Identi®cation of an antizyme gene in Schizosaccharomyces pombe A search for DNA sequences encoding protein sequences homologous to Drosophila melanogaster antizyme (Ivanov et al., 1998b) and Homo sapiens antizyme 1 identi®ed the same S.pombe anonymous cDNA clone (DDBJ/EMBL/GenBank accession No. D89228). The similarity is limited (~10% identity, 24% similarity to both human antizyme 1 and D.melanogaster antizyme); however, it is highest in regions that are most highly conserved among the previously identi®ed antizymes ( Figure 1A ). Closer examination of the cDNA nucleotide sequence provided further evidence that it encodes an S.pombe homolog of antizyme. The initiating AUG codon for the ORF that is similar to higher eukaryotic antizymes (ORF2 of those genes) is not the 5¢-most AUG in this cDNA. In fact, there are eight AUGs closer to the 5¢ end. The ®rst or the second AUGs would initiate translation of an ORF (ORF1) that overlaps the longer downstream ORF (ORF2) such that a +1 translational frameshifting event in the overlap would generate a protein product analogous to the products of antizyme genes from higher eukaryotes. Furthermore, the last 12 nucleotides of ORF1 (UGG-UGC-UCC-UGA) are identical to the last 12 nucleotides of mammalian antizyme 1 ORF1s, including the frameshift site. Eleven of these 12 nucleotides are identical to the corresponding regions of all previously identi®ed antizyme genes ( Figure 1B ). Previous experiments with the mammalian frameshift sequence tested in S.pombe have shown that this short 12 nucleotide sequence, by itself, is suf®cient to stimulate measurable levels (up to 0.5%) of +1 frameshifting (Ivanov et al., 1998c) . To con®rm the ORF con®guration of the putative S.pombe antizyme gene, a region corresponding to the two overlapping ORFs plus~80 nucleotides of the 5¢ UTR and 370 nucleotides of the 3¢ UTR, was ampli®ed from both S.pombe genomic DNA and a cDNA library. The sequence of the ampli®ed DNA con®rmed that there are indeed two overlapping ORFs with the deduced con®guration. This sequence (DDBJ/EMBL/GenBank accession No. AF217277) differs from the previously sequenced cDNA clone by three nucleotides (two in the coding region and one in the 3¢ UTR); one changes an alanine codon to proline, another is a silent mutation within a proline codon. Since the sequences from the cDNA library and genomic DNA are identical, we conclude that the differences with clone No. D89228 are most likely due to strain variation. This gene contains no introns within the ampli®ed region.