Novel cis element for tissue-specific transcription of rat platelet-derived growth factor beta-receptor gene

Platelet-derived growth factor (PDGF) and its receptors are widely expresse d in several tissues in the stage of cellular growth and development. In ad ulthood, PDGF beta-receptor (PDGF beta R) is mainly detected in pathologica l conditions such as atherosclerotic lesions and injured vascular wall. The purpose of the present study was to elucidate the underlying mechanism of PDGF beta R gene expression under pathological conditions in vascular smoot h muscle cells (VSMC) and to identify the important cis elements responsibl e for tissue-specific gene transcription. Cel mobility shift assay and supe rshift assay indicated that the CCAAT motif located at -67 (C67) was mainly interacted with NF-YC, and this element drove the basal promoter activity of the gene as a putative promoter. On the other hand, another important se quence essential for the basal transcription was found at a 30-bp region (R 30) spanning -150 to -121. To test whether R30 actually regulates the tissu e-specific transcription of PDGF beta R gene, electromobility shift pattern was compared between VSMC and hepatoma cell line (HTC). We obtained the re sult that DNA-protein complex seen only in nuclear extracts from HTC suppre ssed the promoter activity in HTC in a tissue-specific manner. Furthermore, cis element decoy transfection experiments for C67 and R30 also revealed t hat both elements were functionally important in mRNA expression of PDGF be ta R in VSMC. From these results, we concluded that the basal activity of P DGF beta R gene expression was transactivated by the interaction or coordin ation of both C67 and R30, and the latter one mainly controlled the tissue- specific gene expression in VSMC.