The human mitochondrial transcription factor A is a versatile G-quadruplex binding protein

Area of Science:

• Mitochondrial biology
• Molecular genetics
• Biochemistry

Background:

• Human mitochondrial DNA (mtDNA) harbors guanine-rich regions capable of forming G-quadruplex structures (G4s).
• These G4 structures are implicated in mtDNA replication and stability.
• The role of mitochondrial proteins in recognizing these G4s remains largely unexplored.

Purpose of the Study:

• To investigate the interaction between mitochondrial transcription factor A (TFAM) and G-quadruplex structures.
• To determine if TFAM, a key mtDNA binding protein, recognizes G4s within the mitochondria.

Main Methods:

• Biochemical characterization of TFAM binding to various DNA and RNA G4 structures.
• Pull-down experiments using G4-DNA from mtDNA conserved sequence block II (CSBII) in mitochondrial extracts.
• Analysis of TFAM binding affinity and specificity to G4s versus double-stranded DNA (dsDNA).

Main Results:

• TFAM exhibits versatile binding to both DNA and RNA G4 structures with an affinity comparable to double-stranded DNA.
• Endogenous TFAM recognition of G4s was confirmed in mitochondrial extracts.
• TFAM binding to G4s is dependent on the G-quartet core and single-stranded overhangs, with a distinct binding mode from B-DNA.
• G4 binding induces TFAM multimerization.

Conclusions:

• TFAM possesses a significant and versatile G4-binding capability.
• These findings suggest a functional role for TFAM in recognizing and potentially regulating G4 structures within mitochondria.
• This interaction opens new avenues for understanding mtDNA regulation and stability.