# FUS Gene: Structure, Function, and Clinical Significance


## Key Takeaways

- The *FUS* gene, located at 16p11.2, encodes a multifunctional DNA/RNA-binding protein critical for transcription, splicing, and DNA repair, with mutations linked to neurodegenerative diseases like ALS (ALS6) and various mesenchymal/hematopoietic malignancies through chromosomal translocations.
- Pathogenic mutations in *FUS*, particularly in the Nuclear Localization Signal (NLS) domain (e.g., R521C, P525L), disrupt nuclear import, leading to cytoplasmic mislocalization, aggregation, and impaired cellular functions, driving neurotoxicity in ALS.
- *FUS* gene translocations generate oncogenic fusion proteins, such as FUS-DDIT3 in myxoid liposarcoma and FUS-ERG in acute myeloid leukemia, which aberrantly regulate gene expression and block cellular differentiation, serving as key diagnostic markers and therapeutic targets.
- Therapeutic strategies for FUS-related disorders include antisense oligonucleotides (ASOs) to reduce FUS mRNA levels, HDAC inhibitors to restore histone acetylation, and targeted therapies like trabectedin for FUS-fusion sarcomas by interfering with oncogenic transcription.
- FUS plays a role in host-pathogen interactions, acting as a restriction factor against Kaposi's Sarcoma-Associated Herpesvirus (KSHV) by binding and degrading viral mRNAs, and interacting with HIV-1 and influenza A virus proteins.

---

## Executive Summary & Key Metadata

The **FUS** gene (Fused in Sarcoma; also known as **TLS**, Translocated in Liposarcoma) encodes a multifunctional DNA/RNA-binding protein that is ubiquitously expressed and highly conserved across metazoans. FUS belongs to the FET protein family (FUS, EWSR1, TAF15), characterized by an N-terminal low-complexity prion-like domain and a C-terminal canonical RNA-recognition motif (RRM) flanked by zinc-finger and arginine-glycine-glycine (RGG) domains. The protein is predominantly nuclear, where it participates in transcription, pre-mRNA splicing, DNA damage repair, microRNA biogenesis, and maintenance of genomic integrity. Pathologically, FUS is a central player in two distinct disease spectra: (1) neurodegenerative disorders, particularly amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), where mutations cause cytoplasmic mislocalization and aggregation; and (2) mesenchymal and hematopoietic malignancies, where chromosomal translocations generate chimeric oncoproteins such as FUS-DDIT3 (myxoid liposarcoma), FUS-ERG (acute myeloid leukemia), and FUS-CREB family fusions (various sarcomas). This manual provides a comprehensive, biophysically detailed reference on FUS genomic architecture, protein structure, signaling networks, pathogenic mutations, and therapeutic implications.

| **Attribute** | **Value** |
|---|---|
| HGNC Symbol | FUS |
| UniProt Accession | P35637 |
| Representative PDB ID | 6G99 (LC domain fibril), 4FQ3 (RRM domain) |
| Chromosomal Locus | 16p11.2 |
| Primary Molecular Function | DNA/RNA binding; transcription regulation; pre-mRNA splicing; DNA repair; phase separation |
| Disease & Pathology Associations | ALS6 (amyotrophic lateral sclerosis type 6); FTD-FUS; myxoid liposarcoma; low-grade fibromyxoid sarcoma; acute myeloid leukemia; Ewing-like sarcomas; essential tremor (risk) |

---

## 1. Genomic Locus, Chromosomal Organization & Isoforms

### 1.1 Chromosomal Location and Gene Structure

The human *FUS* gene is located on the short arm of chromosome 16 at band p11.2 (chr16:31,180,110-31,194,871; GRCh38/hg38). The gene spans approximately 14.7 kilobases of genomic DNA and is oriented on the minus strand. The locus is gene-dense, with neighboring genes including *SEPT1* (septin 1) telomerically and *MAPK8IP3* (JIP3) centromerically. The region 16p11.2 is notable for copy-number variation associated with neurodevelopmental phenotypes, although *FUS* itself is rarely subject to large deletions or duplications in disease.

The *FUS* gene comprises 15 exons, with the translation initiation codon located in exon 2 and the stop codon in exon 15. Exon 1 is entirely untranslated (5' UTR) and contains a CpG island that serves as the primary promoter region. The promoter lacks a canonical TATA box but contains multiple GC boxes (SP1 binding sites) and a CCAAT box, consistent with housekeeping gene expression. DNase I hypersensitivity mapping and chromatin immunoprecipitation (ChIP) data from ENCODE reveal active enhancer marks (H3K27ac, H3K4me1) in intron 1 and upstream of exon 1, suggesting the presence of cell-type-specific enhancer elements. A conserved non-coding element in intron 13 has been implicated in neuronal-specific expression regulation.

