Author response: Oxidation of cellular amino acid pools leads to cytotoxic mistranslation of the genetic code

Accurate translation of the genetic information from DNA to protein is maintained by multiple quality control steps from bacteria to mammals. Genetic and environmental alterations have been shown to compromise translational quality control and reduce fidelity during protein synthesis. The physiological impact of increased translational errors is not fully understood. While generally considered harmful, translational errors have recently been shown to benefit cells under certain stress conditions. In this work, we describe a novel regulatory pathway in which reduced translational fidelity downregulates expression of flagellar genes and suppresses bacterial motility. Electron microscopy imaging shows that the error-prone Escherichia coli strain lacks mature flagella. Further genetic analyses reveal that translational errors upregulate expression of a small RNA DsrA through enhancing its transcription, and deleting DsrA from the error-prone strain restores motility. DsrA regulates expression of H-NS and RpoS, both of which regulate flagellar genes. We demonstrate that an increased level of DsrA in the error-prone strain suppresses motility through the H-NS pathway. Our work suggests that bacteria are capable of switching on and off the flagellar system by altering translational fidelity, which may serve as a previously unknown mechanism to improve fitness in response to environmental cues.

show abstract

Multiple Quality Control Pathways Limit Non-protein Amino Acid Use by Yeast Cytoplasmic Phenylalanyl-tRNA Synthetase

Moghal

Hwang

Faull

et al. 2016

Journal of Biological Chemistry

Self Cite

View full text Add to dashboard Cite

Non-protein amino acids, particularly isomers of the proteinogenic amino acids, present a threat to proteome integrity if they are mistakenly inserted into proteins. Quality control during aminoacyl-tRNA synthesis reduces non-protein amino acid incorporation by both substrate discrimination and proofreading. For example phenylalanyl-tRNA synthetase (PheRS) proofreads the non-protein hydroxylated phenylalanine derivative m-Tyr after its attachment to tRNA Phe . We now show in Saccharomyces cerevisiae that PheRS misacylation of tRNA Phe with the more abundant Phe oxidation product o-Tyr is limited by kinetic discrimination against o-Tyr-AMP in the transfer step followed by o-Tyr-AMP release from the synthetic active site. This selective rejection of a non-protein aminoacyl-adenylate is in addition to known kinetic discrimination against certain noncognates in the activation step as well as catalytic hydrolysis of mispaired aminoacyl-tRNA Phe species. We also report an unexpected resistance to cytotoxicity by a S. cerevisiae mutant with ablated post-transfer editing activity when supplemented with o-Tyr, cognate Phe, or Ala, the latter of which is not a substrate for activation by this enzyme. Our phenotypic, metabolomic, and kinetic analyses indicate at least three modes of discrimination against non-protein amino acids by S. cerevisiae PheRS and support a non-canonical role for SccytoPheRS post-transfer editing in response to amino acid stress.

show abstract

Author response: Oxidation of cellular amino acid pools leads to cytotoxic mistranslation of the genetic code

Cited by 4 publications

References 0 publications

Translational quality control and reprogramming during stress adaptation

Translational quality control and reprogramming during stress adaptation

Reduced Protein Synthesis Fidelity Inhibits Flagellar Biosynthesis and Motility

Multiple Quality Control Pathways Limit Non-protein Amino Acid Use by Yeast Cytoplasmic Phenylalanyl-tRNA Synthetase

Contact Info

Product

Resources

About