In such a situation, short ubiquitin chains synthesised by TRAIP on CMGs promote the recruitment of NEIL3 glycosylase and unhooking of the ICL, whilst longer ubiquitin chains are required for CMG unloading by p97 segregase, allowing access for endonucleases and Fanconi anaemia pathway proteins that perform ICL repair13,16,17. The gene discussed is TRAIP; the disease is Fanconi anemia.