Cloning and Nucleotide Sequence of a cDNA Clone Specifying Full Coding Exons of N- ras Gene from Sprague-Dawley Rat

A N- ras cDNA clone has been isolated and sequenced by application of a trascript-polymerase chain reaction (PCR) method. The cDNA sequence with 584 base pairs was selectively amplified from nanogram quantities of total RNA from Sprague-Dawley rat, and then directly cloned to M13mpl8 and M13mpl9. Nucleotide sequencing has revealed that this cDNA clone has full coding exons encompassing initiation to termination codons of a N- ras gene which exhibits more than 90% sequence homology with N-rav proto-oncogenes of mouse and human. A deduced amino acid sequence of this rat cDNA exhibits only three and four amino acid differences when compared with the N- ras gene products of mouse and human. The amino acid differences have been found in positions 69, 168, and 175 of mouse N- ras and positions 69, 175, 184, and 188 of human N- ras. All of the substitution positions are located in hydrophilic domains which have been known as nonessential amino acids for biochemical properties of the mammalian N- ras gene products.