POLRMT overexpression increases mtDNA transcription without affecting steady-state mRNA levels

Area of Science:

• Mitochondrial Biology
• Molecular Genetics
• Biochemistry

Background:

• Mitochondrial RNA polymerase (POLRMT) is crucial for mitochondrial DNA (mtDNA) transcription and replication.
• Elevated POLRMT levels are observed in cancers and mitochondrial dysfunction models.
• The physiological impact of increased POLRMT is not fully understood.

Purpose of the Study:

• To investigate the consequences of elevated POLRMT levels using a mouse model.
• To explore the relationship between POLRMT, mtDNA transcription, and oxidative phosphorylation (OXPHOS).

Main Methods:

• Generation and characterization of mice overexpressing Polrmt.
• Analysis of mtDNA transcription initiation and RNA levels.
• Assessment of physiological parameters, including exercise performance.

Main Results:

• Polrmt overexpression did not cause pathological phenotypes.
• Male mice overexpressing Polrmt showed enhanced exercise performance under stress.
• Increased POLRMT led to higher initiation of mtDNA transcription and 7S RNA levels.
• Mature mitochondrial RNA abundance remained unaffected, even when co-overexpressing Lrpprc.

Conclusions:

• POLRMT levels regulate mitochondrial transcription initiation.
• Downstream regulatory steps and transcript stability limit OXPHOS biogenesis.
• Mitochondrial RNA processing and stability are key factors in regulating gene expression.