# Ubiquitination during infection with Mouse Adenovirus

> **NIH NIH R21** · CHILDREN'S HOSP OF PHILADELPHIA · 2022 · $264,000

## Abstract

PROJECT SUMMARY
Viruses exert an extensive network of dynamic interactions with host components to promote infection by
dismantling cellular intrinsic and innate defenses. A central arm of viral takeover of cellular processes relies on
viral exploitation of the cellular ubiquitin system to induce degradation of host factors. However, there is a gap
in our understanding of the molecular mechanisms by which ubiquitin is harnessed by viral proteins. Here we
propose a cross-species comparison of the human and mouse adenovirus systems to explore how viruses
subvert host defenses via ubiquitin. Human adenovirus 5 (HAd5) is a prominent nuclear-replicating DNA virus
that redirects cellular Cullin E3 ubiquitin ligase activity via complex formation with two viral early proteins
(E1B55K and E4orf6). We recently developed a proteomics approach to define host proteins ubiquitinated when
the HAd5 E1B55K/E4orf6 complex is expressed. By combining our ubiquitome analysis with whole cell
proteomics, we were able to define which substrates are ubiquitinated and which are subsequently degraded as
a result of the E1B55K/E4orf6 complex. The strict species-specificity of adenovirus infection limits our ability to
study HAd in its natural host, but mouse adenovirus type 1 (MAV-1) provides an alternative tractable system.
Based on genetic similarities, MAV-1 is thought to encode orthologs (mE1B55K and mE4orf6) to the HAd5
complex, and these proteins are presumed to redirect cellular ubiquitin in a parallel fashion. We have applied
our proteomics pipeline to MAV-1 infected cells, and used global ubiquitin-profiling to identify proteins modified
and degraded by the virus. Distinct from HAd5, we discovered that MAV-1 uniquely facilitates degradation of
several canonical and non-canonical proteins involved in nucleic acid sensing and antiviral interferon signaling,
including PKR and STING. Contrary to the prevailing dogma of how the HAd5 E1B55K/E4orf6 complex employs
the E1B55K component to select ubiquitination substrates, we surprisingly discovered that mE4orf6 is sufficient
to reduce abundance of the antiviral RNA sensor PKR in a proteasome- and Cullin- dependent manner,
independent of mE1B55K. These findings collectively suggest divergence in the composition, mechanisms of
assembly, and substrate selectivity between the HAd5 and MAV-1 directed E3 ligases. An overarching
implication is that the MAV-1 and HAd5 complex exploit ubiquitin in different ways to counteract intrinsic and
innate immune responses. In Aim 1 we will leverage a multidisciplinary, quantitative proteomics approach to
systematically define the endogenous cellular ubiquitin substrates and associated pathways targeted during
MAV-1 infection. We will also determine the functional consequences of substrate ubiquitination during infection.
In Aim 2 we will establish the composition, and mechanisms of substrate selection for the MAV-1 directed E3
ligase complex and compare to HAd5. Results of our cross-species...

## Key facts

- **NIH application ID:** 10364682
- **Project number:** 5R21AI157416-02
- **Recipient organization:** CHILDREN'S HOSP OF PHILADELPHIA
- **Principal Investigator:** Matthew D. Weitzman
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $264,000
- **Award type:** 5
- **Project period:** 2021-03-04 → 2024-02-29

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10364682

## Citation

> US National Institutes of Health, RePORTER application 10364682, Ubiquitination during infection with Mouse Adenovirus (5R21AI157416-02). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10364682. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*