Fused in Sarcoma is a protein encoded by the C9orf72 gene. This page describes its structure, normal nervous system function, role in neurodegenerative disease, and potential as a therapeutic target.
Fused in Sarcoma (FUS) is a DNA/RNA-binding protein that plays critical roles in RNA splicing, transcription, and DNA repair. Mutations in the FUS gene are causally linked to amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD).
| Attribute |
Details |
| Gene Symbol |
FUS |
| Chromosomal Location |
16p11.2 |
| Protein Name |
Fused in Sarcoma |
| Molecular Weight |
~56 kDa |
| Primary Function |
RNA/DNA binding, RNA splicing, transcription regulation |
The FUS protein contains multiple functional domains:
- N-terminal Low-Complexity Domain - Prone to liquid-liquid phase separation, forms stress granules
- RNA Recognition Motif (RRM) - Binds RNA molecules
- Zinc Finger Domain - DNA binding capability
- C-terminal Proline-rich Region - Protein-protein interactions
¶ Phase Separation and Stress Granules
FUS participates in stress granule formation through its low-complexity domain. In disease:
- Mutations in FUS lead to aberrant phase separation
- Dysregulated stress granule dynamics cause toxic aggregation
- Impaired RNA metabolism due to sequestered RNA-binding proteins
- FUS mutations impair nuclear import via importin-α/β pathway
- Cytoplasmic FUS accumulation is a hallmark of FUS-ALS
- Nuclear loss-of-function disrupts RNA processing
FUS is involved in DNA repair mechanisms:
- Associates with DNA double-strand break sites
- Facilitates homologous recombination
- Loss of DNA repair function contributes to neurodegeneration
FUS mutations account for ~5% of familial ALS cases:
- Onset typically earlier than SOD1/ C9orf72 ALS (median age 40-50)
- Predominant bulbar onset in some mutations
- Rapid progression in certain variants
- FUS-positive inclusions in motor neurons
- FUS pathology in ~10% of FTD cases
- Often co-occurs with ALS
- Behavioral variant FTD presentation
- Language variant FTD (especially non-fluent variant)
- TDP-43 (TARDBP) - Co-pathology in ALS/FTD
- hnRNPs - RNA processing partners
- Importin-α/β - Nuclear import machinery
- EZH2 - Transcriptional regulation
- DNA repair proteins - ATM, BRCA1
- Nuclear Import Modulators - Improve FUS nuclear localization
- Phase Separation Modulators - Normalize stress granule dynamics
- RNA Splicing Modulators - Restore proper RNA processing
- DNA Repair Enhancers - Support genome stability
- Antisense oligonucleotides targeting FUS mRNA
- Small molecules promoting nuclear import
- Gene therapy approaches
- Protein degradation strategies (autophagy, UPS)
- TDP-43 - Co-aggregates with FUS
- TREM2 - Microglial activation in neurodegeneration
- SOD1 - Classic ALS protein