DNA2 and MSH2 activity collectively mediate chemically stabilized G4 for efficient telomere replication

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• G-quadruplexes (G4s) are stable DNA structures in mammalian cells.
• Their timely resolution is hypothesized to be essential for DNA replication fidelity.
• The DNA2-mediated G4 removal pathway's biological significance remains largely unknown.

Purpose of the Study:

• To investigate the biological role of the DNA2-mediated G4 removal pathway.
• To elucidate the regulatory mechanism of G4 resolution.
• To understand the impact of G4 stabilizers on telomere replication.

Main Methods:

• Single molecular analysis of replicating DNA (SMARD) technology.
• Assessing G4 accumulation and replication fork stalling upon DNA2 inhibition.
• Investigating the interaction between MutSα (MSH2-MSH6) and G4s.
• Evaluating the effects of G4-stabilizing compounds on DNA2 and helicase activity.

Main Results:

• DNA2 deficiency or inhibition causes significant G4 accumulation and telomere replication fork stalling.
• MutSα (MSH2-MSH6) binds G4s and promotes their resolution via DNA2.
• MSH2 deficiency mirrors DNA2 deficiency effects, leading to G4 accumulation and defective telomere replication.
• G4 stabilizers inhibit helicase-mediated unwinding but not DNA2-mediated cleavage, impairing telomere replication and causing instability, particularly in DNA2- or MSH2-deficient cells.

Conclusions:

• DNA2 and MutSα (MSH2-MSH6) are critical for resolving G-quadruplexes during DNA replication.
• This pathway is essential for maintaining telomere replication fidelity and stability.
• G4 stabilizers pose a risk to telomere integrity, especially in cells with compromised G4 resolution pathways.