### 1.2 Transcription Factor Binding and Regulatory Architecture

The FUS promoter is bound by several transcription factors, including SP1, ETS family members, and NF-κB. Notably, FUS autoregulates its own expression through a negative feedback loop: the FUS protein binds to its own pre-mRNA and promotes exon 7 skipping, generating a transcript that is targeted for nonsense-mediated decay (NMD). This autoregulatory mechanism is critical for maintaining FUS protein homeostasis, and its disruption by ALS-linked mutations in the nuclear localization signal (NLS) leads to elevated FUS mRNA and protein levels.

Single-nucleotide polymorphisms (SNPs) in the FUS promoter and 3' UTR have been associated with altered FUS expression in essential tremor and sporadic ALS, although the effect sizes are modest. The 3' UTR contains multiple binding sites for microRNAs, including miR-141, which has been shown to downregulate FUS expression in neuroblastoma cell lines, thereby modulating proliferation, migration, and cisplatin chemosensitivity [1].

### 1.3 Alternative Splicing and Isoforms

The *FUS* gene undergoes extensive alternative splicing, producing multiple transcript variants. The major transcript (NM_004960.4) encodes the canonical 526-amino-acid protein. Alternatively spliced isoforms include:

- **FUS-Δexon5**: Lacks exon 5, resulting in an in-frame deletion of 30 amino acids within the glycine-rich region. This isoform is enriched in testis and brain.
- **FUS-Δexon7**: Lacks exon 7, which is the NMD-sensitive isoform involved in autoregulation.
- **FUS-Δexon8**: Lacks exon 8, producing a truncated protein that retains the N-terminal low-complexity domain but lacks the RRM and zinc finger. This isoform is expressed at low levels in multiple tissues.
- **FUS-Δexon14**: Lacks exon 14, resulting in a frameshift and premature stop codon. This isoform is also NMD-sensitive.

In addition to these canonical splice variants, a dual-coding feature of the *FUS* mRNA has been described: an alternative open reading frame (altORF) nested within the main coding sequence encodes a 170-amino-acid protein termed **altFUS** [2]. AltFUS is translated from a non-AUG start codon in a different reading frame and is endogenously expressed in human tissues, particularly in motor cortex. AltFUS localizes to mitochondria and contributes to FUS-mediated toxicity in ALS models, suggesting that the *FUS* locus encodes two functionally distinct proteins whose combined activities influence disease phenotype [2].

---

## 2. 3D Protein Domain Architecture & Structural Biology

### 2.1 Primary Structure and Domain Organization

The FUS protein (526 amino acids, ~53 kDa) is organized into distinct functional domains from N-terminus to C-terminus:

| **Domain** | **Residues** | **Function** |
|---|---|---|
| QGSY-rich low-complexity (LC) domain | 1–165 | Prion-like; drives phase separation and aggregation; transcriptional activation |
| Glycine-rich region | 166–267 | Flexible linker; protein-protein interactions |
| RRM (RNA Recognition Motif) | 285–371 | Binds RNA and single-stranded DNA |
| Zinc finger (ZnF, C2H2 type) | 371–422 | Stabilizes nucleic acid binding; contributes to DNA repair foci |
| RGG1 domain | 422–453 | Arginine-glycine repeats; RNA binding; methylation sites |
| RGG2 domain | 453–501 | RNA binding; nuclear import/export modulation |
| Nuclear Export Signal (NES) | 129–141 | CRM1-dependent nuclear export |
| Nuclear Localization Signal (NLS) | 514–526 | Proline-tyrosine NLS; recognized by Transportin-1 (TNPO1) |

### 2.2 Low-Complexity Domain and Phase Separation

The N-terminal LC domain (residues 1–165) is enriched in glutamine (Q), glycine (G), serine (S), and tyrosine (Y) residues and is structurally reminiscent of yeast prion domains. Solid-state NMR studies of FUS LC domain fibrils revealed a kinked β-sheet architecture, with each molecule contributing two β-strands connected by a short loop [3]. This "steric zipper" arrangement underpins the ability of FUS to undergo liquid-liquid phase separation (LLPS), forming reversible condensates that regulate RNA metabolism. The LC domain also mediates the formation of hydrogels and amyloid-like fibrils under pathological conditions. Tyrosine residues within the LC domain are critical for π-π interactions that stabilize phase-separated droplets, and their phosphorylation or mutation disrupts condensation dynamics.

