Structural organization of a src gene from Xenopus laevis.

By sequence analysis of genomic clones, the exon-intron structure of one of the two src genes from Xenopus laevis has been determined. The coding region of the gene is interrupted by 10 introns whose locations are identical to the introns in the coding regions of the src genes of human and chicken. The 5' untranslated region is contained on a separate exon with no sequence conservation relative to the corresponding region of the chicken gene. The 5' untranslated region of the Xenopus gene contains a G + C-rich stem-loop sequence and two ATG triplets. A 1.4-kb fragment containing the 5' untranslated region and sequences upstream of it acts as a promoter when introduced in the correct orientation into X. laevis cell lines. The DNA sequence of this fragment lacks the typical arrangement of TATA and CCAAT sequences but contains the ATGCAAAT octamer sequence and a (TA)39 sequence.