Cloning, sequencing, and embryonic expression of an N-ras proto-oncogene isolated from an enriched zebrafish (Danio...

An enriched zebrafish (Danio rerio) complementary DNA library was constructed for screening of ras-related genes, and a positive clone was isolated from one plate of 3 x 10(4) plaques. This clone, Zras-B1, carried an insert of 2592 base pairs (bp) with an open reading frame encoding a ras p21 protein of 188 amino acids. The deduced amino-terminal 86 amino acid residues and the carboxy-terminal CAAX binding motif are identical to mammalian ras. The full-length Zras-B1-encoded protein is most closely related to human N-ras (91% identity), with lesser homology to Ha-ras (84%) and Ki-ras (85%). Preliminary screening data also indicate other ras genes in zebrafish, at least one of which is also transcribed in adults. A Zras-B1-related 3.1-kb transcript was found to be abundant in embryos from zygote through gastrulation, and may be maternally derived.