Megakaryocyte-specific promoter activity is dependent on the distal NFAT site. Untreated and 4-day PMA-differentiated CMK cells were transfected with the reporter constructs containing mutations to the putative transcription factor binding sites shown (represented by the schematics). Twenty-four hours after transfection, luciferase activity was assessed and expressed as percent of activity relative to the −391-bp wild-type construct. The bars represent means plus or minus the standard error from 3 independent experiments.