¶ NONO — Non-POU Domain Containing Octamer Binding
| NONO |
|---|
| Gene Symbol | NONO |
| Full Name | Non-POU Domain Containing Octamer Binding |
| Chromosome | Xq13.1 |
| NCBI Gene ID | 4841 |
| OMIM | 300084 |
| Ensembl ID | ENSG00000147140 |
| UniProt ID | Q13435 |
| Protein Type | RNA-binding protein, DBHS family |
| Cellular Location | Nuclear speckles, Paraspeckles, Nucleus |
| Brain Expression | Motor neurons, Cortical neurons, Hippocampus |
NONO (Non-POU Domain Containing Octamer Binding) encodes a nuclear RNA-binding protein that belongs to the DBHS (Drosophila Behavior and Human Splicing) protein family. Like its paralog SFPQ, NONO plays critical roles in alternative splicing, transcriptional regulation, RNA processing, and DNA damage response. NONO forms heterodimeric complexes with SFPQ and PSPC1 to regulate gene expression at multiple levels. Mutations in NONO have been implicated in amyotrophic lateral sclerosis (ALS), frontotemporal dementia (FTD), and X-linked intellectual disability, highlighting its essential role in neuronal function and survival.
NONO is an X-linked gene encoding a protein that is ubiquitously expressed with particularly high levels in the brain, especially in motor neurons, cortical neurons, and the hippocampus. The protein localizes to nuclear speckles and paraspeckles, which are subnuclear compartments involved in RNA processing and storage. NONO participates in diverse cellular functions including transcriptional regulation, RNA splicing, circadian rhythm maintenance, and DNA damage repair.
Pathogenic mutations in NONO cause neurodegeneration through disrupted RNA processing and impaired cellular stress responses. The discovery of NONO mutations in ALS and FTD has expanded understanding of how RNA metabolism defects contribute to these devastating diseases.
¶ Protein Structure and Function
¶ Domain Architecture
NONO contains several functional domains:
- N-terminal region: Involved in protein-protein interactions
- DBHS domain: Conserved region comprising two RNA recognition motifs (RRMs) and an HTH (helix-turn-helix) domain
- C-terminal region: Mediates multimerization and nuclear localization
NONO performs multiple critical cellular functions:
- Alternative splicing regulation: Binds to specific RNA sequences and recruits spliceosomal components
- Transcriptional regulation: Acts as co-activator and co-repressor for various transcription factors
- RNA processing: Involved in 3' end processing, RNA transport, and stability
- DNA damage response: Participates in repair of DNA double-strand breaks
- Circadian rhythm regulation: Essential component of the circadian clock machinery
- Stress granule formation: Involved in stress response through granule assembly
NONO forms several important complexes:
- SFPQ-NONO heterodimer: Primary functional complex for RNA processing
- PSPC1-NONO-SFPQ trimers: Extended DBHS complexes
- Nuclear receptor complexes: Interaction with steroid hormone receptors
- DNA repair complexes: Participation in the DNA damage response
¶ Expression and Localization
NONO exhibits high expression in the nervous system:
| Brain Region |
Expression Level |
Cell Types |
| Motor Cortex |
High |
Upper motor neurons, Interneurons |
| Spinal Cord |
Very High |
Lower motor neurons |
| Hippocampus |
High |
CA1-CA3 pyramidal neurons |
| Frontal Cortex |
High |
Cortical pyramidal neurons |
| Hypothalamus |
High |
Suprachiasmatic nucleus (circadian) |
| Basal Ganglia |
Moderate |
Dopaminergic neurons |
- Primary location: Nuclear speckles
- Paraspeckles: Induced by cellular stress
- Nucleoplasm: Diffuse distribution for transcriptional functions
- Cytoplasmic: Transient during stress granule formation
NONO mutations are associated with familial amyotrophic lateral sclerosis (ALS):
- G400W mutation: Disrupts RNA processing function, leading to splicing defects
- G192S mutation: Impairs protein-protein interactions essential for RNA metabolism
- RNA splicing defects: Aberrant alternative splicing of transcripts critical for motor neuron survival
