# Structural basis of mRNA decapping in poxviruses

> **NIH NIH F32** · UNIVERSITY OF CALIFORNIA, SAN FRANCISCO · 2020 · $65,310

## Abstract

Project Summary / Abstract
 Viruses have developed many unique strategies to evade the host immune response in the pursuit of a
common goal: to proliferate. In fact, most viruses use multiple tactics simultaneously to achieve this goal. Such
is the case for poxviruses which have at least three mechanisms to prevent their hosts from detecting dsRNA,
thereby preventing the activation of host innate immune sensors. One of these mechanisms is to use viral
encoded decapping enzymes D9 and D10 to clear accumulating dsRNA by removing the protective 5¢ cap of
host and viral mRNAs, committing them to degradation by cellular 5¢-3¢ exoribonuclease Xrn1. The fact that D9
and D10 are expressed at different stages of the viral replication cycle and early studies indicate they recognize
capped mRNA differently suggests D9 and D10 have distinct functions, perhaps targeting different mRNAs
during infection. However, despite the significant role these enzymes play in host immune evasion and the
extensive body of literature describing poxvirus pathogenesis, we lack an effective molecular understanding of
how they both recognize their capped mRNA and catalyze cap hydrolysis to evade the host immune response.
 This research plan seeks to combine biochemistry, structural biology and virology to establish the
molecular basis with which these enzymes recognize and hydrolyze their substrates, and how their substrate
specificity contributes to poxvirus pathogenesis. To determine if substrate specificity is conferred during
substrate binding or the catalytic step, in vitro binding and activity assays will be performed using various
substrates relevant to the different mRNAs present during poxvirus infection. The molecular determinants that
govern substrate recognition will be identified using high- and low-resolution structural techniques. The
combination of high- and low-resolution techniques will build a more complete understanding of the specific
molecular interactions, conformational changes, and higher order assembly that contribute to function.
Mutational analyses using in vitro binding and activity assays in addition to cell-based infectivity assays will be
used to link structure to phenotype and to validate the biochemical and biological relevance of the structural
model. Lastly, protein-protein interaction partners will be identified using affinity purification coupled with mass
spectrometry to determine if substrates are selected by enzyme-substrate binding per se or if protein cofactors
assist in recruiting D9 and D10 to target mRNAs. Together, these studies will provide a molecular understanding
of how substrate recognition and protein-protein interactions with poxvirus decapping enzymes control target
mRNA selection and cap cleavage during infection. Understanding poxvirus decapping enzyme activity at the
molecular level is an important step toward a comprehensive model of mRNA stability during poxvirus infection
that can be used in developing poxvirus tools f...

## Key facts

- **NIH application ID:** 9959189
- **Project number:** 5F32GM133084-02
- **Recipient organization:** UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
- **Principal Investigator:** Jessica Peters
- **Activity code:** F32 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $65,310
- **Award type:** 5
- **Project period:** 2019-06-01 → 2021-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9959189

## Citation

> US National Institutes of Health, RePORTER application 9959189, Structural basis of mRNA decapping in poxviruses (5F32GM133084-02). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/9959189. Licensed CC0.

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