Functional characterization of the human basic fibroblast growth factor gene promoter.

In order to understand the regulation of basic fibroblast growth factor (bFGF) gene expression, we have cloned and characterized the human bFGF gene and its regulatory elements. Using restriction endonuclease digestion, we have mapped the entire gene and sequenced all intron/exon boundaries to confirm authenticity and to determine organization. The data show that intron 1 is at least 16 kb long while intron 2 is 16 kb long. The human bFGF gene, including its three exons, is therefore at least 36 kb long. There are five GC boxes which may represent SP-1 binding sites and one potential AP-1 binding site within the core promoter region. Primer extension analysis indicates the presence of one bFGF-RNA transcription start site. We used a standard bacterial CAT gene expression system to identify the DNA sequence containing the functional bFGF gene promoter. Deletion analysis suggests the presence of two negative regulatory elements; one in the non-transcribed 5'-promoter region and the other within transcribed (but non-translated) sequences 3' of the promoter core.