Autoregulatory frameshifting in decoding mammalian ornithine decarboxylase antizyme

Abstract

Rat antizyme gene expression requires programmed, ribosomal frameshifting. A novel autoregulatory mechanism enables modulation of frameshifting according to the cellular concentration of polyamines. Antizyme binds to, and destabilizes, ornithine decarboxylase, a key enzyme in polyamine synthesis. Rapid degradation ensues, thus completing a regulatory circuit. In vitro experiments with a fusion construct using reticulocyte lysates demonstrate polyamine-dependent expression with a frameshift efficiency of 19% at the optimal concentration of spermidine. The frameshift is +1 and occurs at the codon just preceding the terminator of the initiating frame. Both the termination codon of the initiating frame and a pseudoknot downstream in the mRNA have a stimulatory effect. The shift site sequence, UCC-UGA-U, is not similar to other known frameshift sites. The mechanism does not seem to involve re-pairing of peptidyl-tRNA in the new frame but rather reading or occlusion of a fourth base.

Suppression of acetylpolyamine oxidase by selected AP-1 members regulates DNp73 abundance: mechanistic insights for overcoming DNp73-mediated resistance to chemotherapeutic drugs

“…The expression of Az is tightly controlled at the post-transcriptional level by a þ 1 frameshift translation mechanism, which is regulated by the polyamine biosynthesis pathway. 21 Polyamine homeostasis in cells is modulated by the interplay of several anabolic and catabolic enzymes 22 and we have now shown that paox is specifically targeted by selected AP-1 factors that were activated upon exposure to chemotherapeutic drugs. PAOX is a FAD-dependent oxidase that preferentially retro-converts NASp to spermidine and N-acetylspermidine to putrescine.…”

“…20 Az1 is a small inhibitory protein that binds to its target proteins and directs them to the proteasome for degradation. 21,22 Az1 transcript exists with two overlapping open reading frames, and translation of a fully functional Az1 protein requires a unique þ 1 ribosomal frameshift mechanism, which is dependent on the level of polyamines, a group of cationic compounds such as putrescine, spermidine and spermine present in the cells 21,22 ( Figure 1a, lower panel).…”

A code in the protein coding genes

“…Craigen and Caskey, 1986) and the rat ODCase antizyme gene (e.g. Matsufuji et al, 1995); and (iii) coding two proteins with a common N-terminal region and a different C-terminal region, e.g. the Escherichia coli dnaX gene (e.g.…”

“…If the spacing between the Shine-Dalgarno site and the frameshift trinucleotide is reduced to seven nucleotides then + 1 frameshift may occur (Larsen et al, 1994). Notes: the Shine-Dalgarno sites are observed six nucleotides upstream (−6) of the frameshift trinucleotides in the + 1 slipping process of prokaryotes (Weiss et al, 1988); a potential pseudoknot occurs five nucleotides downstream (+5) of the frameshift trinucleotide in the +1 slipping process of the ornithine decarboxylase antizyme gene of eukaryotes (Matsufuji et al, 1995). The window of X 0 could be involved in these different sequences of critical lengths (Larsen et al, 1994).…”

Skin fibroblasts from spermine synthase-deficient hemizygous gyro male (Gy/Y) mice overproduce spermidine and exhibit increased resistance to oxidative stress but decreased resistance to UV irradiation

“…In fact, the total polyamine content of the Gy\Y cells was almost 3-fold that of normal X\Y cells ( Figure 3D), whereas the total polyamine content of Gy\Y mouse tissues was not even twice that of normal mouse tissues [27]. There are several possible methods by which spermidine can down-regulate ODC, for example by interfering with ODC mRNA translation [12] or by inducing ribosomal frameshifting of the antizyme mRNA [35], leading to the synthesis of antizyme, which promotes the degradation of ODC by the 26 S proteasome [14]. In a previous study we demonstrated that spermidine depletion causes decreased transcription of the antizyme gene [32].…”