Innate immune and chemically triggered oxidative stress modifies translational fidelity.
Translational fidelity, essential for protein and cell function, requires accurate transfer RNA (tRNA) aminoacylation. Purified aminoacyl-tRNA synthetases exhibit a fidelity of one error per 10,000 to 100,000 couplings. The accuracy of tRNA aminoacylation in vivo is uncertain, however, and might be considerably lower. Here we show that in mammalian cells, approximately 1% of methionine (Met) residues used in protein synthesis are aminoacylated to non-methionyl-tRNAs. Remarkably, Met-misacylation increases up to tenfold upon exposing cells to live or non-infectious viruses, toll-like receptor ligands or chemically induced oxidative stress. Met is misacylated to specific non-methionyl-tRNA families, and these Met-misacylated tRNAs are used in translation. Met-misacylation is blocked by an inhibitor of cellular oxidases, implicating reactive oxygen species (ROS) as the misacylation trigger. Among six amino acids tested, tRNA misacylation occurs exclusively with Met. As Met residues are known to protect proteins against ROS-mediated damage, we propose that Met-misacylation functions adaptively to increase Met incorporation into proteins to protect cells against oxidative stress. In demonstrating an unexpected conditional aspect of decoding mRNA, our findings illustrate the importance of considering alternative iterations of the genetic code.
Netzer
Nir
N
Laboratory of Viral Diseases, National Institute of Allergy and Infectious Diseases, Bethesda, Maryland 20892, USA.
Goodenbour
Jeffrey M
JM
David
Alexandre
A
Dittmar
Kimberly A
KA
Jones
Richard B
RB
Schneider
Jeffrey R
JR
Boone
David
D
Eves
Eva M
EM
Rosner
Marsha R
MR
Gibbs
James S
JS
Embry
Alan
A
Dolan
Brian
B
Das
Suman
S
Hickman
Heather D
HD
Berglund
Peter
P
Bennink
Jack R
JR
Yewdell
Jonathan W
JW
Pan
Tao
T
D000256:Adenoviridae / Q000502:physiology; D000818:Animals; D005815:Genetic Code; D006367:HeLa Cells; D006801:Humans; D007113:Immunity, Innate; D008024:Ligands; D008715:Methionine / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008957:Models, Genetic; D019255:NADPH Oxidases / Q000378:metabolism; D009975:Orthomyxoviridae / Q000502:physiology; D018384:Oxidative Stress / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D012358:RNA, Transfer, Met / Q000235:genetics / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013379:Substrate Specificity; D051193:Toll-Like Receptors / Q000276:immunology / Q000378:metabolism; D046249:Transfer RNA Aminoacylation / Q000187:drug effects / Q000502:physiology*
D008024:Ligands; D012358:RNA, Transfer, Met; D017382:Reactive Oxygen Species; D051193:Toll-Like Receptors; D008715:Methionine; D019255:NADPH Oxidases