# Cis and Trans-acting Factors that Modulate Ebola Virus RNA Synthesis

> **NIH NIH P01** · WASHINGTON UNIVERSITY · 2020 · $303,000

## Abstract

Summary 
Filoviruses, which include the Ebola viruses (EBOV) and Marburg viruses (MARV) are non-segmented, 
negative-sense RNA viruses (NNSVs) that cause severe disease. Fundamental to filovirus replication is the 
viral RNA synthesis machinery. Viral proteins, in concert with cis- and trans-acting factors, regulate the viral 
RNA-dependent RNA polymerase (RDRP). However, we lack a comprehensive understanding as to how such 
factors works together to regulate viral RNA synthesis. This project (Project 1) will build upon several novel 
observations by the Basler lab and upon data generated in Projects 2 and 3 of this program to determine the 
mechanisms by which specific cis-acting sequences and trans-acting proteins modulate filovirus replication. It 
will also define the functional consequences of these mechanisms for replication. One observation was the 
identification of short upstream open reading frames (uORFs) in the 5' UTRs of the EBOV VP35, VP30, VP24 
and L mRNAs as cis-acting regulators of protein expression. The L uORF was further demonstrated to 
modulate L protein translation in response to cell stress and eIF-2 phosphorylation levels. We hypothesize 
that this provides a mechanism by which the virus regulates expression of its RDRP machinery in response to 
the innate immune status of the host cell. We will use reporter gene-based approaches and ribosomal 
footprinting methods to determine how filoviral UTRs and uORFs modulate mRNA translation and design 
mutant recombinant EBOVs to assess these functions in the context of infection. A second finding was the 
identification of several previously unrecognized sites in both EBOV and MARV where substantial mRNA 
editing occurs. This is similar to the previously recognized editing of the EBOV glycoprotein (GP) mRNA, 
where the viral RDRP adds non-template encoded “As” at a site that corresponds to a specific polyU stretch on 
the template genomic RNA. Because the determinants of editing frequency by the filoviral RDRP remain 
incompletely defined and because the biological significance of the edited mRNAs' translation products is 
unclear, we will use a reconstituted viral RDRP complex and deep sequencing approaches to define cis-acting 
elements that regulate editing events. Finally, we and others have identified trans-acting factors such as the 
cellular proteins LC8, PACT and, DRBP76 as modulators of EBOV RNA synthesis. These observations 
support the hypothesis that host factors will modulate viral RDRP function in significant ways. Studies 
performed in Project 2 of this application will define interactions among the viral proteins that comprise the 
EBOV RDRP complex. Project 3 will comprehensively evaluate host factors for modulation of virus replication. 
Project 1 will use established transfection-based assays of viral RNA synthesis to evaluate the impact of LC8, 
PACT and, DRBP76 and newly identified interactions on the viral RDRP and define mechanisms of action. In 
total, t...

## Key facts

- **NIH application ID:** 9955175
- **Project number:** 5P01AI120943-05
- **Recipient organization:** WASHINGTON UNIVERSITY
- **Principal Investigator:** Christopher F Basler
- **Activity code:** P01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $303,000
- **Award type:** 5
- **Project period:** 2016-07-07 → 2023-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9955175

## Citation

> US National Institutes of Health, RePORTER application 9955175, Cis and Trans-acting Factors that Modulate Ebola Virus RNA Synthesis (5P01AI120943-05). Retrieved via AI Analytics 2026-05-25 from https://api.ai-analytics.org/grant/nih/9955175. Licensed CC0.

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