Enhancer identification in K562 cells using the DLR assay with minP. (A) The constructs used in the reporter assay system are depicted. The pGL4.23 vector containing one minP was set as a negative control. The pGL4.23 construct with enhancer HS2 was set as a positive control. pGL4.23 constructs with DHSs of interest in the place of HS2 were used to evaluate the enhancer activities of DHSs. (B) Enhancer activities evaluation of 23 erythroid-specific or putative erythroid-specific DHSs in K562 cells. Each construct was transfected in triplicate at a time and transfections were repeated at least twice. For each construct, the firefly luciferase activity was normalized to that of Renilla luciferase. The relative luciferase activity was shown in log2 scale, with that of minP set to 0. Standard deviations were shown as error bars above each column. DHSs with 5-fold or higher activities than that of minP were defined as enhancers.