Two divergent cellular src genes are expressed in Xenopus laevis.

Genomic and cDNA clones of the X. laevis src gene have been isolated and characterized by hybridization and DNA sequence analyses. The haploid genome of X. laevis contains two src genes, which can be distinguished from one another by virtue of sequence divergence in the 3' untranslated regions. Both of the genes are functional as indicated by the fact that oocytes contain RNAs transcribed from each of the genes. The two genes each encode an RNA which is 3.3 kb in length, or twice the length required to encode the 60,000 dalton src protein (pp60). Sequence analysis of the cDNA clones revealed that nearly all of the non-coding sequence is located at the 3' end. The availability of sequence data from cDNA clones has also made it possible for the first time to identify with certainty the carboxyl terminal sequence of a cellular pp60 molecule.