Fig. 6: Nuclear p85β recruits the deubiquitinase USP7 to stabilize EZH1/2, increasing H3K27 tri-methylation.

a Nuclear p85β interacts with USP7, EZH1, and EZH2. DLD1 PIK3CA E545K cells were lysed and immunoprecipitated (IP) with either an anti-p85β or an anti-USP7 antibody, then blotted with indicated antibodies. b Nuclear p85β interacts with USP7, EZH1, and EZH2 in PIK3CA E545K mutant cells, but not in PIK3CA H1047R mutant cells. c The interaction between USP7 and EZH1 or EZH2 is reduced in p85β knockout cells. The indicated cell lines were lysed, IPed with either EZH1 or EZH2, then blotted with indicated antibodies. d The interaction between USP7 and EZH1 or EZH2 is reduced in p85β knockout PIK3CA E545K mutant MB361 cells. MB361 cells were transfected with scrambled siRNA (NC) or two independent siRNA against p85β. Cell lysates were IPed with either EZH1 or EZH2, then blotted with indicated antibodies. e Knockdown of p85α does not impact the interaction between USP7 and EZH1 or EZH2. DLD1 PIK3CA E545K cells were transfected with scrambled siRNA (NC) or two independent siRNA against p85α. Cell lysates were IPed with either EZH1 or EZH2, then blotted with indicated antibodies. f–h Deubiquitinase USP7 protects EZH1 and EZH2 from ubiquitin-mediated degradation. Lysates of DLD1 parental cells and USP7 knockout cells were blotted with indicated antibodies (f). DLD1 parental cells and USP7 knockout cells were treated with either vehicle or MG132 for 6 h and then blotted with indicated antibodies (g). After being treated with MG132 for 6 h, DLD1 parental cells and USP7 knockout cells were lysed, IPed with an antibody against either EZH1 or EZH2, then blotted with indicated antibodies (h). Similar results were reproduced three times.