Disease-associated mutations in mitochondrial precursor tRNAs affect binding, m1R9 methylation, and tRNA processing...

Area of Science:

• Mitochondrial biology
• Molecular genetics
• Biochemistry

Background:

• Mitochondrial diseases are often caused by mutations in mitochondrial tRNA genes, but their precise contribution to disease is unclear.
• Mitochondrial tRNA processing involves enzymes like mtRNase P, which removes the 5' leader sequence and methylates specific bases.
• The role of mtRNase P in disease pathogenesis remains largely unexplored.

Purpose of the Study:

• To investigate the impact of 11 disease-linked mutations in mitochondrial precursor tRNAs (pre-tRNAs) on mtRNase P activity.
• To determine how these mutations affect pre-tRNA binding, 5' end processing, and methylation.
• To explore the link between altered tRNA processing and mitochondrial dysfunction.

Main Methods:

• In vitro assays were used to assess the binding affinity of mtRNase P to mutated pre-tRNAs.
• Enzyme activity assays measured the 5' end processing and methylation capabilities of mtRNase P with mutant substrates.
• Structural analysis was performed on mutated mitochondrial tRNAs to assess their fold.

Main Results:

• Several mutations significantly weakened the binding affinity of mtRNase P to pre-tRNAs.
• The majority of mutations reduced the 5' end processing and methylation activities of mtRNase P by up to 55% and 90%, respectively.
• Mutations in mitochondrial pre-tRNA^Leu(UUR) altered tRNA folding, contributing to reduced mtRNase P function.

Conclusions:

• Disease-linked mutations in mitochondrial pre-tRNAs disrupt their processing by mtRNase P.
• Impaired tRNA maturation, including altered binding, reduced enzymatic activity, and structural changes, contributes to mitochondrial dysfunction.
• This study establishes an etiological link between early mitochondrial tRNA processing defects and the development of mitochondrial diseases.