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Conjugative Mating Assays for Sequence-specific Analysis of Transfer Proteins Involved in Bacterial Conjugation
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tRNA is a new target for cleavage by a MazF toxin

Jason M Schifano1, Jonathan W Cruz1, Irina O Vvedenskaya2

  • 1Department of Biochemistry and Molecular Biology, Rutgers University, Robert Wood Johnson Medical School, Piscataway, NJ, USA.

Nucleic Acids Research
|January 8, 2016
PubMed

Insights

Mycobacterium tuberculosis toxin MazF-mt9 uniquely targets and cleaves specific bacterial tRNAs, impacting bacterial growth. This discovery reveals a novel mechanism for toxin-antitoxin systems and bacterial stress response.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Bacterial Genetics

Background:

  • Toxin-antitoxin (TA) systems are crucial for bacterial survival under stress.
  • The MazF toxin, typically an mRNA-targeting endoribonuclease, has diverse roles in bacterial persistence and biofilm formation.
  • Previous research suggested MazF toxins exclusively cleave mRNA, though some evidence indicated rRNA cleavage.

Purpose of the Study:

  • To identify the specific RNA targets of the Mycobacterium tuberculosis toxin MazF-mt9.
  • To elucidate the mechanism of RNA recognition and cleavage by MazF-mt9.
  • To explore the functional implications of MazF-mt9 activity on bacterial growth and stress response.

Main Methods:

  • RNA sequencing (RNA-seq) based approach to profile RNA cleavage.
  • Biochemical assays to confirm target specificity and cleavage sites.
  • Comparative analysis with known MazF toxins and eukaryotic tRNases.

Main Results:

  • MazF-mt9 was found to primarily cleave two specific transfer RNAs (tRNAs): tRNA(Pro14) and tRNA(Lys43).
  • Cleavage occurred at single, distinct sites within the D-loop of tRNA(Pro14) and the anticodon of tRNA(Lys43).
  • Target recognition involved both sequence and structural RNA determinants, a novel feature for MazF toxins.

Conclusions:

  • MazF-mt9 is the first identified MazF family member that targets tRNA and requires RNA structure for cleavage.
  • The tRNase activity of MazF-mt9 shares similarities with eukaryotic tRNases involved in stress-induced translational inhibition.
  • Cleavage of tRNA by MazF-mt9 suggests a non-canonical role for tRNA in bacterial growth regulation during stress.

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