# DEFINING THE FUNCTION OF PROTEASOMAL DEUBIQUITINASES

> **NIH NIH R01** · UNIVERSITY OF MASSACHUSETTS AMHERST · 2021 · $362,262

## Abstract

Project Summary
The 26S proteasome is a massive, intricately regulated ATP-dependent protease that is responsible for the
degradation of most cellular proteins. Failure of the proteasome to precisely regulate protein levels is a
hallmark of many cancers and neurodegenerative diseases. Targeting proteins to the proteasome requires
covalent modification with a polymeric (Ub) chain. Thus, it is perplexing that the proteasome actually houses
enzymes (deubiquitinases/DUBs) responsible for removing Ub chains. While it has become clear that the
intrinsic DUB, RPN11, promotes degrades by preventing premature deubiquitination of proteins not yet
engaged with the proteasome, the roles of other proteasomal DUBs, e.g., UCH37/UCHL5, are poorly
understood. In preliminary studies, we discovered that proteasome-bound UCH37 acts as a chain editor by
removing branch points. This application proposes to elucidate how UCH37 selects branched Ub chains for
editing, how this activity is integrated into the entire process of proteasomal degradation, and how it impacts
the turnover of cellular proteins. In Aim 1, we will investigate the role of UCH37-mediated chain debranching
during proteasomal degradation using distinct, purified human proteasome complexes and fluorescent,
polyubiquitinated substrates. In Aim 2, we propose to identify cellular targets of proteasome-bound UCH37
using an innovative combination of quantitative proteomics, in-cell proximity labeling, and Ub middle-down
mass spectrometry. In Aim 3, we focus on understanding the molecular basis of UCH37's specificity toward
branched chains. Finally, in Aim 4, we will develop novel cyclic peptide inhibitors of UCH37 to facilitate efforts
to dissect its function in any biological paradigm. The knowledge gained from this research will shed light on
fundamental aspects of the ubiquitin proteasome system and pave the way for the development of new
therapeutics that regulate proteasome function.

## Key facts

- **NIH application ID:** 10221698
- **Project number:** 5R01GM110543-09
- **Recipient organization:** UNIVERSITY OF MASSACHUSETTS AMHERST
- **Principal Investigator:** ERIC Robert STRIETER
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $362,262
- **Award type:** 5
- **Project period:** 2014-08-01 → 2023-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10221698

## Citation

> US National Institutes of Health, RePORTER application 10221698, DEFINING THE FUNCTION OF PROTEASOMAL DEUBIQUITINASES (5R01GM110543-09). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10221698. Licensed CC0.

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