In particular, they possess an N-terminal ubiquitin-like domain (UBL), a central ubiquitin-associated domain (UBA1), followed by a RAD4/XPC (xeroderma pigmentosum group C) binding domain (RBD/XPCB) and a C-terminal ubiquitin-associated domain (UBA2). Here, XPC is linked to xeroderma pigmentosum group C.