# Mechanistic studies of genomic RNA dimerization in an oncoretrovirus

> **NIH NIH F30** · PENNSYLVANIA STATE UNIV HERSHEY MED CTR · 2020 · $50,520

## Abstract

PROJECT ABSTRACT
 Retroviruses are single-stranded RNA viruses that cause cancers and immunodeficiency diseases in
humans and animals. Our laboratory studies Rous sarcoma virus (RSV), an avian retrovirus that causes solid
tumors in domesticated fowl, as a model for dissecting the molecular underpinnings of retroviral assembly. Our
discovery that the RSV structural protein Gag transiently travels through the nucleus in a Crm1-dependent
fashion challenged the traditional view of retroviral assembly. Treatment with a Crm1 inhibitor or mutation of
the nuclear export signal (NES) effectively traps RSV Gag in the nucleus, allowing us to further study the role
of Gag in the nucleus. Recent studies have revealed additional retroviral Gag proteins that undergo nuclear
localization, suggesting there may be common functions of Gag within the nucleus.
 Retroviruses are unique in that they package two copies of their genome as non-covalently linked
genomic RNA dimers. Genome dimerization is facilitated by cis-acting sequences located in the 5’UTR of the
viral RNA. Dimerization of the genome is conserved in orthoretroviruses and is required for viral replication.
Despite its critical importance in replication, the mechanisms underlying genome dimerization within infected
cells remains poorly understood. RSV affords a unique opportunity to investigate genome dimerization using
our extensive toolbox of genetic, biochemical and imaging methods because we can readily manipulate the
subcellular localization of Gag with our well-characterized collection of viral mutants. In recent work, we have
developed methods to visualize fluorophore-tagged RSV Gag proteins co-localized with viral genomic RNA in
the cell. Our experiments suggest nuclear trafficking of Gag is required for the efficient packaging of retroviral
genomic RNA. This proposal thus aims to understand the mechanism governing genome dimerization in RSV,
and we will test the hypothesis that nuclear trafficking of Gag plays a role in facilitating genome dimerization.
 In these studies, we will utilize the MS2 and Bgl RNA labeling system to visualize two distinct viral RNA
populations to examine genome dimerization. This approach will allow us to determine the subcellular location
of dimerization; whether there is preferential formation of heterodimers, which contain two genetically distinct
viral genomes, or homodimers, composed of two identical viral genomes; and whether dimerization occurs in a
co-transcriptional manner. We will also examine the role of nuclear Gag in genome dimerization and determine
whether RSV Gag initially binds monomers or dimers. Studies that express the viral RNA and Gag in trans will
investigate whether Gag facilitates genome dimerization within different compartments of the cell. The findings
from this proposal will greatly contribute to the understanding of this critical step in the replication cycle and
may provide support for future anti-retroviral therapeutics. Overall, this pr...

## Key facts

- **NIH application ID:** 9825535
- **Project number:** 5F30CA214010-04
- **Recipient organization:** PENNSYLVANIA STATE UNIV HERSHEY MED CTR
- **Principal Investigator:** Eunice C Chen
- **Activity code:** F30 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $50,520
- **Award type:** 5
- **Project period:** 2017-01-09 → 2021-01-08

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9825535

## Citation

> US National Institutes of Health, RePORTER application 9825535, Mechanistic studies of genomic RNA dimerization in an oncoretrovirus (5F30CA214010-04). Retrieved via AI Analytics 2026-05-21 from https://api.ai-analytics.org/grant/nih/9825535. Licensed CC0.

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