page_title: Transfer-messenger RNA
section_title: mt-tmRNA processing and expression
hierarchical_section_title: Transfer-messenger RNA / Mitochondrial tmRNAs (ssrA gene) / mt-tmRNA processing and expression
caption_attribution_description: English: Processing of two-piece mt-tmRNA. The four major RNA processing sites are numbered (1-4). Processing at sites 1 and 4 is thought to occur by a tmRNA-specific activity, site 2 by RNase P and site 3 by a 3’ tRNA endonuclease processing. Nucleotides cleaved from the precursor are in gray; the post-transcriptionally added CCA is boxed.
context_page_description: Transfer-messenger RNA is a bacterial RNA molecule with dual tRNA-like and messenger RNA-like properties. The tmRNA forms a ribonucleoprotein complex together with Small Protein B, Elongation Factor Tu, and ribosomal protein S1. In trans-translation, tmRNA and its associated proteins bind to bacterial ribosomes which have stalled in the middle of protein biosynthesis, for example when reaching the end of a messenger RNA which has lost its stop codon. The tmRNA is remarkably versatile: it recycles the stalled ribosome, adds a proteolysis-inducing tag to the unfinished polypeptide, and facilitates the degradation of the aberrant messenger RNA. In the majority of bacteria these functions are carried out by standard one-piece tmRNAs. In other bacterial species, a permuted ssrA gene produces a two-piece tmRNA in which two separate RNA chains are joined by base-pairing.
context_section_description: RNA-Seq data of Phytophthora sojae show an expression level similar to that of neighboring mitochondrial tRNAs, and four major processing sites confirm the predicted termini of mature mt-tmRNA. The tmRNA precursor molecule is likely processed by RNase P and a tRNA 3’ processing endonuclease (see Figure 2); the latter activity is assumed to lead to the removal of the intervening sequence. Following the addition of CCA at the 3’ discriminator nucleotide, the tmRNA can be charged by alanyl-tRNA synthetase with alanine.
caption: Processing of two-piece mt-tmRNA. The four major RNA processing sites are numbered (1-4). Processing at sites 1 and 4 is thought to occur by a tmRNA-specific activity, site 2 by RNase P and site 3 by a 3’ tRNA endonuclease processing. Nucleotides cleaved from the precursor are in gray; the post-transcriptionally added CCA is boxed.
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