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Abstract

Mutations of the ras proto-oncogenes rasH, rasK and rasN have been found in many human tumours and in the ras genes of the acutely transforming animal retroviruses HaMuSV and KiMuSV. (for reviews see Gibbs et al., 1985; Barbacid, 1987). These mutations were found to be single or double point mutations and could be localized in all cases to two different regions of the amino acid sequence of the ras encoded p21 proteins. Thus, either amino acids 12/13 or amino acids 59/61 were found to be mutated. The retroviral p21 proteins of the Kirsten and Harvey strain of MuSV contain a double mutation involving glycine12 and alanines59, where alanine59 is changed to threonine in both cases (Dhar et al., 1982; Tsuchida et al., 1982; Yasuda et al., 1984).