The xeroderma pigmentosum group C protein complex and ultraviolet-damaged DNA-binding protein: functional assays for damage recognition factors involved in global genome repair.

In mammalian nucleotide excision repair (NER) operating throughout the genome, DNA lesions are recognized by protein factors that specifically bind to the damaged sites. Such damage recognition factors involve the xeroderma pigmentosum group C (XPC) protein complex and ultraviolet (UV)-damaged DNA-binding protein (UV-DDB). To assess specific DNA-binding activities of these factors, it is useful to take advantage of biochemical assays using DNA substrates that contain a defined lesion and/or artificial structure in a site-specific manner. In addition, it has been shown that both XPC and UV-DDB are ubiquitylated in response to UV irradiation of cells. This ubiquitylation is mediated by ubiquitin ligase associated with UV-DDB and is important for the NER process of UV-induced lesions. Methods for detecting the UV-DDB-dependent ubiquitylation in vivo and in vitro are also described.