Identification of the Gene Regulatory Region in Human rasgrp2 Gene in Vascular Endothelial Cells

Ras guanyl nucleotide-releasing protein 2 (RASGRP2) is a calcium- and diacylglycerol-responsive guanine nucleotide exchange factor. Previously, we reported that XRASGRP2, a homolog of human RASGRP2, is expressed in the vascular region of the Xenopus embryo during embryogenesis. Here, we report the regulatory mechanisms of human rasgrp2 gene expression in vascular endothelial cells. Although three alternative splicing variants, differing in the first exon of 5'-untranslated region (5'-UTR), have been found for the human rasgrp2 gene, reverse transcription-polymerase chain reaction (RT-PCR) showed that the cDNA containing the distal first exon (DIE) was expressed only in human umbilical artery endothelial cells. We analyzed the 5'-flanking region of the human rasgrp2 gene by a luciferase assay, which revealed that not only a promoter but also silencer regions were present upstream of DIE, suggesting that rasgrp2 expression is controlled by a combination of transcriptional promotion and repression. Gel super shift assay demonstrated that OCT1/POU2F1 bound to the silencer region. These findings may help furthering our understanding of vasculogenesis and/or angiogenesis in vascular endothelial cells.