Abstract
During mRNA translation, synonymous codons for one amino acid are
often read by different isoaccepting tRNAs. The theory of selective tRNA
charging predicts greatly varying percentages of aminoacylation among
isoacceptors in cells starved for their common amino acid. It also predicts
major changes in tRNA charging patterns upon concentration changes of
single isoacceptors, which suggests a novel type of translational control of
gene expression. We therefore tested the theory by measuring with
Northern blots the charging of Leu-tRNAs in Escherichia coli under Leu
limitation in response to over expression of tRNALeu
GAG. As predicted, the
charged level of tRNALeu
GAG increased and the charged levels of four other
Leu isoacceptors decreased or remained unchanged, but the charged level
of tRNALeu
UAG increased unexpectedly. To remove this apparent inconsistency
between theory and experiment we postulated a previously
unknown common codon for tRNALeu
GAG and tRNALeu
UAG. Subsequently, we
demonstrated that the tRNALeu
GAG codon CUU is, in fact, read also by
tRNALeu
UAG, due to a uridine-5-oxyacetic acid modification.
| Original language | English |
|---|---|
| Journal | Journal of Molecular Biology |
| Volume | 354 |
| Issue number | 1 |
| Pages (from-to) | 16-24 |
| ISSN | 0022-2836 |
| DOIs | |
| Publication status | Published - 2005 |