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Migration of 40 S ribosomal subunits on messenger RNA when initiation is perturbed by lowering magnesium or adding
Abstract:
Migration of 40 S ribosomal subunits on messenger RNA, detected previously in experiments using the antibiotic edeine (Kozak, M., and Shatkin, A.J. (1978) J. Biol. Chem. 253, 6568-6577) has now been observed in the presence of other inhibitors of initiation. 40 S subunit migration has been detected in both wheat germ and reticulocyte lysates treated with edeine, pactamycin, or sodium fluoride. The variety of structurally unrelated inhibitors that mediate this effect argues against the interpretation that migration is a drug-induced artifact. Indeed, limited migration of 40 S ribosomes occurs upon simply lowering the magnesium concentration, in the absence of inhibitors. Thus, migration seems to be an inherent property of 40 S ribosomal subunits and might be involved in the mechanism by which eukaryotic ribosomes select initiation sites in messenger RNA.
Insights
Eukaryotic 40 S ribosomal subunits migrate on messenger RNA, a process observed with various inhibitors and even without them. This inherent property may play a role in how ribosomes select mRNA initiation sites.
Area of Science:
- Molecular Biology
- Biochemistry
- Genetics
Background:
- Ribosome subunit migration on mRNA was previously observed with the antibiotic edeine.
- This phenomenon involves the movement of the 40 S ribosomal subunit along the messenger RNA molecule.
Purpose of the Study:
- To investigate the migration of 40 S ribosomal subunits on messenger RNA in the presence of various initiation inhibitors.
- To determine if this migration is an artifact of drug treatment or an inherent ribosomal property.
Main Methods:
- Experiments were conducted using wheat germ and reticulocyte lysates.
- Lysates were treated with inhibitors of initiation, including edeine, pactamycin, and sodium fluoride.
- Magnesium concentration was manipulated to observe its effect on ribosome migration.
Main Results:
- 40 S ribosomal subunit migration was observed with multiple structurally unrelated inhibitors (edeine, pactamycin, sodium fluoride).
- Limited migration also occurred upon lowering magnesium concentration, independent of inhibitors.
- These findings suggest migration is not solely a drug-induced artifact.
Conclusions:
- The migration of 40 S ribosomal subunits on mRNA appears to be an inherent property of these subunits.
- This inherent migration may be involved in the crucial process of eukaryotic ribosome initiation site selection on mRNA.