FAT10 and NUB1L bind to the VWA domain of Rpn10 and Rpn1 to enable proteasome-mediated proteolysis.

FAT10 is the only ubiquitin-like modifier that can target proteins for degradation by the proteasome in a ubiquitin-independent manner. The degradation of FAT10-linked proteins by the proteasome is strongly accelerated by the ubiquitin-like-ubiquitin-associated protein NEDD8 ultimate buster-1 long (NUB1L). Here we show how FAT10 and NUB1L dock with the 26S proteasome to initiate proteolysis. We identify the 26S proteasome subunit hRpn10/S5a as the receptor for FAT10, whereas NUB1L can bind to both Rpn10 and Rpn1/S2. Unexpectedly, FAT10 and NUB1L both interact with hRpn10 via the VWA domain. FAT10 degradation in yeast shows that human Rpn10 can functionally reconstitute Rpn10-deficient yeast and that the VWA domain of hRpn10 suffices to enable FAT10 degradation. Depletion of hRpn10 causes an accumulation of FAT10-conjugates also in human cells. In conclusion, we identify the VWA domain of hRpn10 as a receptor for ubiquitin-like proteins within the 26S proteasome and elucidate how FAT10 mediates efficient proteolysis by the proteasome.