CDK1 interacts with, and phosphorylates, EZH2 at Thr 487. (a) Lysates from 293T cells, transfected with plasmids encoding Myc–EZH2 and HA–CDK1 as indicated, were immunoprecipitated (IP) using anti-Myc and analysed by immunoblot using anti-Myc or anti-HA. IgG; immunoglobulin G. (b) Pulldowns. GST and GST–EZH2 were incubated with lysate from HeLa cells. Bound CDK1 was detected by immunoblotting. (c) Lysate from MCF7 cells was immunoprecipitated with antibodies against EZH2 (left) or CDK1 (right), and analysed by immunoblotting. (d) Cyclin B, CDK1 and GST–EZH2 were subjected to an in vitro kinase assay and analysed by mass spectrometry. The spectrum of the charged ion (m/z 724.7217) shows that Thr 487 is phosphorylated (lower case p) in the indicated peptide (top right). b ions, fragmentation ions containing the amino terminus of the peptide; y ions, fragmentation ions containing the carboxy terminus of the peptide. (e) In vitro kinase assay with CDK1, cyclin B, and wild-type GST–EZH2 (WT) or GST–EZH2T487A. Phosphorylation of EZH2 and H1 was visualized by autoradiography, and loading of GST–EZH2 and H1 was assessed by Coomassie-stained gel. (f) 293T cells were transfected with plasmids encoding wild-type Myc–EZH2 or Myc–EZH2T487A and treated with CDK1 inhibitor CGP74514A or DMSO. Lysates were immunoprecipitated with anti-Myc and analysed by immunoblotting. (g) MCF7 cells stably expressing wild-type Myc–EZH2 or Myc–EZH2T487A were transfected with control vector or plasmids encoding CDK1 and cyclin B, and infected with lentivirus expressing CDK1 shRNA, as indicated. Cells were labelled with [32P]-orthophosphate, EZH2 was immunoprecipitated from lysates with anti-Myc and analysed by autoradiography. Immunoblotting was used to confirm equal loading of EZH2 (bottom). (h) HeLa cells expressing Myc–EZH2 or Myc–EZH2T487A were transfected with plasmid encoding CDK1 and cyclin B, or control vector. Cell lysates were immunoprecipitated with anti-Myc and immunoblotted. (i) Lysates of HeLa cells transfected with plasmid encoding CDK1 and cyclin B, or control vector, were immunoprecipitated with anti-EZH2, and immunoblotted. (j) Immunoblot of lysates from HeLa cells treated with Nocodazole as indicated. Cell lysates were immunoprecipitated with anti-EZH2. (k) MCF7 cells stably expressing wild-type Myc–EZH2 were infected with lentivirus expressing control or CDK1 shRNA. Cell lysates were immunoprecipitated with anti-Myc and immunoblotted. Uncropped images of blots are shown in .