# Mechanisms mediating immune response upon sensing of nuclear viral DNA

> **NIH NIH R01** · PRINCETON UNIVERSITY · 2020 · $323,832

## Abstract

In order to mount intrinsic and innate immune responses to infections by DNA viruses, mammalian cells rely on
specialized proteins that recognize the viral DNA as a foreign molecule. Upon binding to viral DNA, these
sensors induce cytokine secretion, prompting neighboring cells to activate their defenses and inhibiting the
spread of infection. Recent years have seen significant progress in the understanding of processes governing
viral DNA sensing. Contrary to prior dogma, we determined that mammalian cells can distinguish viral DNA
from self-DNA in the nuclei of infected cells. The characterization of the interferon inducible protein IFI16 as the
first known nuclear sensor of viral DNA has opened a new research direction in immunity, starting to shed light
on how cells detect nuclear-replicating viruses, such as herpesviruses. We further uncovered that the human
pathogens, herpes simplex virus type 1 (HSV-1) and human cytomegalovirus (HCMV) have immune evasion
mechanisms that specifically suppress IFI16. With this knowledge, during the previously funded R01, we aimed
to dissect the mechanisms underlying nuclear IFI16 DNA sensing. We addressed questions regarding where
and when the IFI16-viral DNA binding event occurs, the properties that allow IFI16 to sense DNA, and the
functional interactions that support IFI16 antiviral responses. Our results uncovered that nuclear DNA sensing
relies on dynamic on/off sensor associations with parental viral DNA at the nuclear periphery. We
demonstrated that IFI16 oligomerization on viral DNA is essential for nucleus-derived immune signaling. We
further established that, upon binding to viral DNA, IFI16 triggers both cytokine expression and suppression of
viral gene expression. Our proposal will address several fundamental questions regarding nuclear DNA
sensing that have emerged from these findings. In Aim 1, we will define what mechanisms drive dynamic IFI16
oligomerization with HSV-1 DNA at the nuclear periphery. We will test our hypothesis that this property is
biophysically conferred via rapid and reversible liquid-phase condensation events, and delineate how these
events govern innate immunity and viral replication. Next, we will characterize mechanisms underlying the two
antiviral IFI16 functions downstream of its binding to DNA. In Aim 2, we will determine how IFI16 induces
innate immune signals upon nuclear DNA sensing. We discovered that IFI16 interacts with and activates the
DNA dependent protein kinase (DNA-PK) holoenzyme in response to herpesvirus infections. We will define
how IFI16 and the DNA damage response coordinate to stimulate innate immunity and antiviral non-
homologous end-joining. In Aim 3, we will elucidate the mechanisms underlying IFI16 restriction of virus gene
expression. We will functionally characterize the IFI16 interactions with chromatin modulators that we showed
to act as HSV-1 restriction factors. We will systematically define the pathways linking IFI16 to viral genome
hete...

## Key facts

- **NIH application ID:** 9973554
- **Project number:** 2R01GM114141-05
- **Recipient organization:** PRINCETON UNIVERSITY
- **Principal Investigator:** Ileana M. Cristea
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $323,832
- **Award type:** 2
- **Project period:** 2015-09-15 → 2024-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9973554

## Citation

> US National Institutes of Health, RePORTER application 9973554, Mechanisms mediating immune response upon sensing of nuclear viral DNA (2R01GM114141-05). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/9973554. Licensed CC0.

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