About

Professor Nicolas Fawzi leads research at the Fawzi Lab at Brown University, focusing on the structure, dynamics, and molecular interactions of large assemblies of intrinsically disordered proteins. His work particularly emphasizes liquid-liquid phase separated forms of RNA-binding proteins that are associated with inclusion formation in neurodegenerative diseases such as amyotrophic lateral sclerosis (ALS) and frontotemporal dementia, as well as protein aggregates implicated in Alzheimer’s Disease. The lab employs a combination of novel nuclear magnetic resonance (NMR) spectroscopy approaches and atomistic simulations, supplemented by biophysical and imaging methods, to determine high-resolution structures of these protein species and their toxic interactions with other macromolecules and membranes, along with their interactions with potential therapeutic agents. The tools developed in the lab are uniquely tailored to observe the detailed structure and interactions of these assemblies, whose disordered and transient nature make them difficult to study using classic structural techniques. These methods have broad applicability to other unresolved questions in biology. The lab provides research opportunities for new students in both the expression and purification of new protein targets and NMR spectroscopy of aggregation-prone proteins. The group has shared access to advanced Bruker NMR spectrometers operating at 850 MHz, 600 MHz, and 500 MHz, each equipped with cryogenic probes, maintained by the Brown Structural Biology Core Facility.

Research topics

• Biology
• Cell biology
• Biophysics
• Chemistry
• Genetics
• Biochemistry
• Computer Science
• Crystallography
• Physics
• Chemical physics
• Mathematical analysis
• Computational biology
• Virology
• Molecular biology
• Organic chemistry
• Mathematics
• Computational chemistry
• Chemical engineering
• Geometry
• Thermodynamics
• Library science
• Materials science

Selected publications

• Visualizing TERRA RNA G-quadruplex Unfolding in FUS Biomolecular Condensates

  Journal of Molecular Biology · 2026-03-06

  articleOpen accessSenior authorCorresponding

  RNA G-quadruplexes (rG4s) are remarkably stable secondary structures with critical regulatory roles in gene expression, RNA metabolism, and telomere maintenance. However, their behavior within cells remains controversial, partly due to challenges in detecting rG4s in complex environments. Here, we use solution NMR spectroscopy to investigate how condensates formed by the low-complexity and RGG domains of the RNA-binding protein FUS affect the structure of TERRA, a highly stable model rG4. We show that FUS LC-RGG1 interacts with TERRA in dilute solution and that binding perturbs, but does not disrupt, the G-quadruplex structure. When co-phase separated with FUS LC-RGG1, however, NMR signatures of TERRA's folded state disappear, and the remaining observable resonances indicate an unfolded conformation, even in buffer containing potassium where TERRA rG4 is exceptionally stable when outside a condensate. Quantitative comparisons with a mutant form of TERRA, used as a baseline for fully unfolded RNA, suggest that at minimum a third of TERRA RNA becomes unfolded in the condensed phase. Thus, our results demonstrate that condensates can shift the structural ensemble of rG4 towards unfolded species, offering a potential mechanistic explanation for their apparent lack of stability in vivo and revealing how phase-separated environments may actively modulate RNA structure and function.

  PublisherDOI

• BPS2026 – Molecular details of RNA in biomolecular condensates

  Biophysical Journal · 2026-02-01

  articleSenior author
  PublisherDOI

• Defining RNA oligonucleotides that reverse deleterious phase transitions of RNA-binding proteins with prion-like domains

  Molecular Cell · 2026-01-01 · 4 citations

  articleOpen access
  PublisherOA PDFDOI

• Breaking β-sheets in FUS prion-like domain preserves phase separation and function but prevents aggregation and toxicity

