Replication blocking lesions present a unique substrate for homologous recombination

EMBO J. 2007 Jul 25;26(14):3384-96. doi: 10.1038/sj.emboj.7601766. Epub 2007 Jul 5.


Homologous recombination (HR) plays a critical role in the restart of blocked replication forks, but how this is achieved remains poorly understood. We show that mutants in the single Rad51 paralog in Caenorhabditis elegans, rfs-1, permit discrimination between HR substrates generated at DNA double-strand breaks (DSBs), or following replication fork collapse from HR substrates assembled at replication fork barriers (RFBs). Unexpectedly, RFS-1 is dispensable for RAD-51 recruitment to meiotic and ionizing radiation (IR)-induced DSBs and following replication fork collapse, yet, is essential for RAD-51 recruitment to RFBs formed by DNA crosslinking agents and other replication blocking lesions. Deletion of rfs-1 also suppresses the accumulation of toxic HR intermediates in him-6; top-3 mutants and accelerates deletion formation at presumed endogenous RFBs formed by poly G/C tracts in the absence of DOG-1. These data suggest that RFS-1 is not a general mediator of HR-dependent DSB repair, but acts specifically to promote HR at RFBs. HR substrates generated at conventional DSBs or following replication fork collapse are therefore intrinsically different from those produced during normal repair of blocked replication forks.

MeSH terms

  • Animals
  • Caenorhabditis elegans / cytology
  • Caenorhabditis elegans / genetics*
  • Caenorhabditis elegans / radiation effects
  • Caenorhabditis elegans Proteins / metabolism
  • Crossing Over, Genetic / radiation effects
  • DNA Breaks, Double-Stranded / radiation effects
  • DNA Damage*
  • DNA Repair / radiation effects
  • DNA Replication* / radiation effects
  • Gene Deletion
  • Meiosis / radiation effects
  • Mitosis / radiation effects
  • Poly C
  • Poly G
  • Protein Binding / radiation effects
  • Rad51 Recombinase / metabolism
  • Recombination, Genetic* / radiation effects
  • Substrate Specificity / radiation effects
  • Suppression, Genetic / radiation effects
  • Ultraviolet Rays


  • Caenorhabditis elegans Proteins
  • Poly G
  • poly G-poly C
  • Poly C
  • Rad51 Recombinase