The GATA element at position −24 contributes to the transcriptional activity of the PECAM-1 promoter. HEL and Dami cells were transfected with the reporter constructs shown and cellular lysates assayed for luciferase activity to access transcriptional activity. Note that substitution of the sequence 5′-CTTT-3′ for the wild-type 5′-GATA-3′ resulted in a 70% reduction in PECAM-1 promoter activity in both megakaryocytic cell lines. PECAM-1-negative Raji cells showed no transcriptional activity when transfected with either reporter construct (data not shown). Data shown represent the mean ± SEM of three independent experiments, each performed in duplicate.