# Mechanisms of Enzyme Regulation by Viperin in the Cellular Antiviral Response

> **NIH NIH R35** · UNIVERSITY OF MICHIGAN AT ANN ARBOR · 2024 · $89,780

## Abstract

Project Summary
 Eukaryotic cells have developed sophisticated defenses aimed at limiting viral replication and thereby
preventing infection from escalating to other cells. This R35 MIRA application will support studies to understand
how at the biochemical level various cellular metabolic pathways are regulated as part of the innate immune
response to viral infection to disrupt virus replication. Such studies are essential for developing more effective
anti-viral therapeutics. Our studies will center around a key enzyme in the antiviral response: viperin (Virus
Inhibitory Protein; Endoplasmic Reticulum-associated, INterferon-inducible), which is strongly up-regulated in
viral infections and has been shown to restrict the infectivity of a number of important human viruses including
influenza A, HIV and hepatitis C.
 Viperin catalyzes the synthesis of the antiviral nucleotide 3’-deoxy-3’,4’-didehydro-CTP (ddhCTP) from CTP
by a radical SAM-dependent mechanism. ddhCTP has been shown to have antiviral properties against some
RNA viruses, e.g. flaviviruses, where it acts as a chain-terminating inhibitor of the viral RNA polymerase.
However, this observation does not explain the much broader antiviral properties of viperin that are associated
with its network of protein-protein interactions with viral proteins, cellular proteins important for viral replication,
and components of innate immune signaling pathways.
 Building on the results of our previous NIH-supported research, we will investigate how viperin acts to
regulate various cellular metabolic and signaling pathways that are important for establishing the antiviral state.
Our strategy is to focus on examples of viperin’s interactions with other enzymes for which there is both a well-
validated biological response and a clear biochemical rational underpinning the response. Our experimental
approach will combine detailed mechanistic and structural studies on purified enzymes with functional studies of
enzymes transfected in mammalian cell lines.
 As part of these studies, we will investigate how viperin engages with ubiquitin ligases to activate innate
immune signaling pathways and proteasomal degradation of enzymes necessary for viral replication. We will
investigate how viperin down-regulates fatty acid b-oxidation through its interactions with the mitochondrial
trifunctional enzyme (protein) complex. We will also investigate how viperin interacts with enzymes in the
cholesterol biosynthetic pathway to decrease cellular cholesterol, which is necessary for enveloped viruses to
bud from the cell membrane.
 The anticipated outcome of this project is a unified understanding of the biochemical mechanisms
underpinning viperin’s diverse antiviral functions.

## Key facts

- **NIH application ID:** 11123580
- **Project number:** 3R35GM153307-01S1
- **Recipient organization:** UNIVERSITY OF MICHIGAN AT ANN ARBOR
- **Principal Investigator:** E NEIL MARSH
- **Activity code:** R35 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $89,780
- **Award type:** 3
- **Project period:** 2024-08-01 → 2029-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/11123580

## Citation

> US National Institutes of Health, RePORTER application 11123580, Mechanisms of Enzyme Regulation by Viperin in the Cellular Antiviral Response (3R35GM153307-01S1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/11123580. Licensed CC0.

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