K-ras oncogene expression in Xenopus laevis.

A Xenopus laevis homolog of mammalian Kirsten-ras has been isolated from an oocyte cDNA library. This ras clone has been used to examine the genomic representation and expression of ras in oocytes and embryos. The Xenopus homolog of K-ras is a low-copy gene encoding a 2.6 kb mRNA, which is present throughout oogenesis and embryonic development. DNA sequence analysis indicates that Xenopus and mammalian K-ras 2B are highly conserved at the mRNA level (82%) and encode nearly identical proteins. It should now be feasible to address the function of endogenous ras oncogene in the well-characterized Xenopus developmental system.