HOX11 Binds to and Transcriptionally Modulates Expression of the Cyclin B1 ( CCNB1) Promoter. (A) Chromatin immunoprecipitation (ChIP) analysis using an anti-HOX11 antibody of six regions of the CCNB1 promoter region. (B) ChIP analysis of region 5 of the CCNB1 promoter using an anti-HOX11 antibody and an irrelevant antibody control. (C) Promoter-reporter assays to determine HOX11 transactivation of the empty reporter vector (pGL3), the CCNB1 promoter containing the TAAGTG consensus site (CCNB1L-LUC, L ong) and the CCNB1 promoter missing the TAAGTG consensus site (CCNB1S-LUC, S hort). Each bar represents the fold ratio of luciferase activity between HOX11- and vector alone-transfected cultures for each promoter-reporter construct. The results are representative of three independent experiments.