Sequence and structure analysis of a mirror tRNA located upstream of the cytochrome oxidase I mRNA in mouse mitochondria.

RNA fragments corresponding to the mirror tRNA that is located upstream of the cytochrome oxidase I (COXI) gene in the mouse mitochondrial genome were found in the sequences obtained from the mouse brain by the next generation sequencing. RNA fragments corresponding to the 5' terminal of COXI mRNA were also found and it was suggested that the precursor of the COXI mRNA is processed at three residues upstream of the first AUG codon. The mirror tRNA fragment has poly(A) in its 3' terminal and variable 5' terminal, suggesting that this RNA is produced during the 5' processing of COXI mRNA. Secondary structure prediction and NMR analysis indicated that the mirror tRNA is folded into a tRNA-like secondary structure, suggesting that the tRNA-like conformation of the 5' adjacent sequence of COXI mRNA is involved in the COXI mRNA maturation in the mouse mitochondria.