Disassembly of Lys11 and mixed linkage polyubiquitin conjugates provides insights into function of proteasomal deubiquitinases Rpn11 and Ubp6

Abstract

Background: Deconjugation of polyubiquitin is an essential step in preparing substrates for proteolysis by the 26S proteasome. Results: Proteasome-associated DUBs, Rpn11 and Ubp6, process long Lys11- or Lys63-linked polyUb more efficiently than Lys48 linkages. Conclusion: 26S proteasomes can completely disassemble a mixed/branched polyUb conjugate. Significance: These observations call into question what constitutes an efficient signal for proteasome targeting versus proteolysis.