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Cited by 21Ubiquitin and proteasome pathwaysProtein Degradation and InhibitorsHeat shock proteins research

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NUB1 traps unfolded FAT10 for ubiquitin-independent degradation by the 26S proteasome

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Arkinson, Connor, Dong, Ken C., Gee, Christine L., Costello, Shawn M., Soe, Aimee Chi, Hura, Greg L., Marqusee, Susan, Martin, Andreas·2025·Nature Structural & Molecular Biology
DOI 10.1038/s41594-025-01527-3PMC PMC12285911

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Abstract

The ubiquitin-like modifier FAT10 targets hundreds of proteins in the mammalian immune system to the 26S proteasome for degradation. This degradation pathway requires the cofactor NUB1, yet the underlying mechanisms remain unknown. Here, we reconstituted a minimal in vitro system with human components and revealed that NUB1 uses the intrinsic instability of FAT10 to trap its N-terminal ubiquitin-like domain in an unfolded state and deliver it to the 26S proteasome for engagement, allowing the degradation of FAT10-ylated substrates in a ubiquitin-independent and p97-independent manner. Using hydrogen–deuterium exchange, structural modeling and site-directed mutagenesis, we identified the formation of an intricate complex with FAT10 that activates NUB1 for docking to the 26S proteasome, and our cryo-EM studies visualized the highly dynamic NUB1 complex bound to the proteasomal Rpn1 subunit during FAT10 delivery and the early stages of ATP-dependent degradation. These findings identified a previously unknown mode of cofactor-mediated, ubiquitin-independent substrate delivery to the 26S proteasome that relies on trapping partially unfolded states for engagement by the proteasomal ATPase motor.

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Metadata

Authors
Arkinson, C., Dong, K. C., Gee, C. L., Costello, S. M., Soe, A. C., Hura, G. L., Marqusee, S., & Martin, A.
Affiliations
  • QB3 (US)
  • Howard Hughes Medical Institute (US)
  • University of California, Berkeley (US)
  • Lawrence Berkeley National Laboratory (US)
Corresponding author
Martin, Andreas
ORCID
Venue
Nature Structural & Molecular Biology
Publisher
Springer Science and Business Media LLC
Published
2025-04-11
Volume
32
Issue
9
Pages
1752-1765
ISSN
  • 1545-9985 (ISSN-L)
  • 1545-9993
DOI
10.1038/s41594-025-01527-3
PMC
PMC12285911
OpenAlex
W4409371304
Cited by
21
References
3
Citations by year
2026: 11 · 2025: 8
FWCI
5.63
Type
journal article
Language
en
Open access
Licence
Locations
  • Nature Structural & Molecular Biology (publishedVersion, cc-by)
  • bioRxiv (Cold Spring Harbor Laboratory) (acceptedVersion, cc-by-nc-nd)
  • PubMed (publishedVersion)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed Central (submittedVersion, cc-by-nc-nd)
  • eScholarship (California Digital Library) (submittedVersion, cc-by)
Funders
National Institute of General Medical Sciences (R01GM094497, R35GM149319, P30GM124169)
Topics
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Ubiquitin and proteasome pathways
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Protein Degradation and Inhibitors
  • Life Sciences › Biochemistry, Genetics and Molecular Biology › Molecular Biology › Heat shock proteins research
Keywords
FAT10, NUB1, ubiquitin-independent degradation, 26S proteasome, ubiquitin-like proteins, protein unfolding, substrate supply, RPN1, immune system proteins

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