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.