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Translation reinitiation and development are compromised in similar ways by mutations in translation initiation factor eIF3h and the ribosomal protein RPL24.

Zhou F, Roy B, von Arnim AG - BMC Plant Biol. (2010)

Bottom Line: Like AtbZip11, the uORF-containing ARF mRNAs are indeed undertranslated in eif3h mutant seedlings.We conclude that, similar to eIF3h, RPL24B bolsters the reinitiation competence of uORF-translating ribosomes.Coordination between eIF3 and the large ribosomal subunit helps to fine-tune translation of uORF-containing mRNAs and, in turn, to orchestrate plant development.

View Article: PubMed Central - HTML - PubMed

Affiliation: Genome Science and Technology Program, The University of Tennessee, Knoxville, TN 37996, USA.

ABSTRACT

Background: Within the scanning model of translation initiation, reinitiation is a non-canonical mechanism that operates on mRNAs harboring upstream open reading frames. The h subunit of eukaryotic initiation factor 3 (eIF3) boosts translation reinitiation on the uORF-containing mRNA coding for the Arabidopsis bZip transcription factor, AtbZip11, among others. The RPL24B protein of the large ribosomal subunit, which is encoded by SHORT VALVE1, likewise fosters translation of uORF-containing mRNAs, for example mRNAs for auxin response transcription factors (ARFs).

Results: Here we tested the hypothesis that RPL24B and eIF3h affect translation reinitiation in a similar fashion. First, like eif3h mutants, rpl24b mutants under-translate the AtbZip11 mRNA, and the detailed spectrum of translational defects in rpl24b is remarkably similar to that of eif3h. Second, eif3h mutants display defects in auxin mediated organogenesis and gene expression, similar to rpl24b. Like AtbZip11, the uORF-containing ARF mRNAs are indeed undertranslated in eif3h mutant seedlings.

Conclusion: We conclude that, similar to eIF3h, RPL24B bolsters the reinitiation competence of uORF-translating ribosomes. Coordination between eIF3 and the large ribosomal subunit helps to fine-tune translation of uORF-containing mRNAs and, in turn, to orchestrate plant development.

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The 5' leaders of many uORF-containing ARF mRNAs render translation dependent on eIF3h. (A) Schematic view of the mRNAs for protoplast transformation. Open arrows represent RLUC ORF, hatched arrows represent codon-optimized FLUC (LUC+). mRNAs were prepared by in vitro transcription with SP6 RNA polymerase. An equal amount of internal control (Spacer-LUC+) mRNA was added to the 5' leader-RLUC mRNA to be tested as an internal control for transformation efficiency. (B and C) Translational efficiency on the given ARF 5' leader is expressed as the mean RLUC/FLUC ratio with standard errors from three replicate transformations. Data from several other auxin related 5' leaders are shown for comparison. PIN1 does not contain uORFs. AUX1 and TIR1 each have one short uORF of six codons.
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Figure 6: The 5' leaders of many uORF-containing ARF mRNAs render translation dependent on eIF3h. (A) Schematic view of the mRNAs for protoplast transformation. Open arrows represent RLUC ORF, hatched arrows represent codon-optimized FLUC (LUC+). mRNAs were prepared by in vitro transcription with SP6 RNA polymerase. An equal amount of internal control (Spacer-LUC+) mRNA was added to the 5' leader-RLUC mRNA to be tested as an internal control for transformation efficiency. (B and C) Translational efficiency on the given ARF 5' leader is expressed as the mean RLUC/FLUC ratio with standard errors from three replicate transformations. Data from several other auxin related 5' leaders are shown for comparison. PIN1 does not contain uORFs. AUX1 and TIR1 each have one short uORF of six codons.

Mentions: A protoplast transformation assay based on in vitro transcribed mRNA was adopted to observe the translation efficiency of specific mRNA 5' leaders in the eif3h mutant. While translation with a PIN1 leader, which lacks uORFs, or TIR1 and AUX1 leaders with only one short uORF, was not dramatically affected, the ARF leaders with multiple uORFs were poorly translated in the eif3h mutant (Fig. 6B, C). Translation of ARF3 and ARF5 were previously shown to be dependent on RPL24B. Results shown here now indicate that both eIF3h and RPL24B are required for maximal translation of the same target mRNA.


