Expression and transforming activity of a variant of the heparin-binding fibroblast growth factor receptor (flg) gene resulting from splicing of the alpha exon at an alternate 3′-acceptor site

Splicing at an alternate 3′-acceptor site results in deletion of a CCCAG in the 5′-sequence of the exon coding for the NH₂-terminal immunoglobulin-like disulfide loop of the heparin-binding fibroblast growth factor receptor (flg) alpha isoform. The result is an in-frame stop codon 138 base pairs after the first flg consensus translational initiation site. The next more favorable site predicts the same two loop intracellular receptor isoform, gamma, which was predicted from two different human cDNAs that arise by alternate use of two exons at the same site. Although expressed in normal tissue, the gamma mRNA is increased in rat prostate tumors and confers ability of anchorage-dependent cells expressing non-secreted heparin-binding fibroblast growth factors to grow in soft agar.