# Regulation of DNA Damage and Innate Immunity During the Productive Phase of the HPV Life Cycle

> **NIH NIH R21** · UNIV OF NORTH CAROLINA CHAPEL HILL · 2021 · $233,250

## Abstract

The productive phase of the HPV life cycle is restricted to the uppermost layer of the epithelium in cells that have normally exited the cell cycle. The E7 protein alters cell cycle regulation, pushing differentiating cells back into the cell cycle to allow for viral genome amplification to 1000s of copies per cell and virion production. Cell cycle deregulation by E7 leads to genomic instability that is a driving force in cancer development. Our long-term goal is to understand mechanisms that regulate productive viral replication, which is important to understanding how HPV causes cancer. While caspase activation is typically viewed as an anti-viral response, HPV requires low level activation of caspases belonging to the mitochondrial pathway of apoptosis for productive replication. In this apoptotic pathway, cell death is initiated by mitochondrial membrane permeabilization (MOMP), which normally induces rapid cell death. Interestingly, HPV-induced caspase activation is not accompanied by morphological features of apoptosis, suggesting that HPV may restrain MOMP to limit caspase activity. How HPV is able to take advantage of pro-viral caspase functions by blocking apoptosis is currently unclear. Caspase cleavage of the HPV E1 helicase is required for productive replication, indicating that caspases directly regulate productive replication. However, caspase activation induces DNA damage and activates DNA damage response (DDR) pathways through JNK1/2, and we have found JNK1/2 activation increases upon differentiation. While the importance of DDR pathways (e.g. ATM and ATR) in driving productive replication is well-established, the contribution of caspase activity to DDR regulation is unknown. In the absence of apoptotic caspase activity, cytosolic release of mtDNA by MOMP is sensed by the cGAS-STING pathway, leading to induction of Type I Interferons (IFN). Intriguingly, we have found that apoptotic caspase activity is necessary to block a Type I as well as Type III IFN response upon differentiation. These results indicate that caspase activity indirectly supports productive replication through effects on host cell processes in a non-lethal manner. We hypothesize that HPV exploits non-apoptotic functions of caspases upon epithelial differentiation to facilitate the productive phase of the viral life cycle. In Aim 1, we will determine if HPV induces limited caspase activation and DNA damage through minority MOMP by using innovative techniques to monitor MOMP on a single cell level; by determining if caspase activity is non-lethal in differentiating cells; and by examining the effect of caspase inhibition on DNA damage and DDR activation. In Aim 2, we will determine how HPV uses caspase activity to block the IFN response upon differentiation by examining a role for MOMP and mtDNA release in stimulating IFN production upon caspase inhibition, and by determining if caspase activity blocks the cGAS-STING DNA sensing pathway. Completion of these studies...

## Key facts

- **NIH application ID:** 10108694
- **Project number:** 1R21AI156158-01
- **Recipient organization:** UNIV OF NORTH CAROLINA CHAPEL HILL
- **Principal Investigator:** CARY A MOODY
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $233,250
- **Award type:** 1
- **Project period:** 2021-04-15 → 2023-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10108694

## Citation

> US National Institutes of Health, RePORTER application 10108694, Regulation of DNA Damage and Innate Immunity During the Productive Phase of the HPV Life Cycle (1R21AI156158-01). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10108694. Licensed CC0.

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