8U5Y

human RADX trimer bound to ssDNA

This is a non-PDB format compatible entry.

Summary for 8U5Y

• Entry DOI: 10.2210/pdb8u5y/pdb
• EMDB information: 41939
• Descriptor: RPA-related protein RADX, DNA (25-MER) (2 entities in total)
• Functional Keywords: oligomer ob-fold, rad51 regulator, dna binding protein, dna binding protein-dna complex, dna binding protein/dna
• Biological source: Homo sapiens (human); More
• Total number of polymer chains: 4
• Total formula weight: 300600.15

Authors

Balakrishnan, S.,Chazin, W.J. (deposition date: 2023-09-13, release date: 2023-10-11, Last modification date: 2023-10-18)

Primary citation

Balakrishnan, S.,Adolph, M.,Tsai, M.S.,Gallagher, K.,Cortez, D.,Chazin, W.J.
Structure of RADX and mechanism for regulation of RAD51 nucleofilaments.
Biorxiv, 2023

PubMed Abstract: Replication fork reversal is a fundamental process required for resolution of encounters with DNA damage. A key step in the stabilization and eventual resolution of reversed forks is formation of RAD51 nucleoprotein filaments on exposed ssDNA. To avoid genome instability, RAD51 filaments are tightly controlled by a variety of positive and negative regulators. RADX is a recently discovered negative regulator that binds tightly to ssDNA, directly interacts with RAD51, and regulates replication fork reversal and stabilization in a context-dependent manner. Here we present a structure-based investigation of RADX's mechanism of action. Mass photometry experiments showed that RADX forms multiple oligomeric states in a concentration dependent manner, with a predominance of trimers in the presence of ssDNA. The structure of RADX, which has no structurally characterized orthologs, was determined by cryo-electron microscopy (EM) from maps in the 2-3 Å range. The structure reveals the molecular basis for RADX oligomerization and binding of ssDNA binding. The binding of RADX to RAD51 filaments was imaged by negative stain EM, which showed a RADX oligomer at the end of filaments. Based on these results, we propose a model in which RADX functions by capping and restricting the growing end of RAD51 filaments.

PubMed: 37786681
DOI: 10.1101/2023.09.19.558089

Experimental method

ELECTRON MICROSCOPY (3.01 Å)