GUG is an efficient initiation codon to translate the human mitochondrial ATP6 gene

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Mitochondrial DNA (mtDNA) mutations are linked to various diseases.
• The ATP6 gene encodes ATPase subunit a, crucial for mitochondrial function.
• Initiation codons (AUG) are essential for protein translation.

Observation:

• A specific mtDNA mutation (8527A>G) was identified, changing the AUG initiation codon to GUG.
• The mutation was maternally inherited and present in a patient with suspected mitochondrial disease, but not in their healthy mother.
• The mutation was absent in controls and rare in patients with Leber Hereditary Optic Neuropathy (LHON) lacking typical mutations.

Findings:

• No significant impact of the 8527A>G mutation was observed on mtDNA-encoded protein biosynthesis, ATPase subunit a levels, ATP hydrolysis, or mitochondrial membrane potential in patient fibroblasts.
• ATP synthesis was only minimally reduced despite the altered initiation codon.
• This indicates that GUG can function as a valid initiation codon for the human ATP6 gene.

Implications:

• The study challenges the strict requirement of AUG as the sole initiation codon for the human ATP6 gene.
• It suggests that certain mtDNA mutations altering initiation codons may not always result in severe mitochondrial dysfunction.
• This finding has implications for understanding the pathogenicity of mtDNA mutations and diagnosing mitochondrial disorders.