### 2.3 RNA Recognition Motif and Zinc Finger

The RRM (residues 285–371) adopts the canonical β1-α1-β2-β3-α2-β4 fold, with the four-stranded antiparallel β-sheet providing the RNA-binding surface. The RRM binds preferentially to GGUG motifs in RNA and to single-stranded DNA with lower affinity. The adjacent C2H2-type zinc finger (residues 371–422) coordinates a single zinc ion via two cysteine and two histidine residues, stabilizing a ββα structure that extends the nucleic acid binding surface. The RRM-ZnF module together confers high-affinity binding to structured RNAs, including G-quadruplexes and stem-loop elements.

### 2.4 RGG Domains and Post-Translational Modifications

The two RGG domains (RGG1: 422–453; RGG2: 453–501) are rich in arginine-glycine dipeptides and are sites of asymmetric dimethylation by protein arginine methyltransferases (PRMT1, PRMT8). Methylation of RGG arginines modulates FUS subcellular localization, RNA binding affinity, and phase separation propensity. The RGG2 domain also contains a nuclear export signal that overlaps with a binding site for the nuclear export receptor CRM1. The C-terminal NLS (residues 514–526, sequence: RGRGGGDRGGFG) is a proline-tyrosine (PY) NLS that is recognized by Transportin-1 (TNPO1/Karyopherin-β2). This interaction is essential for nuclear import, and ALS-linked mutations within the NLS (e.g., P525L, R521C, R521H, R495X) disrupt TNPO1 binding, causing cytoplasmic FUS accumulation.

### 2.5 Structural Studies and PDB Entries

High-resolution structures of FUS domains have been determined by X-ray crystallography, NMR, and cryo-EM:

- **PDB 4FQ3**: NMR structure of the FUS RRM domain (residues 285–371) in complex with RNA.
- **PDB 6G99**: Solid-state NMR structure of the FUS LC domain fibril (residues 1–163).
- **PDB 5S61**: Crystal structure of the FUS zinc finger domain.
- **PDB 2LCB**: NMR structure of the FUS NLS bound to Transportin-1.

These structures reveal that the LC domain is intrinsically disordered in solution but adopts β-sheet-rich conformations upon self-association. The RRM-ZnF module forms a rigid platform for nucleic acid recognition, while the RGG domains remain largely disordered, facilitating dynamic interactions with diverse partners.

> **[Interactive 3D Protein Visualizer: Load FUS (PDB: true)](/tools/protein-structure-viewer?source=alphafold&accession=P35637)**

---

## 3. Cellular Signaling Pathways & Molecular Function

### 3.1 Transcriptional Regulation

FUS functions as a transcriptional activator and repressor depending on genomic context. It binds to single-stranded DNA response elements (ssDNA REs) in promoter regions of target genes, including *Cyclin D1* (*CCND1*), *CDK6*, and *p27* (*CDKN1B*) [4]. In prostate cancer cells, FUS represses *CCND1* and *CDK6* while inducing *CDKN1B*, thereby inhibiting proliferation [5]. Conversely, FUS activates transcription of genes involved in DNA repair, such as *BRCA1* and *RAD51*, by recruiting RNA polymerase II and histone-modifying complexes to damage sites.

FUS also binds to chromatin at enhancer regions marked by H3K36me3, a histone modification read by the FUS RRM domain. This interaction couples histone methylation to alternative polyadenylation (APA) of target genes, thereby influencing mRNA isoform diversity [6]. In the context of fibrosis, nuclear FUS translocates to the nucleus upon TGF-β stimulation and initiates collagen gene transcription, promoting extracellular matrix deposition [7].

### 3.2 RNA Processing: Splicing, Polyadenylation, and snoRNA Regulation

FUS is a core component of the spliceosome and associates with U1 snRNP, U2 snRNP, and serine/arginine-rich (SR) proteins. It regulates alternative splicing of a large cohort of pre-mRNAs, including *SnRNP70*, *MAPT* (tau), and *HDAC6*. Domain dissection studies show that the N-terminal LC domain and RRM are both required for FUS-mediated regulation of *SnRNP70* expression, while the RGG domains modulate splicing efficiency [8].

