Ubiquitin Receptor-Induced Proximity is Sufficient for Ubiquitin-Independent Targeted Protein Degradation via the 26S Proteasome

Park, S. H.; Jang, Y.; Kim, E.; Jeong, D.; Byun, I.; Kim, J.; Yang, J.; Lee, C. H.; Han, D.; Lee, M. J.

doi:10.1101/2025.08.18.670774

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bioRxiv · 10.1101/2025.08.18.670774

Ubiquitin Receptor-Induced Proximity is Sufficient for Ubiquitin-Independent Targeted Protein Degradation via the 26S Proteasome

Park, S. H.·Jang, Y.·Kim, E.·Jeong, D.·Byun, I.·Kim, J.·Yang, J.·Lee, C. H.·Han, D.·Lee, M. J.

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Abstract

The 26S proteasome engages with ubiquitinated substrates primarily through its constituent ubiquitin (Ub) receptors, which initiates a cascade of proteolytic processes. Leveraging this recognition mechanism, we developed a targeted protein degradation (TPD) strategy that recruits substrates directly to the proteasome, thereby bypassing the ubiquitination step. Our proteasome-targeting chimera, Protea-Tac, is a heterobifunctional protein degrader composed of a Ub receptor and an intracellular antibody. This chimera integrates into 26S proteasomes without altering their functional integrity. Localization of target proteins, including c-Fos, BRD4, Flag-TDP43, HA-tau, and GFP-ODC, to the proteasome via Protea-Tac with cognate antibodies resulted in their induced degradation. We demonstrated that this platform is 1) modular, allowing facile switching between targets; 2) Ub-independent; and 3) highly target-specific. Protea-Tac exhibited in vivo anti-tumor efficacy, degrading c-Fos and substantially delaying tumor growth. Overall, these findings identify Protea-Tac as a distinct TPD modality capable of directly degrading intracellular proteins via engineered 26S proteasomes. TeaserProtea-Tac is a heterobifunctional protein degrader that enables Ub-independent TPD, exhibits high specificity and modularity, and demonstrates in vivo applicability.

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Park, S. H., Jang, Y., Kim, E., Jeong, D., Byun, I., Kim, J., Yang, J., Lee, C. H., Han, D., Lee, M. J.. 2025-08-19. Ubiquitin Receptor-Induced Proximity is Sufficient for Ubiquitin-Independent Targeted Protein Degradation via the 26S Proteasome. https://doi.org/10.1101/2025.08.18.670774

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