDM2 rabbit and anti‐HDMX mouse 5.1 were used. For IF of p53 anti‐p53 chicken antibody was used. Cell nuclei is visualized in blue with DAPI, p53 in green and the interaction in red. At least 30 cells were analyzed for each experiment. The quantification of the interaction was done with Image J software (*P < 0.05, **P < 0.01, ***P < 0.001).