# Functional regulation of an arenavirus polymerase by the viral matrix protein and RNA ligands

> **NIH NIH F31** · HARVARD MEDICAL SCHOOL · 2020 · $31,173

## Abstract

Arenaviruses are responsible for significant zoonotic human illnesses and mortality across the globe,
inducing Lassa fever in West Africa, lymphocytic choriomeningitis, and numerous regional hemorrhagic fever
diseases in South America. These viruses are unable to infect their host cells without the delivery of a large
transcriptionally primed replication and gene expression complex, consisting of the viral polymerase (L) directly
bound to the nucleoprotein-encapsidated negative-sense genomic RNA (vRNA) segments. Arenavirus L
proteins play essential roles in nearly every step of the virus infection cycle, including gene expression,
genome replication, and formation of the infectious viral ribonucleoprotein. An accurate mechanistic
understanding of L proteins has been hindered by a lack of available biochemical systems and structural
models for these multifunctional enzymes. Machupo virus (MACV) is an arenavirus responsible for localized
outbreaks of Bolivian hemorrhagic fever. Our lab has pioneered the use of MACV L as a model for arenavirus
replication studies, developing multiple experimental systems for the purification and functional analyses of a
full-length MACV L. Previous work in our lab has revealed that the catalytic activity of the MACV L protein is
completely inhibited due to direct binding by the viral matrix protein (Z). As a result, the L-Z complex is locked
in an inactive state on the viral RNA promoter. Moreover, a recently proposed model has suggested that the
interaction of L with the 5' termini of the genome segments (5' vRNA) mediates enhanced RNA synthesis
activity. The central hypothesis for my proposal is that the RNA synthesis and cap-snatching domains
of MACV L are under opposing regulatory influences by the viral matrix protein (Z) and the terminal 5'
genomic RNA sequences. The experiments outlined for this project will address the following gaps in our
understanding of the MACV system and arenavirus biology: i) the structural mechanisms underlying the
regulation of arenavirus L RNA synthesis by its protein and RNA ligands, ii) the biochemical role of the 5'
vRNA in modulating L activity, and iii) the catalytic activity and regulation of the MACV L cap-snatching
machinery Findings from this project will offer novel insight into the unanswered questions of arenavirus
biology, and will certainly be applicable in downstream endeavors for the development of targeted antiviral
therapeutic strategies. Our lab has recently made significant progress in the field of polymerase structural
biology with the resolved atomic model of the vesicular stomatitis virus (VSV) L protein in complex with its
phosphoprotein cofactor. Moreover, our lab has developed the only available in vitro and cell-based systems
for the study of MACV L biochemical functions and regulation by its unique cofactors (Z and the 5' vRNA).
These experimental systems make MACV the ideal candidate for L structure-function studies. Collectively,
these efforts will sig...

## Key facts

- **NIH application ID:** 9981617
- **Project number:** 5F31AI133689-03
- **Recipient organization:** HARVARD MEDICAL SCHOOL
- **Principal Investigator:** Jesse Dylan Pyle
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $31,173
- **Award type:** 5
- **Project period:** 2018-08-01 → 2021-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9981617

## Citation

> US National Institutes of Health, RePORTER application 9981617, Functional regulation of an arenavirus polymerase by the viral matrix protein and RNA ligands (5F31AI133689-03). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/9981617. Licensed CC0.

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