A ribosomal frameshift occurs between the codons for Ser-32 and Asp-33. An autoregulatory mechanism enables modulation of frameshifting according to the cellular concentration of polyamines
[PMID:17332016]: "Ribosomes synthesizing antizyme start in one ORF and at the codon 5' adjacent to its stop codon, shift +1 to a second and partially overlapping ORF which encodes most of the protein. The ribosomal frameshifting is a sensor and effector of an autoregulatory circuit which is conserved in animals, fungi and protists. Stimulatory signals encoded 5' and 3' of the shift site act to program the frameshifting"; built with 1bp gap in exon 2 to represent the frameshift event