Structural and functional insights into the Rad51 paralog complexes Shu and Rad55-Rad57 in association with Rad51 in homologous recombination

ABSTRACT: RAD51 filaments are essential to repair DNA double-strand breaks (DSB) and single-strand DNA (ssDNA) gaps. RAD51 filament formation depends on RAD51 paralogs, but their functions remain unclear. Here, we combined structural modeling and functional analyses to characterize how the yeast Rad51 paralog complexes Shu and Rad55-Rad57 interact with Rad51 filaments. We validated the AlphaFold model that integrates Shu, Rad55-Rad57 and Rad51 using targeted mutagenesis and protein interaction assays. Structure-guided mutations showed the critical role of Rad55-Rad57 complex integrity. Disrupting Csm2-Rad55 interaction demonstrated that Shu function requires its association with Rad55-Rad57. Shu was essential for ssDNA gap, but not DSB repair. Lastly, the Rad57-Rad51 interaction relies on several independent, non-essential contacts. Their mutation highlighted Rad55-Rad57 essential role in Rad51 filament formation in cooperation with Rad52. These findings suggest that Rad55-Rad57 caps the Rad51 filament 5′-end to promote its formation, whereas the Shu-Rad55-Rad57 megacomplex anchors and stabilizes filaments on ssDNA gaps.

INSTRUMENT(S):

ORGANISM(S): Saccharomyces Cerevisiae (baker's Yeast)

SUBMITTER: Eric Coic  

LAB HEAD: Eric Coic

PROVIDER: PXD086326 | Pride | 2026-10-27

REPOSITORIES: Pride