Molecular Biology

Translational Trickery and Polyamines

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Science  05 May 2000:
Vol. 288, Issue 5467, pp. 773
DOI: 10.1126/science.288.5467.773d

Polyamines are essential for the proliferation of eukaryotic cells. Their intracellular concentrations are regulated through the cell cycle and largely determined by the level of ornithine decarboxylase (ODC), the rate-limiting synthetic enzyme.

Pyronnet et al. show that mammalian ODC messenger RNA contains a cap-independent internal ribosome entry site that functions exclusively at the G2/M phase of the cell cycle, a time when most protein synthesis is inhibited, thereby ensuring production of the polyamines needed for mitosis.

Ivanov et al. investigate a polyamine-enhanced ribosomal frameshifting event that occurs during translation of the mRNA for antizyme 1, a protein that targets ODC for degradation. They show that this programmed frameshifting is conserved from fission yeast to mammals, suggesting that it plays a fundamental role in cell physiology. In a separate study in mice, Ivanov et al. find a new antizyme paralog that is selectively expressed in testis germ cells, suggesting an involvement of this regulatory system in spermatogenesis.—PAK

Mol. Cell5, 607 (2000); EMBO J.19, 1907 (2000); Proc. Natl. Acad. Sci. U.S.A.97, 4808 (2000).

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