Download MendeleyStructural insights into the ubiquitin-independent midnolin-proteasome pathway.
Peddada, N., Zhong, X., Yin, Y., Lazaro, D.R., Wang, J., Lyon, S., Choi, J.H., Bai, X.C., Moresco, E.M.Y., Beutler, B.(2025) Proc Natl Acad Sci U S A 122: e2505345122-e2505345122
- PubMed: 40339123
- DOI: https://doi.org/10.1073/pnas.2505345122
- Primary Citation of Related Structures:
9NKF, 9NKG, 9NKI, 9NKJ - PubMed Abstract:
The protein midnolin (MIDN) augments proteasome activity in lymphocytes and dramatically facilitates the survival and proliferation of B-lymphoid malignancies. MIDN binds both to proteasomes and to substrates, but the mode of interaction with the proteasome is unknown, and the mechanism by which MIDN facilitates substrate degradation in a ubiquitin-independent manner is incompletely understood. Here, we present cryoelectron microscopy (cryo-EM) structures of the substrate-engaged, MIDN-bound human proteasome in two conformational states. MIDN induces proteasome conformations similarly to ubiquitinated substrates by using its ubiquitin-like domain to bind to the deubiquitinase RPN11 (PSMD14). By simultaneously binding to RPN1 (PSMD2) with its C-terminal α-helix, MIDN positions its substrate-carrying Catch domain above the proteasome ATPase channel through which substrates are translocated before degradation. Our findings suggest that both ubiquitin-like domain and C-terminal α-helix must bind to the proteasome for MIDN to stimulate proteasome activity.
- Center for the Genetics of Host Defense, University of Texas Southwestern Medical Center, Dallas, TX 75390.
Organizational Affiliation:
