Pathology-related substitutions in human mitochondrial tRNA(Ile) reduce precursor 3' end processing efficiency in...

Area of Science:

• Mitochondrial genetics
• Molecular biology
• Human genetics

Background:

• The human mitochondrial genome contains 22 transfer RNAs (tRNAs) essential for protein synthesis.
• Mutations in mitochondrial tRNAs are linked to various maternally inherited diseases, often due to impaired tRNA metabolism.
• Efficient excision of tRNAs from precursor molecules is crucial for mitochondrial function.

Purpose of the Study:

• To investigate the impact of pathogenic mutations on the 3' end maturation of mitochondrial tRNA(Ile) precursors.
• To determine how these mutations affect the efficiency of 3'-tRNase processing.
• To analyze the structural consequences of mutations on tRNA(Ile) precursor folding.

Main Methods:

• In vitro processing assays using 3'-tRNase to measure the efficiency of tRNA(Ile) precursor maturation.
• Kinetic analysis (Vmax / KM) to quantify the effect of mutations on processing rates.
• Secondary structure probing to assess the structural integrity of wild-type and mutant tRNA(Ile) precursors.

Main Results:

• Four pathogenic tRNA(Ile) mutations significantly reduced 3'-tRNase processing efficiency by approximately 10-fold compared to wild-type.
• The reduced efficiency was primarily due to a lower Vmax, indicating impaired catalytic turnover.
• The G4309A mutation altered the secondary structure of the tRNA(Ile) precursor, particularly in the T domain, while others maintained a canonical cloverleaf structure.

Conclusions:

• Impaired 3' end processing of tRNA(Ile) precursors, caused by specific pathogenic mutations, can contribute to human mitochondrial diseases.
• Structural perturbations in tRNA precursors, as seen with the G4309A mutation, may underlie processing defects.
• These findings highlight the critical role of efficient tRNA maturation in preventing mitochondrial dysfunction and disease.