Chicken proto-oncogene c-ros cDNA clones: identification of a c-ros RNA transcript and deduction of the amino acid sequence of the carboxyl terminus of the c-ros product.

Three overlapping cDNA clones that hybridized to a v-ros probe were isolated from a cDNA library constructed from chicken kidney mRNA. Sequence analysis of these clones showed that they were all derived from c-ros mRNA. Using hybridization probes synthesized from the cDNA clones, a c-ros mRNA transcript of approximately 8.3 kb was detected in chicken kidney RNA, but not in chick embryo fibroblast RNA. The amino acid sequence predicted from the cDNA sequence indicates that the carboxyl terminus of the chicken c-ros protein contains 58 amino acids which are not present in v-ros. The predicted amino acid sequence of the chicken c-ros protein differs by 25% from that of its closest known human counterparts within the tyrosine protein kinase catalytic domain, and by 66% downstream of this domain. Despite these differences, both the chicken and human amino acid sequences share a potential site of tyrosine phosphorylation near their carboxyl termini that is absent from v-ros.