The essential mycobacterial amidotransferase GatCAB is a modulator of specific translational fidelity

• Published in: Nature microbiology Vol. 1; no. 11; p. 16147
• Main Authors: Su, Hong-Wei, Zhu, Jun-Hao, Li, Hao, Cai, Rong-Jun, Ealand, Christopher, Wang, Xun, Chen, Yu-Xiang, Kayani, Masood ur Rehman, Zhu, Ting F., Moradigaravand, Danesh, Huang, Hairong, Kana, Bavesh D., Javid, Babak
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 26-08-2016; Nature Publishing Group
• Subjects: 631/326/22/1290; 631/326/41/2482; 631/326/421; Aminoacylation; Antibiotic tolerance; Asparagine; Asparagine - metabolism; Biomedical and Life Sciences; Clinical isolates; Codon; Codons; Drug Resistance, Bacterial - genetics; Escherichia coli - genetics; Fidelity; Genetic screening; Glutamine; Glutamine - metabolism; Glutamine amidotransferase; Infectious Diseases; letter; Life Sciences; Medical Microbiology; Microbiology; Mutation; Mycobacterium smegmatis - drug effects; Mycobacterium smegmatis - enzymology; Mycobacterium smegmatis - genetics; Nitrogenous Group Transferases - genetics; Nitrogenous Group Transferases - metabolism; Organelles; Parasitology; Protein Biosynthesis; Rifampin; Rifampin - pharmacology; Transcription; Transfer RNA Aminoacylation; Translation; tRNA; Tuberculosis; Virology
• ISSN: 2058-5276; 2058-5276
• DOI: 10.1038/nmicrobiol.2016.147

Although regulation of translation fidelity is an essential process
1
–
7
, diverse organisms and organelles have differing requirements of translational accuracy
8
–
15
, and errors in gene translation serve an adaptive function under certain conditions
16
–
20
. Therefore, optimal levels of fidelity may vary according to context. Most bacteria utilize a two-step pathway for the specific synthesis of aminoacylated glutamine and/or asparagine tRNAs, involving the glutamine amidotransferase GatCAB
21
–
25
, but it had not been appreciated that GatCAB may play a role in modulating mistranslation rates. Here, by using a forward genetic screen, we show that the mycobacterial GatCAB enzyme complex mediates the translational fidelity of glutamine and asparagine codons. We identify mutations in
gatA
that cause partial loss of function in the holoenzyme, with a consequent increase in rates of mistranslation. By monitoring single-cell transcription dynamics, we demonstrate that reduced
gatCAB
expression leads to increased mistranslation rates, which result in enhanced rifampicin-specific phenotypic resistance. Consistent with this, strains with mutations in
gatA
from clinical isolates of
Mycobacterium tuberculosis
show increased mistranslation, with associated antibiotic tolerance, suggesting a role for mistranslation as an adaptive strategy in tuberculosis. Together, our findings demonstrate a potential role for the indirect tRNA aminoacylation pathway in regulating translational fidelity and adaptive mistranslation.
The mycobacterial glutamine amidotransferase GatCAB complex mediates the translational fidelity of glutamine and asparagine codons and strains with mutations in gatA show increased mistranslation, with associated antibiotic tolerance.