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RNase R degrades non-stop mRNAs selectively in an SmpB-tmRNA-dependent manner

Jamie Richards1, Preeti Mehta, A Wall Karzai

  • 1Department of Biochemistry and Cell Biology, Center for Infectious Diseases of Stony Brook University, Stony Brook, NY 11794, USA.

Molecular Microbiology
|November 8, 2006
PubMed

Insights

The trans-translation system uses SmpB-tmRNA to rescue stalled ribosomes and degrade non-stop mRNAs. RNase R is essential for this mRNA decay, working with SmpB and tmRNA.

Area of Science:

  • Molecular Biology
  • RNA Biology
  • Bacterial Genetics

Background:

  • The SmpB-tmRNA system rescues stalled ribosomes and targets proteins for degradation.
  • Non-stop mRNAs, which lack stop codons, are known to be degraded, but the mechanism is unclear.

Purpose of the Study:

  • To elucidate the mechanism and identify RNases involved in the degradation of non-stop mRNAs.
  • To investigate the role of trans-translation in non-stop mRNA decay.

Main Methods:

  • Utilized Escherichia coli as a model organism.
  • Investigated the requirement for RNase R, SmpB protein, and tmRNA in non-stop mRNA decay.
  • Assessed the roles of RNase II and PNPase in the tmRNA-mediated mRNA disposal pathway.

Main Results:

  • RNase R activity is essential for non-stop mRNA decay, dependent on SmpB and tmRNA.
  • Trans-translation facilitates RNase R engagement and promotes non-stop mRNA decay.
  • RNase R selectively degrades aberrant mRNAs (non-stop and rare-codon containing) but not those with stop codons.
  • RNase II and PNPase play minor roles in this tmRNA-facilitated mRNA decay.

Conclusions:

  • RNase R is a key enzyme in the trans-translation-mediated degradation of non-stop mRNAs.
  • This pathway complements the ribosome rescue and protein tagging functions of the SmpB-tmRNA system.
  • Identified a specific RNase responsible for clearing aberrant transcripts, enhancing cellular quality control.

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