  bioRxiv (Cold Spring Harbor Laboratory) · 2026-02-18 · 1 citations

  articleOpen accessSenior authorCorresponding

  Abstract The RNA-binding protein Fused in Sarcoma (FUS) undergoes phase separation associated with RNA processing. However, the prion-like low complexity (LC) domain of FUS forms solid-like aggregates in neurodegenerative diseases. Whether the formation of β-sheet structure associated with pathology is also physiologically/functionally relevant is debated. Similarly, if mislocalization alone or concomitant aggregation is responsible for FUS gain-of-function toxicity remains to be probed. Here, we introduce β-sheet breaking proline residues into FUS LC with the goal of preventing cross-β-driven aggregation without disrupting essential functions and phase separation. β-sheet-deficient FUS variants maintain native-like global motions, disorder, and phase separation, but no longer show a liquid-to-solid transition (LST). Biochemical partitioning, cellular localization, and auto- and cross-regulatory functions of FUS all remain essentially unchanged. Conversely, FUS-induced neurodegeneration in several Drosophila models is drastically reduced. These findings suggest a strategy for mitigating disease-related toxicity through backbone structure modulation to prevent prion-like domain protein aggregation. GRAPHICAL ABSTRACT SUMMARY The RNA-binding protein Fused in Sarcoma (FUS) undergoes phase separation as part of its physiological function but can aberrantly aggregate into solid-like assemblies in amyotrophic lateral sclerosis and frontotemporal dementia. To dissect the role of β-sheets in both function and pathological transition, we engineered β-sheet-preventing FUS variants via targeted proline residue insertions in the prion-like disordered region. These variants retained native structure, motions, and phase behavior yet showed dramatically reduced aggregation, both as an isolated prion-like domain and in full-length FUS. Crucially, these variants maintained a panel of FUS cellular functions that depend on FUS condensation but prevented FUS toxicity in fly models of neurodegeneration. Our findings implicate β-sheets as key drivers of FUS condensate maturation and neuronal toxicity, highlighting β-sheet modulation as a therapeutic strategy against FUS-related neurodegeneration. HIGHLIGHTS Targeted proline additions disrupt β-sheet formation in FUS without altering native conformations, dynamics, or phase separation behavior β-sheet-deficient FUS variants prevent aggregation and liquid-to-solid transitions while retaining key biological functions In vivo models reveal attenuated toxicity of β-sheet-deficient FUS in Drosophila β-sheets are identified as central drivers of condensate maturation and neuronal death, offering a therapeutic entry point for modulating prion-like domain pathology

  PublisherOA PDFDOI

• The glycine-arginine-rich motif of 53BP1 modulates RNA interactions necessary for its liquid-liquid phase separation during DNA Damage Response

  bioRxiv (Cold Spring Harbor Laboratory) · 2026-01-30 · 1 citations

  article

  ABSTRACT The DNA damage response relies on the rapid assembly of repair factors into foci with properties of liquid-liquid phase separation, driven by de novo transcription of damage-induced RNAs. 53BP1 is a key component of these condensates, yet the molecular determinants driving this process remain unknown. Here, through computational, structural and in vitro approaches, we identify the oligomerization domain of 53BP1 and its glycine-arginine-rich (GAR) motif as crucial for RNA interactions and phase separation. Biophysical characterization reveals that 53BP1-RNA condensates can progressively mature into a more stable state, and that GAR mutants display aberrant material properties. Using a cellular model of telomere fusion events, we demonstrate that the GAR motif is essential for 53BP1-mediated DNA repair, which depends on the combined contributions of RNA binding and appropriate condensate biophysical properties. Therefore, RNA-driven 53BP1 condensation is functionally required to maintain genome integrity.

  PublisherDOI

• Molecular insights into the effect of 1,6-hexanediol on FUS phase separation

  The EMBO Journal · 2025-04-25 · 26 citations

  articleOpen accessSenior author

  The alkanediol 1,6-hexanediol has been widely used to dissolve liquid-liquid phase-separated condensates in cells and in vitro, but the details of how it perturbs the molecular interactions underlying liquid-liquid assembly remain unclear. In this study we use a combination of microscopy, nuclear magnetic resonance (NMR) spectroscopy, molecular simulation, and biochemical assays to probe how alkanediols suppress phase separation and why certain isomers are more effective. We show that alkanediols of different lengths and configurations are all capable of disrupting phase separation of the RNA-binding protein Fused in Sarcoma (FUS), although potency varies depending on both geometry and hydrophobicity, which we measure directly. Alkanediols induce a shared pattern of changes to the chemical environment of the protein, to different extents depending on the specific compound. Furthermore, we use lysozyme as a model globular protein to demonstrate that alkanediols decrease the proteins' thermal stability, which is consistent with the view that they disrupt phase separation driven by hydrophobic groups. Conversely, 1,6-hexanediol does not disrupt charge-mediated phase separation, such as FUS RGG-RNA and poly-lysine/poly-aspartic acid condensates. All-atom simulations show that hydroxyl groups in alkanediols mediate interactions with the protein backbone and polar amino acid side chains, while the aliphatic chain allows contact with hydrophobic and aromatic residues, providing a molecular picture of how amphiphilic interactions disrupt FUS phase separation.

  PublisherOA PDFDOI

• AlphaFlex: Ensembles of the human proteome representing disordered regions

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-11-25 · 1 citations

  preprintOpen access

  Over a third of residues in the canonical human proteome are predicted to fall within intrinsically disordered protein regions (IDRs), which do not adopt stable folded structures. These IDRs play critical roles in biological regulation and organization, including as targets for post-translational modifications, scaffolds and mediators of biomolecular condensates. To address the pressing need for valid structural models providing biological relevance and enabling functional insight, we developed the AlphaFlex workflow, using IDPConformerGenerator or IDPForge to calculate fully atomistic conformer ensembles for proteins predicted to have disordered regions, modeled in the context of highly confident folded domains from AlphaFold2. We illustrate our approach by generating conformational ensembles of the human proteins in the AlphaFold2 database, with completed AlphaFlex models deposited in the Protein Ensemble Database that is mirrored in UniProt. This transformative resource of AlphaFlex ensembles provides more realistic and biologically relevant full-length protein models for proteins with IDRs, which we illustrate for scaffold proteins with folded domains connected by IDRs, those with IDRs that interact with folded domains, regulatory and condensate proteins requiring exposed binding elements, and a conditionally folding IDR.

