Cortez Lab

Oligomerization of DNA replication regulatory protein RADX is essential to maintain replication fork stability

AUTHORS

ABSTRACT

Genome integrity requires complete and accurate DNA replication every cell division cycle. Replication stress poses obstacles to this process that must be overcome to prevent replication fork collapse. An important regulator of replication fork stability is the RAD51 protein, which promotes replication fork reversal and protects nascent DNA strands from nuclease-mediated degradation. Many regulatory proteins control these RAD51 activities, including RADX, which binds both single-stranded DNA and RAD51 at replication forks to ensure that fork reversal is confined to stalled forks. Many single-stranded DNA binding proteins function as hetero- or homo-oligomers. In this study we addressed whether this is also the case for RADX. Using biochemical and genetic approaches we found that RADX acts as a homo-oligomer to control replication fork stability. RADX oligomerizes using at least two different interaction surfaces, including one mapped to a C-terminal region. We demonstrate that mutations in this region prevent oligomerization and prevent RADX function in cells, and that addition of a heterologous dimerization domain to the oligomerization mutants restored their ability to regulate replication. Taken together, our results demonstrate that like many single-stranded DNA binding proteins, oligomerization is essential for RADX-mediated regulation of genome stability.