The protein shuffle. Sequential interactions among components of the human nucleotide excision repair pathway

Xeroderma pigmentosum (XP) is an inherited disease in which cells from patients exhibit defects in nucleotide excision repair (NER). XP proteins A-G are crucial in the processes of DNA damage recognition and incision, and patients with XP can carry mutations in any of the genes that specify these proteins. In mammalian cells, NER is a dynamic process in which a variety of proteins interact with one another, via modular domains, to carry out their functions. XP proteins are key players in several steps of the NER process, including DNA strand discrimination (XPA, in complex with replication protein A), repair complex formation (XPC, in complex with hHR23B; XPF, in complex with ERCC1) and repair factor recruitment (transcription factor IIH, in complex with XPG). Through these protein-protein interactions, various types of bulky DNA adducts can be recognized and repaired. Communication between the NER system and other cellular pathways is also achieved by selected binding of the various structural domains. Here, we summarize recent studies on the domain structures of human NER components and the regulatory networks that utilize these proteins. Data provided by these studies have helped to illuminate the complex molecular interactions among NER factors in the context of DNA repair.