Comparative analysis of RNA sequences from different organisms is informative about important features and the different options selected by evolution. Since most of the known examples of programmed frameshifting are in viruses or chromosomal mobile elements, the opportunity for comparison of frameshift cassettes in divergent organisms where the time of divergence can be approximated is limited. A start has been made with the frameshifting required for bacterial release factor 2 expression (Persson and Atkins, 1998) , but antizyme provides the ®rst opportunity for such a comparison in eukaryotes. Antizyme genes in genetically tractable lower eukaryotes would be helpful for understanding the functionally important interactions responsible for autoregulatory programmed frameshifting.