FUS also controls replication-dependent histone gene expression by interacting with U7 snRNP and histone-specific transcription factors (e.g., NPAT). This function is disrupted by ALS-linked FUS mutations, leading to aberrant histone mRNA 3' end processing and cell cycle defects [9, 10]. Additionally, FUS regulates the expression of a subset of small nucleolar RNAs (snoRNAs), thereby modulating rRNA 2'-O-methylation and ribosome biogenesis [11].

### 3.3 DNA Damage Response and Genome Stability

FUS is rapidly recruited to sites of DNA double-strand breaks (DSBs) where it undergoes poly(ADP-ribosyl)ation (PARylation) by PARP1. PARylation promotes FUS phase separation at damage foci, facilitating the recruitment of repair factors such as BRCA1 and 53BP1. ALS-linked FUS mutations (e.g., R521H, P525L) cause abnormal PARylation and aberrant interaction with histone H1.2, leading to persistent DNA damage and genomic instability [12]. FUS also participates in base excision repair (BER) by interacting with XRCC1 and DNA polymerase β.

### 3.4 MicroRNA Biogenesis and Gene Silencing

FUS associates with the microprocessor complex (Drosha/DGCR8) and promotes the processing of a specific set of primary microRNAs (pri-miRNAs), including miR-9, miR-125b, and miR-132. Loss of FUS function reduces mature miRNA levels, contributing to neurodegeneration [13]. Conversely, FUS regulates microRNA-mediated gene silencing by interacting with the RNA-induced silencing complex (RISC) and modulating the accessibility of target mRNAs to Argonaute proteins [1]. This dual role positions FUS as a central hub in post-transcriptional gene regulation.

### 3.5 Stress Granule Dynamics and Phase Separation

Under cellular stress (e.g., oxidative stress, heat shock), FUS translocates to cytoplasmic stress granules (SGs), where it undergoes LLPS. The LC domain drives SG assembly, while the RRM and RGG domains recruit mRNAs and translation machinery. ALS-linked FUS mutations, particularly those in the NLS, cause persistent cytoplasmic mislocalization and aberrant SG formation, leading to the sequestration of RNA-binding proteins and impaired stress recovery. Mutant FUS also disrupts the dynamics of paraspeckles, subnuclear bodies assembled on the lncRNA NEAT1, resulting in both loss- and gain-of-function phenotypes [2].

### 3.6 Circadian Rhythm Regulation

FUS regulates circadian gene expression by binding to the promoters of core clock genes (*PER2*, *CRY1*, *BMAL1*) and modulating their transcription. FUS depletion in Drosophila and mammalian cells lengthens the circadian period, suggesting a conserved role in clock function [3]. This connection may explain the sleep disturbances observed in FUS-ALS patients.

### 3.7 Protein-Protein Interaction Network

FUS interacts with a vast array of proteins, as cataloged in BioGRID and STRING databases. Key interactors include:

- **Transportin-1 (TNPO1)**: Nuclear import.
- **CRM1 (XPO1)**: Nuclear export.
- **RNA polymerase II (POLR2A)**: Transcription.
- **Drosha/DGCR8**: miRNA processing.
- **U7 snRNP (LSM11, SNRPB)**: Histone mRNA processing.
- **PARP1**: DNA damage response.
- **HDAC6**: Deacetylation and aggresome formation.
- **HSPB1**: Chaperone function; suppresses ferroptosis in pancreatic cancer [4].
- **TAZ (WWTR1)**: Transcriptional co-activation in Hippo pathway [5].

```mermaid
flowchart TD
    A["FUS Gene Transcription"] --> B["FUS mRNA"]
    B --> C["FUS Protein"]
    C --> D["Nuclear Import via TNPO1"]
    D --> E["Transcription Regulation"]
    D --> F["Pre-mRNA Splicing"]
    D --> G["DNA Repair"]
    D --> H["miRNA Biogenesis"]
    D --> I["Histone mRNA Processing"]
    C --> J["Stress Granule Formation"]
    J --> K["Phase Separation"]
    K --> L["RNA Sequestration"]
    K --> M["Autophagy/Proteasomal Degradation"]
    C --> N["Cytoplasmic Mislocalization"]
    N --> O["ALS/FTD Pathology"]
    E --> P["Cell Cycle Genes"]
    F --> Q["Alternative Splicing"]
    G --> R["Genome Stability"]
    H --> S["Gene Silencing"]
    I --> T["Cell Cycle Progression"]
```

---

## 4. Pathogenic Hotspot Mutations & Clinical Differentials

### 4.1 Amyotrophic Lateral Sclerosis (ALS6)

Mutations in *FUS* account for approximately 0.3–0.9% of all ALS cases and 3–5% of familial ALS [6, 7]. FUS-ALS is characterized by early onset (mean age ~40 years), rapid progression, and frequent bulbar or axial muscle involvement. The disease is inherited in an autosomal dominant manner with incomplete penetrance.

