National Institutes of Health/National Institute Of Allergy and Infectious Diseases (NIH/NIAID)
R35 GM118089, P01 CA092584
米国
引用
ジャーナル: bioRxiv / 年: 2023 タイトル: Structure of RADX and mechanism for regulation of RAD51 nucleofilaments. 著者: Swati Balakrishnan / Madison Adolph / Miaw-Sheue Tsai / Kaitlyn Gallagher / David Cortez / Walter J Chazin / 要旨: 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 ...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.