Earlier studies suggest the importance of SUB1 in regulating transcription in vivo. For example, SUB1 enhances transcriptional activation by the activators GCN5 and HAP4 in yeast,43 and stimulates transcription in vitro with diverse kinds of activators, including SMYD3,32 VP16,24, 44 BRCA-145 and octomer transcription factor-1,46 possibly by facilitating assembly of the preinitiation complex. First, we compared motif occurrences within 500 bp upstream regions of downregulated genes and undifferentially expressed genes (when SUB1 is knocked down) using a computer program called CLOVER.47 Next, to validate the binding of SUB1 to PLK1, BUB1B and C-MYC promoters, we conducted chromatin immunoprecipitation (ChIP) assays using commercially available anti-SUB1 or -DDK antibodies in stable RWPE cells overexpressing lacz or Myc-DDK-tagged SUB1. As expected, SUB1 is enriched at PLK1, C-MYC and BUB1B promoter regions (Figures 5a–c). These data demonstrate that PLK1, C-MYC and BUB1B promoters are transcriptionally activated by SUB1 in prostate cancer.