Toxin-mediated ribosome stalling reprograms the Mycobacterium tuberculosis proteome

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Mycobacterium tuberculosis (TB) exhibits remarkable adaptability to survive host defenses and establish latent infections.
• Stress survival in M. tuberculosis involves complex physiological and regulatory mechanisms.

Purpose of the Study:

• To elucidate a novel regulatory mechanism employed by M. tuberculosis for stress adaptation.
• To investigate the role of the tRNA-cleaving toxin MazF-mt9 in modulating gene expression and protein synthesis.

Main Methods:

• Identification and characterization of the tRNA-cleaving toxin MazF-mt9.
• Analysis of tRNA inactivation and its impact on ribosome function using specific lysine tRNAs (tRNA ^Lys43-UUU and tRNA ^Lys19-CUU).
• Transcriptome and proteome analysis to assess changes in gene expression and protein profiles.

Main Results:

• MazF-mt9 selectively cleaves tRNA ^Lys43-UUU at the anticodon (UU ↓ U), preventing its function.
• Loss of tRNA ^Lys43-UUU leads to ribosome stalling at AAA Lys codons due to inability of tRNA ^Lys19-CUU to compensate.
• Stalled ribosomes trigger selective RNase-mediated cleavage and deletion of cognate transcripts, altering the transcriptome.
• This leads to a skewed proteome, favoring proteins with fewer AAA Lys codons.

Conclusions:

• Toxin-mediated tRNA inactivation and ribosome stalling represent a sophisticated regulatory strategy in M. tuberculosis.
• This mechanism allows for selective transcriptome and proteome remodeling, enhancing bacterial stress survival.
• The findings provide insights into the molecular basis of latent TB infection and potential therapeutic targets.