Promoter region of the murine fibroblast growth factor receptor 2 (bek/KGFR) gene.

Fibroblast growth factors (FGFs) and their receptors play an important role in cell growth, angiogenesis and embryonal development. Four distinct genes encoding fibroblast growth factor receptors (FGFRs) were identified: flg, encoding FGFR1, bek encoding FGFR2, and the genes for FGFR3 and FGFR4. Both FGFR2 and keratinocyte growth factor receptor (KGFR) are encoded by the same gene, bek. To study the regulation of expression of the FGF receptors we analysed the DNA sequence flanking the 5' region of the cDNA of murine FGFR2 to seek elements that control its transcription. A 5-kbp fragment containing the 5' end of the cDNA was isolated from mouse genomic library and used to map the promoter region. We found that the sequence encoding the 5' non-translated region of the FGFR2/KGFR cDNA contains an intron located 210 bp upstream from the translation start site. Using RNAase protection and primer extension, we identified the mRNA start 37 bp upstream from the beginning of the bek cDNA. The promoter activity was found to reside in a 1.3-kbp fragment upstream from the cDNA, and deletion mapping further localized the promoter to a 0.7-kbp fragment. The sequence of this region shows high G+C content (62%), which is particularly emphasized in the 200 bp upstream from the mRNA start (80% G+C). This region contains the CCGCCC, GGGCGG AND GGAGG motifs also found in promoters of other growth factor receptors. Neither TATA nor CAAT boxes were found near the RNA start site. The characterization of this promoter will allow studies of the regulation of expression of the FGFR2 during development and in pathophysiological states. The differences between the promoter sequence of the gene for FGFR2 (bek) and FGFR1 (flg) may explain their differential expression during development.