Tissue-specific expression of rat c-ros-1 gene and partial structural similarity of its predicted products with sev protein of Drosophila melanogaster.

The expression and predicted products of rat c-ros-1 gene, the proto-oncogene of v-ros in UR2 sarcoma virus, were characterized. The c-ros-1 gene was found to be expressed in a tissue-specific manner, and the sizes of its transcripts were heterogeneous: 8.2 kilobases (kb) long in lung and kidney tissues, 6.9 kb in heart tissue, and 2.4 kb and 1.9 kb in testis tissue. The c-ros-1 cDNAs were isolated from lung and heart tissues. The predicted product of the c-ros-1 gene in lung tissue was a receptor-type tyrosine kinase 2,317 amino acids long (including a very large extracellular domain of approximately 1,800 amino acids) which showed a partial but significant structural homology with the sev gene product of Drosophila melanogaster. An alternatively sliced lung transcript was found to encode a protein with external and transmembrane domains but not a tyrosine kinase catalytic domain. The predicted product in heart tissue was essentially identical to that in lung tissue except for a shorter amino-terminal region and a 21-amino-acid insertion in the extracellular domain. On the basis of these results, the c-ros-1 gene appears to be active in the lungs and kidneys and probably in the hearts of rats.