SLX4IP acts in parallel to FANCM to limit BLM-dependent replication stress at ALT telomeres.

Alternative Lengthening of Telomeres (ALT) is a telomerase-independent telomere maintenance mechanism that enables cancer cells to gain unlimited replicative capacity. ALT relies on recombination-mediated telomere elongation and is promoted by telomeric replication stress. However, ALT requires strict regulation, as excessive replication stress or recombination are cytotoxic.