tRNA-mediated codon-biased translation in mycobacterial hypoxic persistence

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Microbial pathogens adapt to infection stress by regulating gene expression, translation, and protein modification.
• Mycobacteria, like Mycobacterium bovis BCG, exhibit non-replicating persistence under hypoxic conditions, a state relevant to tuberculous granulomas.

Purpose of the Study:

• To investigate the role of tRNA reprogramming and codon-biased translation in mycobacterial adaptation to hypoxia.
• To understand how these mechanisms contribute to the expression of stress response genes during infection.

Main Methods:

• Analysis of tRNA modifications in Mycobacterium bovis BCG under various oxygen conditions (hypoxia and aerobic resuscitation).
• Correlation of tRNA reprogramming with the selective translation of specific messenger RNAs (mRNAs).
• Genetic manipulation of the dosR gene to assess its impact on hypoxia-induced translation and bacterial survival.

Main Results:

• Mycobacterium bovis BCG uniquely reprogrammed 40 modified ribonucleosides in tRNA during different stages of hypoxia and resuscitation.
• These tRNA modifications correlated with the preferential translation of mRNAs from codon-biased gene families, including the DosR regulator.
• Engineering the dosR gene's codons altered DosR translation and significantly impacted bacterial survival during hypoxia.

Conclusions:

• A coordinated system of tRNA modifications and codon-biased translation regulates the expression of stress response proteins in mycobacteria.
• This mechanism is crucial for bacterial adaptation and survival under hypoxic stress, such as that encountered in tuberculous granulomas.