FA cells are deficient in fork protection, which leads to SLFN11-mediated DNA damage and death. During DNA synthesis (S-phase) in wild-type cells, DNA replication forks can be stalled by ICLs or other DNA damage (yellow lightning bolt). In wild-type cells, fork protection is activated by the Fanconi pathway. This includes 2 key steps: formation of a FANCD2 DNA clamp adjacent to the damaged DNA that activates repair, and BRCA-RAD51–mediated recombination that restarts DNA replication. In FA cells, this fork protection is absent. Instead, aberrant RAD51 promotes nuclease attack by DNA2 and MRE11 nucleases. SLFN11 is normally regulated as part of fork protection, but it activates the RAD51-DNA2-MRE11 destruction of forks in Fanconi cells and triggers their G₂/M arrest and/or death. Consequently, SLFN11 deletion in Fanconi cells restores normal mitoses and wild-type levels of viability after DNA damage. Figure created with Biorender.com.