%0 Journal Article %J Nature Structural & Molecular Biology %D 2022 %T Mechanism of client selection by the protein quality-control factor UBE2O %A Yip, Matthew C. J. %A Sedor, Samantha F. %A Shao, Sichen %X The E2/E3 enzyme UBE2O ubiquitylates diverse clients to mediate important processes, including targeting unassembled `orphan' proteins for quality control and clearing ribosomes during erythropoiesis. How quality-control factors, such as UBE2O, select clients on the basis of heterogeneous features is largely unknown. Here, we show that UBE2O client selection is regulated by ubiquitin binding and a cofactor, NAP1L1. Attaching a single ubiquitin onto a client enhances UBE2O binding and multi-mono-ubiquitylation. UBE2O also repurposes the histone chaperone NAP1L1 as an adapter to recruit a subset of clients. Cryo-EM structures of human UBE2O in complex with NAP1L1 reveal a malleable client recruitment interface that is autoinhibited by the intrinsically reactive UBC domain. Adding a ubiquitylated client identifies a distinct ubiquitin-binding SH3-like domain required for client selection. Our findings reveal how multivalency and a feed-forward mechanism drive the selection of protein quality-control clients. %B Nature Structural & Molecular Biology %8 Aug %G eng %U https://doi.org/10.1038/s41594-022-00807-6 %R 10.1038/s41594-022-00807-6