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Nucleic Acids Res. 2008 Aug;36(13):4233-41. doi: 10.1093/nar/gkn395. Epub 2008 Jun 25.

Minigene-like inhibition of protein synthesis mediated by hungry codons near the start codon.

Author information

1
Departamento de Genética y Biología Molecular, Centro de Investigación y de Estudios Avanzados del IPN, Apartado Postal 14-740, México DF, 07000, México.

Abstract

Rare AGA or AGG codons close to the initiation codon inhibit protein synthesis by a tRNA-sequestering mechanism as toxic minigenes do. To further understand this mechanism, a parallel analysis of protein synthesis and peptidyl-tRNA accumulation was performed using both a set of lacZ constructs where AGAAGA codons were moved codon by codon from +2, +3 up to +7, +8 positions and a series of 3-8 codon minigenes containing AGAAGA codons before the stop codon. Beta-galactosidase synthesis from the AGAAGA lacZ constructs (in a Pth defective in vitro system without exogenous tRNA) diminished as the AGAAGA codons were closer to AUG codon. Likewise, beta-galactosidase expression from the reporter +7 AGA lacZ gene (plus tRNA, 0.25 microg/microl) waned as the AGAAGAUAA minigene shortened. Pth counteracted both the length-dependent minigene effect on the expression of beta-galactosidase from the +7 AGA lacZ reporter gene and the positional effect from the AGAAGA lacZ constructs. The +2, +3 AGAAGA lacZ construct and the shortest +2, +3 AGAAGAUAA minigene accumulated the highest percentage of peptidyl-tRNA(Arg4). These observations lead us to propose that hungry codons at early positions, albeit with less strength, inhibit protein synthesis by a minigene-like mechanism involving accumulation of peptidyl-tRNA.

PMID:
18583364
PMCID:
PMC2490762
DOI:
10.1093/nar/gkn395
[Indexed for MEDLINE]
Free PMC Article

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