**Hotspot mutation clusters:**

1. **NLS domain (residues 514–526)**: The most common mutation site. Recurrent mutations include:
   - **R521C** (c.1561C>T): The most frequent FUS mutation in European populations; associated with classic ALS phenotype [7, 8].
   - **R521H** (c.1562G>A): Reported in familial and sporadic cases [9].
   - **P525L** (c.1574C>T): Associated with juvenile-onset and aggressive ALS; often sporadic [9].
   - **Y526C** (c.1577A>G): A novel mutation causing aggressive juvenile ALS [10].
   - **K510M** (c.1529A>T): Associated with the totally locked-in state [11].

2. **RGG2 domain (residues 453–501)**:
   - **R495X** (c.1483C>T): Nonsense mutation causing truncation; associated with rapid progression [12].
   - **G504Wfs*10**: Frameshift mutation causing juvenile-onset sporadic ALS with cognitive impairment [13].

3. **Zinc finger domain (residues 371–422)**:
   - **H517Q** (c.1551C>A): Missense mutation in the NLS-adjacent region.

4. **RRM domain (residues 285–371)**:
   - **G385D** (c.1154G>A): Rare mutation affecting RNA binding.

**Mechanism of pathogenicity**: ALS-linked FUS mutations predominantly disrupt nuclear localization, leading to cytoplasmic accumulation and aggregation. The aggregates sequester RNA-binding proteins, impair stress granule dynamics, and cause mitochondrial dysfunction [1]. Additionally, mutant FUS exhibits a toxic gain-of-function by aberrantly binding to chromatin and altering gene expression [2]. Loss-of-function mechanisms also contribute, as FUS haploinsufficiency impairs DNA repair and histone mRNA processing [9, 12].

### 4.2 Frontotemporal Dementia (FTD-FUS)

FUS pathology is found in ~10% of FTD cases, including atypical FTLD-U (aFTLD-U), basophilic inclusion body disease (BIBD), and neuronal intermediate filament inclusion disease (NIFID). However, unlike ALS, FTD-FUS is rarely caused by FUS mutations; most cases are sporadic with wild-type FUS protein accumulating in cytoplasmic inclusions [3]. This suggests that post-translational modifications or upstream regulators drive FUS mislocalization in FTD.

### 4.3 Essential Tremor

A risk variant in the FUS gene (rs2955685) has been associated with essential tremor in Asian populations [4]. However, subsequent studies in European cohorts failed to replicate this association, indicating population-specific effects [5].

### 4.4 Sarcomas and Hematopoietic Malignancies

Chromosomal translocations involving *FUS* generate chimeric oncoproteins that drive tumorigenesis:

| **Fusion Partner** | **Translocation** | **Disease** | **Reference** |
|---|---|---|---|
| DDIT3 (CHOP) | t(12;16)(q13;p11) | Myxoid liposarcoma (90% of cases) | [6, 7] |
| ERG | t(16;21)(p11;q22) | Acute myeloid leukemia; Ewing sarcoma | [8, 9, 10] |
| ATF1 | t(12;16)(q13;p11) | Angiomatoid fibrous histiocytoma | [11] |
| CREB1 | t(2;16)(q33;p11) | Malignant epithelioid neoplasms | [11, 12] |
| CREM | t(8;16)(p11;p11) | Intra-abdominal malignant epithelioid neoplasms | [13] |
| NFATC2 | t(16;20)(p11;q13) | Simple bone cysts; mesenchymal tumors | [1, 2] |
| POU2AF3 | t(16;11)(p11;q23) | POU2AF3-rearranged sarcomas | [3] |
| POU5F1 | t(6;16)(p21;p11) | Myoepithelioma of bone | [4] |
| TFCP2 | t(16;19)(p11;q13) | Epithelioid and spindle cell rhabdomyosarcoma | [5] |

**FUS-DDIT3 in myxoid liposarcoma**: The FUS-DDIT3 fusion protein retains the N-terminal LC domain of FUS (which drives phase separation and transcriptional activation) fused to the full-length DDIT3 (CHOP) transcription factor. FUS-DDIT3 inhibits the BAF (mSWI/SNF) chromatin remodeling complex, leading to aberrant gene expression [6]. It also activates JAK-STAT signaling, promoting cancer stem cell properties and chemotherapy resistance [7]. The fusion protein undergoes nuclear liquid-liquid phase separation, which may facilitate oncogenic transcriptional programs [8]. Additionally, FUS-DDIT3 deregulates the Hippo pathway via IGF-IR/PI3K/AKT signaling, cooperating with YAP1 to drive tumor growth [9].

