Mycobacterial toxin MazF-mt6 inhibits translation through cleavage of 23S rRNA at the ribosomal A site

Jason M. Schifano, Regina Edifor, Jared D. Sharp, Ming Ouyang, Arvind Konkimalla, Robert N. Husson, Nancy A. Woychik

Research output: Contribution to journalArticlepeer-review

82 Scopus citations

Abstract

The Mycobacterium tuberculosis genome contains an unusually high number of toxin-antitoxin modules, some of which have been suggested to play a role in the establishment and maintenance of latent tuberculosis. Nine of these toxin-antitoxin loci belong to the mazEF family, encoding the intracellular toxin MazF and its antitoxin inhibitor MazE. Nearly every MazF ortholog recognizes a unique three- or five-base RNA sequence and cleaves mRNA. As a result, these toxins selectively target a subset of the transcriptome for degradation and are known as "mRNA interferases." Here we demonstrate that a MazF family member from M. tuberculosis, MazF-mt6, has an additional role-inhibiting translation through targeted cleavage of 23S rRNA in the evolutionarily conserved helix/ loop 70. We first determined that MazF-mt6 cleaves mRNA at 5'UU↓CCU3' sequences. We then discovered that MazF-mt6 also cleaves M. tuberculosis 23S rRNA at a single UUCCU in the ribosomal A site that contacts tRNA and ribosome recycling factor. To gain further mechanistic insight, we demonstrated that MazFmt6- mediated cleavage of rRNA can inhibit protein synthesis in the absence of mRNA cleavage. Finally, consistent with the position of 23S rRNA cleavage, MazF-mt6 destabilized 50S-30S ribosomal subunit association. Collectively, these results show that MazF toxins do not universally act as mRNA interferases, because MazF-mt6 inhibits protein synthesis by cleaving 23S rRNA in the ribosome active center.

Original languageEnglish (US)
Pages (from-to)8501-8506
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume110
Issue number21
DOIs
StatePublished - May 21 2013

All Science Journal Classification (ASJC) codes

  • General

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