Physical interactions between MCM and Rad51 facilitate replication fork lesion bypass and ssDNA gap filling by non-recombinogenic functions

The minichromosome maintenance (MCM) helicase physically interacts with the recombination proteins Rad51 and Rad52 from yeast to human cells. We show, in Saccharomyces cerevisiae, that these interactions occur within a nuclease-insoluble scaffold enriched in replication/repair factors. Rad51 accumulates in a MCM- and DNA-binding-independent manner and interacts with MCM helicases located outside of the replication origins and forks. MCM, Rad51, and Rad52 accumulate in this scaffold in G1 and are released during the S phase. In the presence of replication-blocking lesions, Cdc7 prevents their release from the scaffold, thus maintaining the interactions. We identify a rad51 mutant that is impaired in its ability to bind to MCM but not to the scaffold. This mutant is proficient in recombination but partially defective in single-stranded DNA (ssDNA) gap filling and replication fork progression through damaged DNA. Therefore, cells accumulate MCM/Rad51/Rad52 complexes at specific nuclear scaffolds in G1 to assist stressed forks through non-recombinogenic functions. [Display omitted] •Rad51 and Rad52 interact with MCM in a nuclease-insoluble nucleoprotein scaffold•MCM/Rad51/Rad52 accumulation is regulated by cell cycle and replicative DNA damage•Cdc7 prevents Rad51/Rad52 release from the scaffold under replicative DNA damage•MCM/Rad51 promotes MMS-induced gap filling and fork progression by non-HR processes Cabello-Lobato et al. find that MCM interacts dynamically with Rad51 and Rad52 within a nuclease-insoluble nucleoprotein scaffold. These interactions are established in G1 and maintained in the S phase by Cdc7 in the presence of replication-blocking lesions to assist stressed forks through non-recombinogenic functions.