# Role of ADP-ribosylation in Stress Granules

> **NIH NIH R01** · JOHNS HOPKINS UNIVERSITY · 2021 · $250,000

## Abstract

PROJECT SUMMARY
Membrane-less structures are prevalent in cells and executing unique functions (e.g., DNA repair foci and
nucleoli for making ribosomal subunits). The mechanisms by which their formation, size, number, and
dynamics are regulated, however, remain unclear. Emergent studies revealed that their formation can be partly
explained by a biophysical phenomenon known as liquid-liquid phase separation, whereby the nucleoplasm
and cytoplasm are considered complex fluids that stably segregate like oil and water. Phase separation is often
triggered when proteins bind to a common scaffold such as the nucleic acids DNA and RNA, resulting in the
condensation of proteins to form higher-order structures. We previously discovered that an under-studied
nucleic acid called poly(ADP-ribose) (PAR) is critical for the formation of a class of membrane-less organelles
implicated in cancer, virus infection and neurodegeneration called stress granules. Stress granules are
cytoplasmic RNA-protein assemblies formed in different sizes in response to stressors such as hypoxia,
oxidative stress and heat shock. Most granule components dynamically exchange with the surrounding
cytoplasm, and individual granules grow in size over time through fusion. Notably, stress granules in models of
neuropathological diseases, such as amyotrophic lateral sclerosis (ALS), have slower exchange dynamics and
are less able to fuse. However, the molecular factors that control the stress granule dynamics and fusion
(which affects size and number of granules) remain poorly understood. In this proposal, we will (1) determine
how PAR regulates phase separation in stress granules using innovative techniques to define critical
parameters of ADP-ribosylation for stress granule formation in cells and in vitro, and (2) determine whether
PAR–protein interactions regulate stress granule fusion using mutagenesis, live-cell imaging, biophysical
methods and proteomics. Projected Impact: Besides its role in stress granules, PAR is also critical for the
formation of time- and location-specific membrane-less structures, including DNA repair complexes and
nucleoli. This proposal will thus advance the field by defining critical parameters for physiologically relevant
PAR-mediated phase separation and by identifying ADP-ribosylated proteins required for these phenomena.
Given that PARPs are druggable and actively targeted by pharmaceutical companies, next-generation
inhibitors may be designed to modulate the formation and dynamics of physiological and pathological
membrane-less structures in neurological or other diseases.

## Key facts

- **NIH application ID:** 10388732
- **Project number:** 3R01GM104135-07S1
- **Recipient organization:** JOHNS HOPKINS UNIVERSITY
- **Principal Investigator:** Anthony K L Leung
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $250,000
- **Award type:** 3
- **Project period:** 2015-03-01 → 2024-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10388732

## Citation

> US National Institutes of Health, RePORTER application 10388732, Role of ADP-ribosylation in Stress Granules (3R01GM104135-07S1). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10388732. Licensed CC0.

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