# Structural Biology of the Ubiquitin Conjugation System

> **NIH NIH R01** · UNIVERSITY OF TEXAS HLTH SCIENCE CENTER · 2020 · $313,680

## Abstract

Project Summary
Posttranslational modification of proteins by ubiquitin (Ub) is a regulatory mechanism that controls nearly all
aspects eukaryotic cell biology. Ubiquitination alters properties of target proteins such as stability, subcellular
localization, intermolecular interactions, and activity and thereby regulates processes such as cell cycle
control, DNA repair, signal transduction, and immunity. The relevance of Ub signaling to human health is
underscored by the fact that its dysregulation is implicated in pathologies such as cancer, neurological
disorders, cardiovascular disease, and immune disorders and that it is a validated target for therapeutic
intervention in cancer with FDA-approved medications extending the lives of multiple myeloma patients.
Ub signaling requires the sequential interactions and activities of three enzymes, E1, E2, and E3, which act in
tandem to conjugate Ub to target proteins. Humans harbor two Ub E1s, Uba1 and Uba6, that catalyze Ub
activation and thioester transfer to distinct repertoires of tens of E2s. While Uba1 is fully dedicated to Ub
activation, Uba6 is highly unusual in that it is also capable of activating FAT10 (a Ub-like protein involved in
mitotic progression and immunity), and subsequently transferring it to a highly Uba6-specific E2, UBE2Z.
Maintenance of the integrity of Ub signaling is essential, yet mechanisms underlying Uba6 promiscuity for Ub
and FAT10, as well as the molecular rules governing specificity/promiscuity in E1/E2 interactions remain poorly
understood. After E1-E2 thioester transfer, E2~Ub intermediates interact with distinct repertoires of hundreds
of E3 ligases grouped into three families that catalyze ubiquitination of target proteins as a single molecule or
as polymeric chains linked together by specific lysine residues on Ub. Because it is a major determinant of the
functional outcome of ubiquitination, control of the type of polyUb chains assembled on substrate proteins is
essential and for reactions catalyzed by RING E3s, polyUb chain specificity is largely determined by the E2
with which they function. Despite this fundamental importance, the molecular mechanisms governing
specificity in catalysis of most polyUb linkage types remain unknown.
Through use of structural, biochemical/biophysical, and cell-based approaches, this proposal aims to discover:
1) the structural basis for substrate recognition and catalytic activities of human Ub E1 enzymes 2) the catalytic
mechanism of E1-E2 thioester transfer and molecular rules governing specificity/promiscuity in Ub E1/E2
interactions, and 3) mechanisms by which specific types of polyUb chains are catalyzed by E2/RING E3 pairs.
Ub signaling is a target for therapeutic intervention in cancer and other human pathologies and the deeper
understanding of how E1, E2, and E3 work together to control essential cellular processes that will result from
the proposed studies could provide a platform for the development of novel small molecul...

## Key facts

- **NIH application ID:** 10052157
- **Project number:** 2R01GM115568-06
- **Recipient organization:** UNIVERSITY OF TEXAS HLTH SCIENCE CENTER
- **Principal Investigator:** Shaun Olsen
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $313,680
- **Award type:** 2
- **Project period:** 2015-09-22 → 2024-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10052157

## Citation

> US National Institutes of Health, RePORTER application 10052157, Structural Biology of the Ubiquitin Conjugation System (2R01GM115568-06). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10052157. Licensed CC0.

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