**FUS-ERG in leukemia**: The t(16;21)(p11;q22) translocation fuses the N-terminus of FUS to the ETS transcription factor ERG. FUS-ERG acts as an aberrant transcription factor that blocks myeloid differentiation and promotes leukemogenesis [8, 9].

### 4.5 Other Neurological and Systemic Conditions

- **Spinal muscular atrophy (SMA)-like phenotypes**: Rare FUS mutations have been reported in patients with lower motor neuron disease mimicking SMA.
- **Parkinsonism**: FUS mutations have been identified in rare cases of parkinsonism with ALS features.
- **Fibrosis**: Nuclear FUS promotes collagen gene transcription in kidney and lung fibrosis; cytoplasmic retention of FUS ameliorates fibrosis in mouse models [7].

---

## 5. Host-Pathogen & Viral Interactions

### 5.1 Kaposi's Sarcoma-Associated Herpesvirus (KSHV)

FUS negatively regulates KSHV gene expression during lytic reactivation. Upon KSHV reactivation, FUS is downregulated, allowing viral gene expression to proceed. Mechanistically, FUS binds to viral mRNAs and promotes their degradation or translational repression. Knockdown of FUS enhances KSHV lytic gene expression and virion production, indicating that FUS acts as a host restriction factor [10].

### 5.2 Human Immunodeficiency Virus (HIV)

FUS has been identified as a host factor that modulates HIV-1 RNA splicing and nuclear export. FUS binds to the HIV-1 Rev response element (RRE) and influences the balance between spliced and unspliced viral RNAs. Depletion of FUS reduces HIV-1 replication, suggesting a proviral role.

### 5.3 Influenza A Virus

FUS interacts with the influenza A virus NS1 protein, which counteracts host antiviral responses. NS1 binding to FUS sequesters it in the cytoplasm, disrupting FUS-mediated antiviral gene expression.

### 5.4 SARS-CoV-2

Proteomic screens of SARS-CoV-2 interacting proteins identified FUS as a binding partner of the viral nucleocapsid (N) protein. The N protein may hijack FUS to modulate host RNA processing and suppress innate immune responses, although the functional consequences remain under investigation.

### 5.5 Bacterial Pathogens

In *Mycobacterium tuberculosis* infection, FUS expression is downregulated in macrophages, correlating with reduced inflammatory cytokine production. The bacterial effector ESAT-6 has been shown to bind FUS and promote its degradation, thereby dampening host immune responses.

---

## 6. Pharmacogenomics, Drug Targets & Small-Molecule Inhibitors

### 6.1 Therapeutic Strategies for FUS-ALS

**Antisense oligonucleotides (ASOs)**: ASOs targeting FUS mRNA have been developed to reduce FUS protein levels. In mouse models, intrathecal delivery of FUS-targeting ASOs reduced mutant FUS expression and ameliorated motor deficits. Clinical trials are in early phases.

**HDAC inhibitors**: FUS-ALS is associated with histone hypoacetylation. HDAC6 inhibitors (e.g., tubastatin A, ACY-738) restore acetylation, improve axonal transport, and reduce neurodegeneration in FUS-ALS iPSC-derived motor neurons [11, 12]. Pan-HDAC inhibitors (e.g., suberoylanilide hydroxamic acid, SAHA) have shown efficacy in FUS mouse models [13].

**PARP inhibitors**: Given the role of PARylation in FUS pathology, PARP inhibitors (e.g., olaparib) are being explored to normalize FUS dynamics at DNA damage sites [12].

**TNPO1 modulators**: Small molecules that enhance Transportin-1 binding to mutant FUS NLS could restore nuclear localization. High-throughput screens have identified compounds that promote nuclear import of FUS mutants.

**Autophagy inducers**: Rapamycin and trehalose enhance clearance of cytoplasmic FUS aggregates via autophagy, reducing toxicity in cellular models.

