Mechanism of Puromycin Action: Fate of Ribosomes after Release of Nascent Protein Chains from Polysomes

Abstract

The exchange of ribosomal subunits during the release of growing polypeptide chains by puromycin has been investigated in a bacterial cell-free system engaged in protein synthesis. The addition of sperinidine, used as a stabilizing agent of 70S monomers, caused a strong inhibition of the subunit exchange. This result led us to conclude that upon premature release of unfinished protein chains by the antibiotic, the ribosomes fall off mRNA as 70S particles. This behavior is different from that occurring during physiological termination of translation, where the ribosomes detach in a dissociated form. Some implications of the postulated mechanism are also discussed.Puromycin is a well-known inhibitor of protein synthesis in vivo as well as in cell-free systems. Its structure, analogous to aminoacyl-tRNA, leads to the premature release of unfinished polypeptide chains as polypeptidyl-puromycin derivatives (1-4).However, the fate of ribosomes upon release of growing protein chains by puromycin is still not well understood. Schlessinger et al. (5) reported that ribosomes engaged in polyphenylalanine synthesis were dissociated into subunits after treatment with puromycin, because the free 30S-50S couples were unstable. More recently Kohler et al. (6) could not confirm these results; they found that 708 particles bearing polyphenylalanyl-tRNA remained intact when peptide chains were liberated by the antibiotic.Both experiments lead to opposite conclusions, but neither of them can be used as a good model of the puromycin reaction at the polysomal level, which constitutes a more physiological system.

Induction of fetal hemoglobin through enhanced translation efficiency of γ-globin mRNA

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Yeast Upf1 CH domain interacts with Rps26 of the 40S ribosomal subunit

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