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Polyamines are required for entry and progression of the cell cycle. As such, augmentation of polyamine levels is essential for cellular transformation. Polyamines are autoregulated through induction of antizyme, which represses both the rate-limiting polyamine biosynthetic enzyme ornithine decarboxylase and cellular polyamine transport. In the present(More)
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(More)
Antizyme plays an important regulatory role in the synthesis of ornithine decarboxylase (ODC), a key enzyme of polyamine synthesis in higher animals. As well as inactivating polyamine uptake, antizyme is induced by polyamine-enhanced translational frameshifting, and binds to ODC, accelerating its ATP-dependent degradation, a process catalysed by the 26S(More)
Ornithine decarboxylase (ODC) is a key enzyme in polyamine biosynthesis. Turnover of ODC is extremely rapid and highly regulated, and is accelerated when polyamine levels increase. Polyamine-stimulated ODC degradation is mediated by association with antizyme (AZ), an ODC inhibitory protein induced by polyamines. ODC, in association with AZ, is degraded by(More)
Ornithine decarboxylase (ODC), a key enzyme in polyamine biosynthesis, is the most rapidly turned over mammalian enzyme. We have shown that its degradation is accelerated by ODC antizyme, an inhibitory protein induced by polyamines. This is a new type of enzyme regulation and may be a model for selective protein degradation. Here we report the(More)
Prion proteins are found in mammals and yeast, and can transmit diseases and encode heritable phenotypic traits. In Saccharomyces cerevisiae, eRF3, Rnq1, Ure2 and Swil are functional proteins with a soluble conformation that can switch to a non-functional, amyloid conformation denoted as [PSI+], [PIN+], [URE3] and [SWI+], respectively. The prion [PSI+](More)
The degradation of ornithine decarboxylase (ODC) is stimulated by polyamines in a protein synthesis-dependent manner. It has been suggested that antizyme, an ODC-inhibiting protein induced by polyamines, is involved in the process of polyamine-stimulated ODC decay. In this study, we investigated the direct effect of antizyme on ODC decay in hepatoma tissue(More)
Antizyme inhibitor was highly purified from rat liver by using affinity chromatography. It has some structural resemblance to ornithine decarboxylase (ODC), as judged from Mr, immunoreactivity and reversible binding with antizyme. However, unlike hepatic amounts of ODC and ODC-antizyme complex, that of antizyme inhibitor did not show much fluctuation upon(More)
Ornithine decarboxylase antizyme is a unique inhibitory protein induced by polyamines and involved in the regulation of ornithine decarboxylase. A cDNA was isolated from a rat liver cDNA library by the screening with monoclonal antibodies to rat liver antizyme as probes. The expression products of the cDNA in bacterial systems inhibited rat ornithine(More)
Antizyme inhibitor (AIn), a homolog of ODC, binds to antizyme and inactivates it. We report here that AIn increased at the G1 phase of the cell cycle, preceding the peak of ODC activity in HTC cells in culture. During interphase AIn was present mainly in the cytoplasm and turned over rapidly with the half-life of 10 to 20 min, while antizyme was localized(More)