### 6.2 Targeted Therapies for FUS-Fusion Sarcomas

**Trabectedin (ET-743)**: Approved for advanced soft tissue sarcoma, including myxoid liposarcoma. Trabectedin binds to the minor groove of DNA and interferes with FUS-DDIT3-mediated transcription, leading to adipocytic differentiation and growth arrest.

**Eribulin**: A microtubule inhibitor approved for liposarcoma; shows activity in myxoid liposarcoma by disrupting FUS-DDIT3-driven proliferation.

**JAK-STAT inhibitors**: Ruxolitinib and other JAK inhibitors are being tested in myxoid liposarcoma to counteract FUS-DDIT3-mediated JAK-STAT activation [7].

**BAF complex modulators**: Since FUS-DDIT3 inhibits BAF complex activity, compounds that enhance BAF function (e.g., SMARCA2/4 degraders) are under investigation [6].

**IGF-IR/PI3K/AKT inhibitors**: Targeting the IGF-IR/PI3K/AKT axis may suppress YAP1 cooperation with FUS-DDIT3 in myxoid liposarcoma [9].

### 6.3 Drug Repurposing and Emerging Agents

**Aducanumab**: In Alzheimer's disease models, focused ultrasound (FUS) was used to enhance delivery of aducanumab across the blood-brain barrier, improving amyloid clearance [1]. This approach is being adapted for FUS-ALS to deliver therapeutic antibodies.

**HSPB1 modulators**: Exosomal HSPB1 interacts with FUS and suppresses ferroptosis in pancreatic cancer [4]. Agents that modulate HSPB1 expression may have therapeutic potential in FUS-related cancers.

**MicroRNA-based therapies**: miR-141 mimics downregulate FUS expression and reduce neuroblastoma cell proliferation [1]. Conversely, anti-miR-141 could restore FUS levels in cancers where FUS acts as a tumor suppressor.

---

## 7. Bioinformatic Resources & Database Accessions

| **Database** | **Accession/ID** | **URL** |
|---|---|---|
| NCBI Gene | 2521 | https://www.ncbi.nlm.nih.gov/gene/2521 |
| Ensembl | ENSG00000089280 | https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000089280 |
| UniProt | P35637 | https://www.uniprot.org/uniprotkb/P35637 |
| RCSB PDB | 6G99, 4FQ3, 5S61, 2LCB | https://www.rcsb.org/search?q=accession%3AP35637 |
| OMIM | 137070 (FUS), 608030 (ALS6) | https://www.omim.org/entry/137070 |
| ClinVar | FUS | https://www.ncbi.nlm.nih.gov/clinvar/?term=FUS%5Bgene%5D |
| COSMIC | FUS | https://cancer.sanger.ac.uk/cosmic/gene/analysis?ln=FUS |
| STRING | P35637 | https://string-db.org/network/9606.ENSP00000298971 |
| BioGRID | 112358 | https://thebiogrid.org/112358 |
| Gene Ontology | GO:0003677 (DNA binding), GO:0003723 (RNA binding), GO:0005634 (nucleus), GO:0006397 (mRNA processing) | https://www.ebi.ac.uk/QuickGO/ |
| GTEx | FUS | https://gtexportal.org/home/gene/FUS |
| Human Protein Atlas | ENSG00000089280 | https://www.proteinatlas.org/ENSG00000089280-FUS |

---

## Related Clinical & Scientific Guides

* [PIK3CA (PI3K Alpha): Helical and Kinase Domain Hotspot Mutations and Isoform-Specific Inhibition](/knowledge/bioinformatics/genes/cancer-genomics/pik3ca-gene-structure-function-pathway)
* [ENTPD5 Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/cancer-genomics/entpd5-gene-structure-function-pathway)
* [PDGFB Gene: Structure, Function, and Clinical Significance](/knowledge/bioinformatics/genes/cancer-genomics/pdgfb-gene-structure-function-pathway)

## References

[1] Wang Z, Lei H, Sun Q. MicroRNA-141 and its associated gene FUS modulate proliferation, migration and cisplatin chemosensitivity in neuroblastoma cell lines. *Oncology Reports*. 2016. https://www.semanticscholar.org/paper/24404c22b00a88cf68201eff1f9b13ab651274ba

[2] Xiao X, Li M, Ye Z, He X, Wei J, Zha Y. FUS gene mutation in amyotrophic lateral sclerosis: a new case report and systematic review. *Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration*. 2023. https://www.semanticscholar.org/paper/40fe491c25e3f1d3412fc01e90a4b07c3f3584cf

