Ribonucleotides embedded in template DNA impair mitochondrial RNA polymerase progression

Area of Science:

• Mitochondrial Biology
• Molecular Genetics
• Biochemistry

Background:

• Human mitochondria lack pathways to repair misincorporated ribonucleotides (rNMPs) in their genome.
• While DNA polymerase can bypass single rNMPs, longer stretches impede DNA replication.

Purpose of the Study:

• To investigate the impact of embedded ribonucleotides (rNMPs) on mitochondrial transcription.
• To determine if the mitochondrial transcription elongation factor TEFM can overcome rNMP-induced stalling.

Main Methods:

• In vitro assays measuring mitochondrial RNA polymerase activity with varying rNMP incorporation in the template DNA.
• Testing the effect of the mitochondrial transcription elongation factor TEFM on stalled transcription.

Main Results:

• A single embedded rNMP in the template strand impairs mitochondrial RNA polymerase elongation.
• Consecutive rNMPs significantly aggravate the inhibitory effect on transcription.
• The mitochondrial transcription elongation factor TEFM could not overcome rNMP-induced transcriptional stalling.

Conclusions:

• Embedded rNMPs pose a significant obstacle to mitochondrial transcription, not just replication.
• Impaired mitochondrial transcription due to rNMPs may contribute to genetic disorders linked to nucleotide pool imbalances.