The Rad23 family includes the yeast nucleotide excision repair (NER) proteins, Rad23p (in Saccharomyces cerevisiae) and Rhp23p (in Schizosaccharomyces pombe), their mammalian orthologs HR23A and HR23B, and putative DNA repair proteins from plants. Rad23 proteins play dual roles in DNA repair as well as in proteosomal degradation. They have affinity for both the proteasome and ubiquitinylated proteins and participate in translocating polyubiquitinated proteins to the proteasome. Rad23 proteins carry a ubiquitin-like (UBL) and two ubiquitin-associated (UBA) domains, as well as a xeroderma pigmentosum group C (XPC) protein-binding domain. UBL domain is responsible for the binding to proteasome. UBA domains are important for binding of ubiquitin (Ub) or multi-ubiquitinated substrates which suggests Rad23 proteins might be involved in certain pathways of ubiquitin metabolism. Both UBL domain and XPC-binding domain are necessary for efficient NER function of Rad23 proteins. This model corresponds to the UBA2 domain.
Jiyao W et al.(2023). "The conserved domain database in 2023.",