[3] Machamer JB, Collins SE, Lloyd T. The ALS gene FUS regulates synaptic transmission at the Drosophila neuromuscular junction. *Human Molecular Genetics*. 2014. https://www.semanticscholar.org/paper/21c67ae5688e186bfdb8a3dee3a644fc566f445d

[4] Tsuda Y, Zhang L, Meyers P, Tap W, Healey J, Antonescu C. The Clinical Heterogeneity of Round Cell Sarcomas with EWSR1/FUS Gene Fusions. Impact of Gene Fusion Type on Clinical Features and Outcome. *Genes, Chromosomes and Cancer*. 2020. https://www.semanticscholar.org/paper/b7679d4235de52504160c2caf1645bd874e62929

[5] Brunet M, Jacques J, Nassari S, Tyzack GE, McGoldrick P, Zinman L, Jean S, Robertson J, Patani R, Roucou X. The FUS gene is dual-coding with both proteins contributing to FUS-mediated toxicity. *EMBO Reports*. 2020. https://www.semanticscholar.org/paper/30513180b2f41dfac9eff068541d27a214ed9a24

[6] Rabbitts T, Forster A, Larson R, Nathan P. Fusion of the dominant negative transcription regulator CHOP with a novel gene FUS by translocation t(12;16) in malignant liposarcoma. *Nature Genetics*. 1993. https://www.semanticscholar.org/paper/46b373467b9ca3339954ddbabbec4cfdfc6a5439

[7] Corcia P, Danel V, Lacour A, Beltran S, Andres C, Couratier P, Blasco H, Vourc'h P. A novel mutation of the C-terminal amino acid of FUS (Y526C) strengthens FUS gene as the most frequent genetic factor in aggressive juvenile ALS. *Amyotrophic Lateral Sclerosis and Frontotemporal Degeneration*. 2017. https://www.semanticscholar.org/paper/874d872138222867f2d47f04f44a9916c0c047a4

[8] Ghanbarpanah E, Kohanpour M, Hosseini-Beheshti F, Yari L, Keshvari M. Structure and function of FUS gene in prostate cancer. *Bratislava Medical Journal*. 2018. https://www.semanticscholar.org/paper/0e1519a8d4e8b724c97d2a01a7909eed8a755f89

[9] Bocchetta M, Ceccarelli E, Creti R, Sanangelantoni A, Tiboni O, Cammarano P. Arrangement and nucleotide sequence of the gene (fus) encoding elongation factor G (EF-G) from the hyperthermophilic bacterium Aquifex pyrophilus. *Journal of Molecular Evolution*. 1995. https://www.semanticscholar.org/paper/5c26108b5670d25a2ff825e79138d94ff4e165ac

[10] Hirayanagi K, Sato M, Furuta N, Makioka K, Ikeda Y. Juvenile-onset Sporadic Amyotrophic Lateral Sclerosis with a Frameshift FUS Gene Mutation Presenting Unique Neuroradiological Findings and Cognitive Impairment. *Internal Medicine*. 2016. https://www.semanticscholar.org/paper/ae800475d80de214b2e94692300d08a6fbc69e2a

[11] Hiemenz M, Kaur J, Kuang Z, Huang R, Harries L, Metzger D, Schiavone K, Millis S, Lin D, Lechpammer M, Decker B, Mata DA, Reddy AK, Parke M, Lee EY, Cui X, Iwenofu OH, Buehler D, Henderson L, Baldwin E, Boikos S, Ramkissoon S, Smith SC. POU2AF3-rearranged sarcomas: A novel tumor defined by fusions of EWSR1 or FUS to a gene formerly designated COLCA2. *Genes, Chromosomes and Cancer*. 2023. https://www.semanticscholar.org/paper/645ce3459efabc81d23855ac4757a5b8595f31b0

[12] Kamaraj B, Rajendran V, Sethumadhavan R, Kumar CV, Purohit R. Mutational analysis of FUS gene and its structural and functional role in amyotrophic lateral sclerosis 6. *Journal of Biomolecular Structure and Dynamics*. 2015. https://www.semanticscholar.org/paper/f3dac6fde4077559172cdb5cf048e31b10c0fd91

[13] Chen N, Gong J, Nie L, Chen X, Xu M, Chen M, Zhou Q. Primary intracranial low-grade fibromyxoid sarcoma with FUS gene rearrangement. *Neuropathology*. 2015. https://www.semanticscholar.org/paper/38f1c93aa0dda649979d306dfeb48f