Phosphorylation of HOX11 Inhibits Transactivation of the Cyclin B1 ( CCNB1) Promoter. (A) Immunoblot of cyclin B1 levels following transfection of FLAG-tagged HOX11 wildtype and mutant cDNA. Vector alone (va), wildtype HOX11 (wt) and HOX11 Thr247Glu (T247E) are indicated. (B) Chromatin immunoprecipitation (ChIP) analysis using an anti-FLAG antibody on the CCNB1 promoter region following transfection of FLAG-tagged HOX11 wildtype and mutant cDNA. (C) Promoter-reporter assays for activation of the CCNB1 promoter containing or lacking the TAAGTG consensus site (CCNB1L-LUC, L ong and CCNB1S-LUC, S hort, respectively) following transfection of FLAG-tagged HOX11 wildtype and HOX11 T247A and HOX11 T247E mutant proteins. Each bar represents the fold ratio of luciferase activity between HOX11-deficient and HOX11-expressing cultures for each promoter-reporter construct. Each transfection was performed on three independent cultures. The results are representative of three independent experiments. Arbitrary luciferase units were standardized with Renilla.