Initiation with Elongator tRNAs
| Autor: | Jaanus Remme, Laasya Samhita, Kai Virumäe, Umesh Varshney |
|---|---|
| Rok vydání: | 2013 |
| Předmět: |
RNA
Transfer Met Immunoblotting Peptide Chain Elongation Translational Codon Initiator Biology environment and public health Microbiology Ribosome RNA Transfer Start codon Anticodon Protein biosynthesis Cloning Molecular Peptide Chain Initiation Translational Molecular Biology Prokaryotic initiation factor Gene Microbiology & Cell Biology Genetics Escherichia coli K12 RNA Translation (biology) Articles Protein Biosynthesis Transfer RNA Ribosomes Plasmids |
| Zdroj: | Journal of Bacteriology. 195:4202-4209 |
| ISSN: | 0021-9193 |
| Popis: | In all domains of life, initiator tRNA functions exclusively at the first step of protein synthesis while elongator tRNAs extend the polypeptide chain. Unique features of initiator tRNA enable it to preferentially bind the ribosomal P site and initiate translation. Recently, we showed that the abundance of initiator tRNA also contributes to its specialized role. This motivates the question, can a cell also use elongator tRNA to initiate translation under certain conditions? To address this, we introduced non-AUG initiation codons CCC (Pro), GAG (Glu), GGU (Gly), UCU (Ser), UGU (Cys), ACG (Thr), AAU (Asn), and AGA (Arg) into the uracil DNA glycosylase gene (ung) used as a reporter gene. Enzyme assays from log-phase cells revealed initiation from non-AUG codons when intracellular initiator tRNA levels were reduced. The activity increased significantly in stationary phase. Further increases in initiation from non-AUG codons occurred in both growth phases upon introduction of plasmid-borne genes of cognate elongator tRNAs. Since purine-rich Shine-Dalgarno sequences occur frequently on mRNAs (in places other than the canonical AUG codon initiation contexts), initiation with elongator tRNAs from the alternate contexts may generate proteome diversity under stress without compromising genomic integrity. Thus, by changing the relative amounts of initiator and elongator tRNAs within the cell, we have blurred the distinction between the two classes of tRNAs thought to be frozen through years of evolution. |
| Databáze: | OpenAIRE |
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