CUL4A and xeroderma pigmentosum: Despite such a negative effect exerted by the GFP tag on the CUL4A machinery, this construct complements the overt hypersensitivity of XP-C cells to killing by UV radiation [47] and, in our study, provides a helpful tool to demonstrate that it is the ubiquitylation of XPC itself that fine-tunes the nucleosome partitioning of this repair initiator.