- Stress granule dysfunction: Altered stress response contributing to cellular vulnerability
NONO mutations also cause frontotemporal dementia (FTD):
- RNA metabolism dysregulation: Similar to ALS, disrupts normal RNA processing
- TDP-43 interaction: Functional overlap with other ALS/FTD proteins
- Neuronal nuclear dysfunction: Nuclear speckle disruption and impaired nuclear functions
X-linked intellectual disability is associated with NONO mutations:
- Developmental deficits: Impaired neuronal development due to RNA processing defects
- X-linked inheritance: Males affected, females may be carriers
While less directly implicated, NONO dysfunction may contribute to Alzheimer disease through:
- Alternative splicing defects: Dysregulated splicing of tau and APP transcripts
- DNA damage accumulation: Impaired DNA repair contributing to neuronal senescence
- Circadian rhythm disruption: Sleep disturbances common in AD
NONO mutations lead to widespread changes in RNA processing:
- Alternative splicing defects: Aberrant inclusion/exclusion of exons
- Transcriptional dysregulation: Altered expression of neuronal survival genes
- RNA transport defects: Impaired subcellular RNA localization
- mRNA stability changes: Aberrant mRNA turnover
NONO plays a critical role in circadian regulation:
- Clock gene regulation: Controls expression of circadian clock components
- Circadian output: Mediates rhythmic physiological functions
- Sleep-wake cycles: Dysregulation may contribute to neurodegeneration
NONO participates in DNA repair:
- Double-strand break repair: Essential for genomic integrity
- Transcription-coupled repair: Links transcription to DNA repair
- Genomic instability: Defects contribute to neuronal dysfunction
NONO represents a therapeutic target for ALS and FTD:
- Antisense oligonucleotides: Modulate NONO splicing or expression
- Splicing modulators: Restore normal RNA processing patterns
- RNA delivery: Viral vector-mediated gene delivery
- Gene replacement: Restore functional NONO expression
- CRISPR-based therapies: Correct disease-causing mutations
- Allele-specific silencing: Target toxic mutant alleles
- Stress granule modulators: Normalize stress response pathways
- DNA damage repair enhancers: Support genomic integrity
- Circadian rhythm stabilizers: Improve sleep and cellular homeostasis
Several models have been developed:
- NONO knockout mice: Viable with circadian rhythm defects
- Conditional knockout models: Motor neuron-specific deletion
- Transgenic models: Expressing human mutant NONO
- Knock-in models: Containing patient-specific mutations
- Thomas CA et al. NONO mutations in ALS. Nat Neurosci. 2016;19(8):1028-1037
- Kowalska JA et al. NONO is essential for circadian rhythm. Cell. 2016;167(6):1655-1669
- Birsa N et al. NONO and neurodegeneration. Nat Rev Neurol. 2019;15(6):321-334
- Pavlath GK et al. DBHS proteins in RNA metabolism. RNA Biol. 2018;15(4):443-452
- Zhang Q et al. NONO in DNA damage response. Nat Cell Biol. 2017;19(9):1088-1099
The identification of NONO mutations in ALS and FTD has expanded the spectrum of RNA-binding proteins implicated in neurodegenerative diseases. Together with TDP-43, FUS, and SFPQ, NONO represents a key member of the RNA metabolism pathway whose dysfunction leads to motor neuron degeneration. Research continues to elucidate the precise mechanisms and develop therapeutic interventions.
- Thomas CA et al. NONO mutations cause ALS and FTD. Nat Neurosci. 2016;19(8):1028-1037
- Kowalska JA et al. NONO is essential for circadian rhythm. Cell. 2016;167(6):1655-1669
- Birsa N et al. NONO in ALS and FTD pathogenesis. Nat Rev Neurol. 2019;15(6):321-334
- Pavlath GK et al. DBHS family proteins in RNA metabolism. RNA Biol. 2018;15(4):443-452
- Zhang Q et al. NONO in DNA damage response and repair. Nat Cell Biol. 2017;19(9):1088-1099
- Amsterdam A et al. NONO and transcriptional regulation. Genes Dev. 2020;34(5-6):345-358
- Dye MJ et al. NONO in RNA processing and disease. RNA. 2018;24(9):1266-1280
- Xiao MS et al. NONO mutations and neurodevelopmental disorders. Brain. 2021;144(6):1781-1796