Macromolecules II May 4, 2009 Jane Yu Transfer-messenger RNA
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 post-translation
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
tmRNA also: 1) mediates degradation of the aberrant mRNA 2) adds a degradation tag to the aberrant protein for directed proteolysis Functions of tmRNA
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)