Structural basis for multifunctional roles of human Ints3 C-terminal domain

Area of Science:

• Molecular biology
• Structural biology
• Genetics

Background:

• DNA repair is crucial for genome stability.
• The Integrator complex, including Ints3, SSB1, and SSBIP1, is vital for double-strand break repair and ATM signaling.
• The function of the Ints3 C-terminal domain in this complex was previously unknown.

Purpose of the Study:

• To elucidate the molecular structure and function of the Ints3 C-terminal domain.
• To understand its role in DNA repair and protein complex interactions.

Main Methods:

• X-ray crystallography to determine the Ints3 C-terminal domain structure.
• Structure-based mutation analysis.
• In vitro experiments with HEK 293T cells.

Main Results:

• The Ints3 C-terminal domain adopts a HEAT-repeat superhelical fold and forms a stable dimer.
• The dimer binds single-stranded RNA/DNA (ssRNA/ssDNA) and Integrator complex subunit 6 (Ints6).
• Ints6 binding is essential for maintaining SSB1 protein levels.

Conclusions:

• The study reveals the structural basis of the Ints3 C-terminal module's multifunctionality.
• A novel mode of ssRNA/ssDNA recognition by a helical repeat protein is proposed.
• The findings provide insights into DNA repair mechanisms and Integrator complex regulation.