# Degradation of Short Lived Regulatory Proteins

> **NIH NIH R01** · YALE UNIVERSITY · 2020 · $387,779

## Abstract

Project Summary
Eukaryotic cells have a highly conserved enzymatic system for ligating ubiquitin (Ub) to proteins. Frequently, the
modification leads to degradation of the targeted protein, usually by the proteasome. Ub-protein conjugates
are highly dynamic, being rapidly reversed by proteases called deubiquitylating enzymes (DUBs). Ub has
many crucial roles, including important contributions to human biology. Substrates include naturally short-lived
regulators and aberrant “protein quality control” (PQC) substrates. Many human disorders, including
neurodegenerative diseases, diabetes, and different cancers, are associated with abnormalities in Ub-
dependent proteolysis. The Ub-proteasome system presents many drug targets for disease treatment.
In this renewal, the PI proposes to extend studies on Ub-protein modification and degradation in several regulatory
systems. One focus is on endoplasmic reticulum (ER)-associated degradation (ERAD) and nuclear
envelope-associated degradation (NEAD). The proposed research will concentrate on the yeast Saccharomyces
cerevisiae because of its experimental advantages and the strong conservation of the Ub system. Work from
the PI previously identified an ERAD/NEAD Ub ligase called Doa10. There are still many outstanding questions
regarding its mechanism and function. A new area of regulatory proteolysis initiated by the PI is degradation of Sts1,
an essential protein that regulates both PQC at the ribosome and proteasome trafficking between the cytoplasm and
nucleus. Degradation of Sts1 is intimately linked to its functional state. A final, also new research area addresses
Ub system enzymes from obligate intracellular bacteria that infect humans and other species. One focus is on a
DUB from Orientia tsutsugamushi, the causative agent of scrub typhus, a highly lethal disease. Initial analysis
revealed the DUB has many unusual properties, including very tight binding to both Ub and clathrin adaptor
proteins.
The overarching goal of the proposal is to uncover the key biochemical, structural and cell biological features
of these regulatory systems. The following Aims are proposed: (1) Investigate mechanistic features of the ER/NE-
localized Doa10 Ub ligase, including substrate recognition and the role of Doa10 as a possible membrane-protein
extraction factor, and conduct structural studies of the ligase; (2) Determine how the short-lived S. cerevisiae
Sts1 karyopherin -binding protein is degraded and how it regulates nuclear transport, proteasome
dynamics, and compartment- specific proteolysis; and (3) Examine how a Ub system enzyme expressed by
the O. tsutsugamushi intracellular pathogen interferes with membrane trafficking.

## Key facts

- **NIH application ID:** 9926896
- **Project number:** 5R01GM046904-30
- **Recipient organization:** YALE UNIVERSITY
- **Principal Investigator:** Mark W Hochstrasser
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $387,779
- **Award type:** 5
- **Project period:** 1992-02-01 → 2021-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9926896

## Citation

> US National Institutes of Health, RePORTER application 9926896, Degradation of Short Lived Regulatory Proteins (5R01GM046904-30). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/9926896. Licensed CC0.

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