Translation reinitiation and development are compromised in similar ways by mutations in translation initiation factor eIF3h and the ribosomal protein RPL24.

Zhou F, Roy B, von Arnim AG - BMC Plant Biol. (2010)

The 5' leaders of many uORF-containing ARF mRNAs render translation dependent on eIF3h. (A) Schematic view of the mRNAs for protoplast transformation. Open arrows represent RLUC ORF, hatched arrows represent codon-optimized FLUC (LUC+). mRNAs were prepared by in vitro transcription with SP6 RNA polymerase. An equal amount of internal control (Spacer-LUC+) mRNA was added to the 5' leader-RLUC mRNA to be tested as an internal control for transformation efficiency. (B and C) Translational efficiency on the given ARF 5' leader is expressed as the mean RLUC/FLUC ratio with standard errors from three replicate transformations. Data from several other auxin related 5' leaders are shown for comparison. PIN1 does not contain uORFs. AUX1 and TIR1 each have one short uORF of six codons.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3020687&req=5

Figure 6: The 5' leaders of many uORF-containing ARF mRNAs render translation dependent on eIF3h. (A) Schematic view of the mRNAs for protoplast transformation. Open arrows represent RLUC ORF, hatched arrows represent codon-optimized FLUC (LUC+). mRNAs were prepared by in vitro transcription with SP6 RNA polymerase. An equal amount of internal control (Spacer-LUC+) mRNA was added to the 5' leader-RLUC mRNA to be tested as an internal control for transformation efficiency. (B and C) Translational efficiency on the given ARF 5' leader is expressed as the mean RLUC/FLUC ratio with standard errors from three replicate transformations. Data from several other auxin related 5' leaders are shown for comparison. PIN1 does not contain uORFs. AUX1 and TIR1 each have one short uORF of six codons.
Mentions: A protoplast transformation assay based on in vitro transcribed mRNA was adopted to observe the translation efficiency of specific mRNA 5' leaders in the eif3h mutant. While translation with a PIN1 leader, which lacks uORFs, or TIR1 and AUX1 leaders with only one short uORF, was not dramatically affected, the ARF leaders with multiple uORFs were poorly translated in the eif3h mutant (Fig. 6B, C). Translation of ARF3 and ARF5 were previously shown to be dependent on RPL24B. Results shown here now indicate that both eIF3h and RPL24B are required for maximal translation of the same target mRNA.

Bottom Line: Like AtbZip11, the uORF-containing ARF mRNAs are indeed undertranslated in eif3h mutant seedlings.We conclude that, similar to eIF3h, RPL24B bolsters the reinitiation competence of uORF-translating ribosomes.Coordination between eIF3 and the large ribosomal subunit helps to fine-tune translation of uORF-containing mRNAs and, in turn, to orchestrate plant development.

View Article: PubMed Central - HTML - PubMed

Affiliation: Genome Science and Technology Program, The University of Tennessee, Knoxville, TN 37996, USA.

ABSTRACT

Background: Within the scanning model of translation initiation, reinitiation is a non-canonical mechanism that operates on mRNAs harboring upstream open reading frames. The h subunit of eukaryotic initiation factor 3 (eIF3) boosts translation reinitiation on the uORF-containing mRNA coding for the Arabidopsis bZip transcription factor, AtbZip11, among others. The RPL24B protein of the large ribosomal subunit, which is encoded by SHORT VALVE1, likewise fosters translation of uORF-containing mRNAs, for example mRNAs for auxin response transcription factors (ARFs).

Results: Here we tested the hypothesis that RPL24B and eIF3h affect translation reinitiation in a similar fashion. First, like eif3h mutants, rpl24b mutants under-translate the AtbZip11 mRNA, and the detailed spectrum of translational defects in rpl24b is remarkably similar to that of eif3h. Second, eif3h mutants display defects in auxin mediated organogenesis and gene expression, similar to rpl24b. Like AtbZip11, the uORF-containing ARF mRNAs are indeed undertranslated in eif3h mutant seedlings.

Conclusion: We conclude that, similar to eIF3h, RPL24B bolsters the reinitiation competence of uORF-translating ribosomes. Coordination between eIF3 and the large ribosomal subunit helps to fine-tune translation of uORF-containing mRNAs and, in turn, to orchestrate plant development.

Show MeSH
Related in: MedlinePlus