If the dialogue pertaining to globalization is to be directed or biased in any direction, then it must be this: that we consider the poor first. The 'polysemous' codon--a codon with multiple amino acid assignment caused by dual specificity of tRNA identity. In some Candida species, the universal CUG leucine codon is translated as serine. However, in most cases, the serine tRNAs responsible for this non-universal decoding (tRNA(Ser)CAG) accept in vitro not only serine, but also, to some extent, leucine. Nucleotide replacement experiments indicated that m1G37 is critical for leucylation activity. This finding was supported by the fact that the tRNA(Ser)CAGs possessing the leucylation activity always have m1G37, whereas that of Candida cylindracea, which possesses no leucylation activity, has A37. Quantification of defined aminoacetylated tRNAs in cells demonstrated that 3% of the tRNA(Ser)CAGs possessing m1G37 were, in fact, charged with leucine in vivo. A genetic approach using an auxotroph mutant of C.maltosa possessing this type of tRNA(Ser)CAG also suggested that the URA3 gene inactivated due to the translation of CUG as serine was rescued by a slight incorporation of leucine into the polypeptide, which demonstrated that the tRNA charged with multiple amino acids could participate in the translation. These findings provide the first evidence that two distinct amino acids are assigned by a single codon, which occurs naturally in the translation process of certain Candida species. We term this novel type of codon a 'polysemous codon'. (termed tRNA Ser CAG), and revealed its decoding mechan-Bioscience and Biotechnology, Tokyo Institute of Technology, ism by means of an in vitro translational assay system Nagatsuta, Midori-ku, Yokohama 227, Japan (Yokogawa et al., 1992; Suzuki et al., 1994) . Furthermore, 2 Corresponding authors when we investigated the distribution of this non-universal genetic code in fungi, as well as C.cylindracea, eight other In some Candida species, the universal CUG leucine