  PublisherOA PDFDOI

• The Structural Basis for RNA Binding and Recognition of the Disordered Prion-Like Domain of TDP-43

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-12-23 · 1 citations

  articleOpen accessSenior authorCorresponding

  Abstract Though the structural details of how RNA interacts with folded RNA-binding domains are well established, how intrinsically disordered regions (IDRs) found in a large fraction of RNA-binding proteins mediate contacts with RNA and if they contribute to binding specificity has not been extensively characterized. The human RNA-binding protein TDP-43 is associated with many RNA processing functions that require its predominantly disordered C-terminal domain (CTD) that forms disease-associated inclusions in ALS, and other neurodegenerative conditions. Here, we demonstrate that TDP-43 CTD directly interacts with RNA primarily via a region of the IDR composed of clustered positively charged residues. Large RNAs act as a multivalent scaffold for CTD monomers, inducing the α-helical segment of TDP-43 CTD to form multimeric protein-protein structures. Additionally, we probe the nucleotide base and amino acid specificity of CTD-RNA interactions, showing that arginine, aromatic and polar residues display a preference for U and G nucleic acid bases over C and A. Finally, we probe the molecular basis for the strong binding interaction between TDP-43 and G4 quadruplex structures and discover similarly avid interactions with cytosine-rich DNA I-motifs. This work deepens our understanding of how disordered regions of proteins contribute to RNA recognition, drive function, and contribute to disease. Graphical Abstract

  PublisherOA PDFDOI

• Phase separation of NELFE modulates chromatin accessibility to promote dichotomous signaling pathways in hepatocellular carcinoma

  Research Square · 2025-04-25 · 1 citations

  preprintOpen accessSenior author
  PublisherOA PDFDOI

• Site-specific methionine oxidation alters structure and phase separation of TDP-43 C-terminal domain

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-12-16 · 1 citations

  articleOpen accessSenior author

  TAR DNA binding protein 43 (TDP-43), a key protein linked to ALS pathology, undergoes phase separation and forms functional assemblies via condensation within cells. The conserved region (CR) within its C-terminal domain (CTD) mediates self-assembly through helix-helix interactions, while the flanking intrinsically disordered regions (IDRs) contribute to phase separation through transient interactions involving aromatic and hydrophobic residues. The CTD contains ten methionine residues distributed equally between these regions, making it particularly susceptible to oxidative modifications. While methionine oxidation is known to impair phase separation, neither the precise mechanism nor the specific contribution of methionines in the CR compared to the IDRs has been determined. Here, we combine NMR spectroscopy and all-atom molecular dynamics (MD) simulations to reveal if and how methionine oxidation in each region differentially affects CTD structure and phase separation. We demonstrate that all methionine residues are vulnerable to oxidation, leading to distinct regional effects: oxidation of CR methionines disrupts helical structure and directly impairs intermolecular helical association, while oxidation of IDR methionines disrupts long-range contacts. Hence, oxidation of methionines in both regions contributes to impaired phase separation, albeit through different mechanisms. These findings establish methionines as critical redox-sensitive modulators of TDP-43 phase behavior and provide molecular insights into how oxidative stress may contribute to TDP-43 dysregulation in neurodegenerative diseases.

  PublisherOA PDFDOI

Recent grants

• Residue-by-residue details of FUS protein phase separation and aggregation

  NIH · $1.7M · 2022–2026

• CAREER: Structural aspects of glutamine-rich domain liquid-liquid phase separation in transcription and RNA processing

  NSF · $914k · 2019–2024

• Functional and Pathological Interactions of TDP-43

  NIH · $3.6M · 2020–2025

• Turning off the molecular switch for pathological self-assembly of FUS

  NIH · $1.6M · 2016–2022

Frequent coauthors

• Anastasia C. Murthy

  Brown University

  80 shared

• Veronica H. Ryan

  National Institute of Neurological Disorders and Stroke

  66 shared

• G. Marius Clore

  National Institute of Diabetes and Digestive and Kidney Diseases

  61 shared

• Theodora Myrto Perdikari

  Brown University

  59 shared

• Jeetain Mittal

  Texas A&M University

  55 shared

• Alexander E. Conicella

  John Brown University

  47 shared

• Teresa Head‐Gordon

  University of California, Berkeley

  46 shared

• Mandar T. Naik

  Brown University

  35 shared

Education

• B.S., Bioengineering and Marketing

  University of Pennsylvania

• Ph.D., Bioengineering

  University of California, Berkeley and UCSF