Minute amounts of helicase-deficient truncated RECQL4 are sufficient for DNA replication

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• RECQL4 is a RecQ family helicase crucial for DNA replication and genome stability.
• RECQL4 mutations lead to severe human genetic disorders, but its precise functions remain unclear, especially its ATP-dependent helicase activity.

Purpose of the Study:

• To further elucidate the functions of RECQL4, particularly its role in DNA replication.
• To identify genetic modifiers that can rescue RECQL4 deficiency.

Main Methods:

• A genome-wide forward genetic screen was conducted using a murine model with patient-like RECQL4 mutations.
• CRISPR-Cas9 technology was employed for gene editing and recombination.
• Cellular proliferation and DNA replication assays were performed on RECQL4-deficient cells.

Main Results:

• Loss of KLHDC3, a component of the Cullin-RING ligase E3 complex, was identified as a significant rescue allele.
• KLHDC3 loss restored proliferation and replication in RECQL4-deficient cells.
• This rescue was mediated by stabilizing a truncated RECQL4 fragment (N-terminal 480 amino acids) lacking helicase and C-terminal domains.

Conclusions:

• A minimal RECQL4 fragment, devoid of ATPase activity, is sufficient to support DNA replication and cell viability.
• RECQL4 acts as an essential, non-redundant regulator of DNA replication and cell viability.
• The ATP-dependent helicase activity of RECQL4 is not required for its fundamental role in DNA replication.