Mapping of a transcription element critical for expression of the fibroblast growth factor receptor 1 gene

The fibroblast growth factor receptor 1 (FGFR1) gene has no TATA or CCAAT-elements. To examine its mechanism of expression, we characterized the transcription element of this gene. The basal promoter element was mapped to the 5'-flanking region from -89 to -43. The DNase I protection assay and gel shift analysis revealed that a nuclear protein extracted from FGFR1-expressing cells (NIH3T3 and SC-3), but not from FGFR1-nonexpressing cells (P3U1), could bind to the nucleotide sequence from -62 to -42. The molecular weight of this protein was approximately 100 kDa by Southwestern analysis. In addition, both the promoter activity and the nuclear protein binding activity were markedly impaired by the substitution of two bases within this footprint site. Interestingly, this footprint site appeared to lack the consensus sequence of the currently reported transcription factors. These results indicate that the 5'-flanking region from -62 to -42 plays a pivotal role in FGFR1 gene expression.