Scheme of negative regulatory feedback in regulation of antizyme synthesis and conservation of the frameshift site. A. The competition between ribosomal frameshifting and standard translation (termination) is sensitive to polyamine levels. An increase in polyamine concentrations shifts the competition toward frameshifting resulting in elevation of antizyme synthesis and consequent inhibition of polyamine synthesis and uptake. A decrease in polyamine concentrations shifts the competition towards standard translation and produces the opposite effect on the synthesis of antizyme and polyamines. B. WebLogo representing the alignment of 153 OAZ sequences. The last codon in the zero frame and the first codon -in +1 frame are indicated by red and blue bars respectively. It can be seen that the only universal nucleotide of the frameshift site is T (U in mRNA) corresponding to the first position of the stop codon at the end of the first ORF.