Mitochondrial transcription termination factor 1 directs polar replication fork pausing.

Area of Science:

• Mitochondrial biology
• Molecular genetics
• Genomics

Background:

• Nuclear ribosomal DNA (rDNA) replication faces challenges from transcription machinery, necessitating replication fork barriers.
• Mitochondrial transcription termination factor 1 (MTERF1) is a candidate protein for a similar role in mitochondria, located downstream of the ribosomal transcription unit.

Purpose of the Study:

• To investigate the role of MTERF1 in mitochondrial DNA (mtDNA) replication.
• To determine if MTERF1 functions as a replication fork barrier in mammalian mitochondria.

Main Methods:

• Assessed MTERF1's effect on mtDNA replication polarity.
• Investigated MTERF1's interaction with the mitochondrial helicase TWINKLE.
• Utilized in vivo evidence to support MTERF1's role in TWINKLE pausing.

Main Results:

• MTERF1 arrests mtDNA replication with a distinct polarity.
• MTERF1 functions as a directional contrahelicase, inhibiting mtDNA unwinding by TWINKLE.
• In vivo data shows MTERF1 enhances TWINKLE pausing.

Conclusions:

• MTERF1 directs polar replication fork arrest in mammalian mitochondria.
• This mechanism prevents replication conflicts and maintains mitochondrial genome stability.