Cloning and characterization of a novel upstream untranslated exon of the mouse Fgf-1 gene

Cloning and characterization of a novel form of mouse fibroblast growth factor-1 (FGF-1) mRNA, FGF-1.G: differential expression of FGF-1 and FGF-1.G mRNAs during embryonic development and in postnatal tissues

The fibroblast growth factor-1 (FGF-1) gene is characterized by the presence of different untranslated exons in its 5' end that direct the expression of alternatively spliced mRNA variants (1.A, 1.B and 1.C) that encode for FGF-1. We have previously isolated a new mouse FGF-1 upstream untranslated exon, which we termed -1G. Here we report on the cloning and characterization of the FGF-1 mRNA isoform arising from -1G. This newly identified FGF-1 mRNA species (FGF-1.G), whose transcription start site maps 295 bp upstream from the splice donor site, is predominantly expressed in young liver and kidney, where it comprises 40.2% and 30.7%, respectively, of the total FGF-1 mRNA. While the FGF-1 mRNA comprising all of the FGF-1 transcripts was present in distinct tissues at embryonic days E12.5 and E15.5, the FGF-1.G mRNA was not detected during murine embryogenesis; therefore the role of FGF-1 in embryonic development must be attributed to FGF-1 mRNAs arising from upstream untranslated exons other than -1G. On the other hand, the parallel decrease of both FGF-1 and FGF-1.G mRNA levels we observed in the aging mouse kidney and liver suggests a role of FGF-1.G in normal cellular maintenance and survival.

Characterization of the entire transcription unit of the mouse fibroblast growth factor 1 (FGF-1) gene. Tissue-specific expression of the FGF-1.A mRNA

Fibroblast growth factor 1 (FGF-1, also known as acidic FGF) is a mitogen for a variety of mesoderm- and neuroectoderm-derived cells, as well as an angiogenic factor in vivo. It has been implicated in angiogenic diseases including atherosclerosis, cancer and inflammatory diseases. In the present study, the entire transcriptional unit of the mouse FGF-1 gene, including four promoters, is characterized. By nucleotide sequence and RNase protection analyses, we have determined that its 3'-end resides 3.2 kilobase pairs downstream from the stop codon. We have previously cloned and characterized the mouse homologue of the human 1B promoter, as well as a novel upstream untranslated exon. In order to elucidate the regulatory mechanism of FGF-1 gene expression, the mouse promoter containing TATA and CAAT consensus sequences (FGF-1. A) was isolated from a P1 library and characterized. We further determined that the mouse heart is the most abundant source for the FGF-1.A mRNA. Finally, via both RNase protection analysis and 5'-rapid amplification of cDNA ends, we determined the transcription start site of the FGF-1.A mRNA.