Organization of the fibronectin gene provides evidence for exon shuffling during evolution

We report the organization of the two ends of the rat fibronectin gene which encode the type I and II repeating units of the protein. We show that each of these modular structural units is encoded by a separate exon. Homologous type I and II repeats are known to occur in tissue plasminogen activator, factor XII and a bovine seminal plasma protein. Comparison of these sequences and the exon structures of the fibronectin and tissue plasminogen activator genes indicates that exons encoding type I and type II repeats have reassorted during evolution. We also report analyses of the extreme 5' and 3' ends of the fibronectin gene including the promoter region and the exon encoding the prepro sequence of fibronectin and we show that the gene is transcribed from a single initiation site to a single polyadenylation site. These data provide information pertinent to the transcriptional regulation of the gene, the alternative splicing of the primary transcript and the structure of the primary translation product.