Autophagy determines mtDNA copy number dynamics during starvation.

Area of Science:

• Cellular Biology
• Genetics
• Molecular Biology

Background:

• Mitochondria possess their own genome (mtDNA), crucial for cellular function.
• Regulation of mitochondrial DNA (mtDNA) copy number remains incompletely understood.
• mtDNA exists in multiple copies within nucleoprotein complexes called nucleoids.

Purpose of the Study:

• To elucidate the mechanisms controlling mitochondrial DNA copy number.
• To investigate the role of Mip1/POLG in mtDNA copy number regulation.
• To understand the impact of nutrient starvation and autophagy on mtDNA homeostasis.

Main Methods:

• Utilized yeast models to study mitochondrial DNA dynamics.
• Investigated the dual functions of Mip1/POLG in mtDNA synthesis and degradation.
• Assessed the role of macroautophagy/autophagy in maintaining mtDNA integrity.

Main Results:

• Mip1/POLG acts as a critical regulator of mtDNA copy number through opposing synthesis and degradation modes.
• Autophagy integrity is essential for sustaining mtDNA synthesis and maintenance.
• Autophagy deficiency leads to impaired mtDNA synthesis, increased degradation, and respiratory deficiency due to nucleotide insufficiency and ROS.

Conclusions:

• Mip1/POLG plays a pivotal role in balancing mtDNA synthesis and degradation.
• Autophagy is indispensable for maintaining mitochondrial genome stability under nutrient stress.
• Disruption of autophagy leads to severe mitochondrial dysfunction and genome depletion.