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UBA2 domain of UV excision repair protein RAD23 homolog B (HR23B) found in vertebrates HR23B, also called xeroderma pigmentosum group C (XPC) repair-complementing complex 58 kDa protein (p58), is tightly complexed with XPC protein to form the XPC-HR23B complex. Although it displays a high affinity for both single- and double-stranded DNA, the XPC-HR23B complex functions as a global genome repair (GGR)-specific repair factor that is specifically involved in global genome but not transcription-coupled nucleotide excision repair (NER). HR23B also interacts specifically with S5a subunit of the human 26 S proteasome, and plays an important role in shuttling ubiquitinated cargo proteins to the proteasome. HR23B contains an N-terminal ubiquitin-like (UBL) domain that binds proteasomes and two C-terminal ubiquitin-associated (UBA) domains that bind ubiquitin or multi-ubiquitinated substrates. In addition, it has a XPC protein-binding domain that might be necessary for its efficient NER function. This model corresponds to the UBA2 domain.
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