Structural elements required for the efficient loading and activation of HELB on RPA-coated single-stranded DNA

Area of Science:

• Molecular Biology
• Biochemistry
• Genetics

Background:

• HELB (Helicase Like) is a human helicase essential for DNA repair and replication.
• HELB interacts with RPA (Replication Protein A), a key single-stranded DNA binding protein.
• HELB's function involves ATP-dependent translocation along ssDNA, displacing RPA and forming ssDNA loops.

Purpose of the Study:

• To investigate the role of HELB-specific structural elements in its interaction with RPA-coated DNA.
• To elucidate the mechanisms by which HELB facilitates RPA displacement and ssDNA loop formation.

Main Methods:

• Structural analysis of HELB, focusing on its N-terminal OB-fold and RecA-like domains.
• Biochemical assays to assess RPA binding and displacement in the presence of ssDNA.
• Functional studies to evaluate the importance of specific motifs for HELB activity.

Main Results:

• A predicted OB-fold in HELB's N-terminus is crucial for both ssDNA loop extrusion and RPA displacement.
• A HELB-specific motif in the RecA-like domains is essential for binding RPA in solution.
• This motif becomes dispensable for RPA displacement once HELB is bound to ssDNA.

Conclusions:

• HELB utilizes distinct structural elements for RPA interaction and DNA processing.
• A model is proposed where the OB-fold and RecA-like domains cooperate to recruit and activate HELB at RPA-ssDNA filaments.
• These findings provide insights into the mechanism of RPA displacement during DNA repair and replication.