The differences between ICL repair during and outside of S phase

•Interstrand crosslinks are repaired by distinct pathways during and outside of S phase.•ICL repair outside of S phase is critical for cellular homeostasis, particularly in postmitotic or rarely dividing cells. DNA interstrand crosslinks (ICLs) are complex lesions that block essential DNA transactions including DNA replication, recombination, and RNA transcription. Naturally occurring ICLs are rare, yet these lesions are the major cause of toxicity following treatment with several classes of crosslinking cancer chemotherapeutic drugs. ICLs are repaired during and outside of S phase by pathways with overlapping as well as distinct features. Here, we discuss some recent insights into the mechanisms of replication-dependent and replication-independent repair of ICLs with special emphasis on the differences between these repair pathways.