Inhibited cell growth and protein functional changes from an editing-defective tRNA synthetase

Aminoacyl-tRNA synthetases (ARSs) establish the rules of the genetic code, whereby each amino acid is attached to a cognate tRNA. Errors in this process lead to mistranslation, which can be toxic to cells. The selective forces exerted by species-specific requirements and environmental conditions potentially shape qualitycontrol mechanisms that serve to prevent mistranslation. A family of editing factors that are homologous to the editing domain of bacterial prolyl-tRNA synthetase includes the previously characterized trans-editing factors ProXp-ala and YbaK, which clear Ala-tRNA Pro and Cys-tRNA Pro , respectively, and three additional homologs of unknown function, ProXp-x, ProXp-y, and ProXp-z. We performed an in vivo screen of 230 conditions in which an Escherichia coli proXp-y deletion strain was grown in the presence of elevated levels of amino acids and specific ARSs. This screen, together with the results of in vitro deacylation assays, revealed Ser-and Thr-tRNA deacylase function for this homolog. A similar activity was demonstrated for Bordetella parapertussis ProXp-z in vitro. These proteins, now renamed "ProXp-ST1" and "ProXp-ST2," respectively, recognize multiple tRNAs as substrates. Taken together, our data suggest that these free-standing editing domains have the ability to prevent mistranslation errors caused by a number of ARSs, including lysyl-tRNA synthetase, threonyl-tRNA synthetase, seryl-tRNA synthetase, and alanyl-tRNA synthetase. The expression of these multifunctional enzymes is likely to provide a selective growth advantage to organisms subjected to environmental stresses and other conditions that alter the amino acid pool.aminoacyl tRNA synthetase | protein synthesis | ProXp | quality control | trans-editing

Section: Trans-editingmentioning

confidence: 99%

Homologous trans -editing factors with broad tRNA specificity prevent mistranslation caused by serine/threonine misactivation

Liu

Vargas-Rodriguez

Goto

et al. 2015

“…Simple single-cell prokaryotic organisms are apparently able to tolerate significant misreading (27,28), as also evidenced by the viability of the A1555G and C1494U hybrid mutants. However, the situation in complex multicellular eukaryotes and in highly specialized tissues is notably different.…”

Section: Figmentioning

confidence: 99%

Mitochondrial deafness alleles confer misreading of the genetic code

Hobbie

Bruell

Subramanian

et al. 2008

105

123

Despite the fact that important genetic diseases are caused by mutant mitochondrial ribosomes, the molecular mechanisms by which such ribosomes result in a clinical phenotype remain largely unknown. The absence of experimental models for mitochondrial diseases has also prevented the rational search for therapeutic interventions. Here, we report on the construction of bacterial hybrid ribosomes that contain various versions of the mitochondrial decoding region of ribosomal RNA. We show that the pathogenic mutations A1555G and C1494T decrease the accuracy of translation and render the ribosomal decoding site hypersusceptible to aminoglycoside antibiotics. This finding suggests misreading of the genetic code as an important molecular mechanism in disease pathogenesis.decoding ͉ mitochondria ͉ mutant rRNA ͉ ribosomes ͉ disease

“…This ileS Ala allele has a critical section of the coding sequence of the editing domain replaced with 11 codons for alanine. Relative to the isogenic wild-type strain, this strain had a diminished growth rate, was highly sensitive to a structural analogue of isoleucine, and had an increased sensitivity to antibiotics (4). Surprisingly, the editing-defective mutant was no more sensitive to mutagens and had no greater mutation frequency than the isogenic wild-type strain (4).…”

mentioning

confidence: 99%

“…Relative to the isogenic wild-type strain, this strain had a diminished growth rate, was highly sensitive to a structural analogue of isoleucine, and had an increased sensitivity to antibiotics (4). Surprisingly, the editing-defective mutant was no more sensitive to mutagens and had no greater mutation frequency than the isogenic wild-type strain (4). Given the gradual cellular degeneration observed in Purkinje cells in response to an editing-defective alanyl-tRNA synthetase (1), we wondered whether aging might also lead to accumulated genetic degeneration in a bacterial model system.…”

mentioning

confidence: 99%

An editing-defective aminoacyl-tRNA synthetase is mutagenic in aging bacteria via the SOS response

Bacher

Schimmel

2007

Self Cite

Mistranslation in bacterial and mammalian cells leads to production of statistical proteins that are, in turn, associated with specific cell or animal pathologies, including death of bacterial cells, apoptosis of mammalian cells in culture, and neurodegeneration in the mouse. A major source of mistranslation comes from heritable defects in the editing activities of aminoacyl-tRNA synthetases. These activities clear errors of aminoacylation by deacylation of mischarged tRNAs. We hypothesized that, in addition to previously reported phenotypes in bacterial and mammalian systems, errors of aminoacylation could be mutagenic and lead to disease. As a first step in testing this hypothesis, the effect of an editing defect in a single tRNA synthetase on the accumulation of mutations in aging bacteria was investigated. A striking, statistically significant, enhancement of the mutation rate in aging bacteria was found. This enhancement comes from an increase in error-prone DNA repair through induction of the bacterial SOS response. Thus, mistranslation, as caused by an editing-defective tRNA synthetase, can lead to heritable genetic changes that could, in principle, be linked to disease.aminoacylation errors ͉ error-prone DNA polymerases ͉ amino acid misincorporation ͉ genetic code ambiguity A s organisms age, mutations accumulate over time owing to direct environmental insults that are incompletely or inaccurately repaired. Recent work directed our attention to the possibility that mistranslation could play a role in producing mutations in aging populations. In particular, mistranslation can arise from editing defects in aminoacyl-tRNA synthetases. These enzymes catalyze the first step of protein synthesis, where each amino acid is linked to its cognate tRNA bearing the anticodon triplet associated with the amino acid. Because of inherent physiochemical limitations of some enzymes to discriminate between structurally similar amino acids, mischarged tRNAs, such as Val-tRNA Ile or Ser-tRNA Ala , are produced. Normally, these mischarged tRNAs are cleared by hydrolytic editing, which occurs at a distinct active site within the synthetase. But even a small defect, caused by a mutation in the editing center, can lead to extreme cell pathologies and disease.For example, mice that carry a mild mutation in the editing domain of alanyl-tRNA synthetase suffer from ataxia (1). The mutant alanyl-tRNA synthetase mischarges tRNA Ala with serine and, as a consequence, mistranslation occurs that leads to induction of the unfolded protein response. That, in turn, leads to the degeneration of Purkinje cells in the cerebellum, beginning within 3 weeks of age. Similarly, in human cell culture, an inducible, editing-defective valyl-tRNA synthetase caused cellular degradation and apoptosis (2).With these recent results in mind, we were motivated to investigate the possibility that mistranslation could also lead to heritable genetic changes. Previously, we generated a knock-in mutant allele of ileS that encodes no functional editing domain (3)....