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Transfer-messenger RNA
Macromolecules II
May 4, 2009
Jane Yu
Discovery of tmRNA
a small, stable RNA
Ray and Apirion, 1979
Jain, et al. 1982
Where is tmRNA found?
• All sequenced eubacteria
• Some rare mitochondrial and
plastidial genomes in simple
eukaryotes such as diatoms.
• Some phage genomes
• No nuclear genomes
What is tmRNA?
mRNA-like and tRNA-like properties
Structure of tmRNA
Ribosomal RNA is normally recycled posttranslation
tmRNA “rescues” ribosomes stalled during
translation of mRNA lacking stop codons.
A ribosome stuck with nonstop RNA
tmRNA “rescues” ribosomes stalled during
translation of mRNA lacking stop codons.
A sad ribosome stuck with nonstop RNA
Functions of tmRNA
tmRNA also:
1) mediates degradation of the aberrant mRNA
2) adds a degradation tag to the aberrant protein
for directed proteolysis
The tmRNA/SmpB complex
Trans-translation
Role in human disease
Vital for normal growth in:
Mycobacterium pneumoniae
Neisseria gonorrhaeae
Vital for pathogenesis in:
Salmonella typhimurium (MP survival)
Yersinia pseudotuberculosis (T3SS)