| RPA3 |
|---|
| Full Name | Replication Protein A3 |
| Symbol | RPA3 |
| Chromosomal Location | 7q32.3 |
| NCBI Gene ID | [6731](https://www.ncbi.nlm.nih.gov/gene/6731) |
| Ensembl ID | ENSG00000186871 |
| UniProt ID | [P35274](https://www.uniprot.org/uniprot/P35274) |
| Associated Diseases | [Alzheimer's Disease](/diseases/alzheimers-disease), [Parkinson's Disease](/diseases/parkinsons-disease) |
RPA3 (Replication Protein A3) is a subunit of the heterotrimeric Replication Protein A complex (RPA), the major single-stranded DNA (ssDNA)-binding protein in eukaryotic cells. RPA plays essential roles in DNA replication, repair, recombination, and the DNA damage response. While RPA3 is the smallest subunit, it is essential for complex stability and function. Recent research has revealed important connections between RPA dysfunction and neurodegenerative diseases, particularly Alzheimer's disease (AD) and Parkinson's disease (PD), where DNA damage accumulation and impaired DNA repair are key pathological features [1][2].
This page covers the gene's normal molecular function, structure, disease associations, expression patterns, and implications for neurodegeneration research.
RPA is a heterotrimeric complex composed of:
- RPA1 (RPA70): 70 kDa subunit - contains multiple DNA-binding domains (DBDs) and protein interaction domains
- RPA2 (RPA32): 32 kDa subunit - phosphorylated in response to DNA damage, regulates protein interactions
- RPA3 (RPA14): 14 kDa subunit - smallest subunit, essential for complex assembly and stability
The RPA complex binds with high affinity to ssDNA, forming a protective shield that prevents:
- Secondary structure formation
- Nucleolytic degradation
- Unwanted recombination
RPA is essential for DNA replication:
¶ Origin Recognition and Activation
- RPA helps unwind DNA at replication origins
- Interacts with origin recognition complex (ORC)
- Loads replication factors onto single-stranded DNA
- Facilitates minichromosome maintenance (MCM) complex loading
¶ Leading and Lagging Strand Synthesis
- Provides ssDNA template protection
- Interacts with DNA polymerases (Pol α, δ, ε)
- Coordinates primer synthesis and extension
- Regulates replication fork progression
- Stalls forks at DNA damage sites
- Activates checkpoint signaling
- Prevents fork collapse
- Facilitates fork restart
RPA participates in multiple DNA repair pathways:
- Initial damage recognition
- Helicase loading (XPA, XPF)
- Gap filling coordination
- Single-strand break recognition
- Gap filling coordination
- DNA ligase recruitment
- Resection monitoring
- RAD51 filament formation regulation
- Strand invasion assistance
- Mismatch detection coordination
- Strand discrimination
- Excision and resynthesis
RPA is a central sensor of DNA damage:
- Binds directly to ssDNA generated by damage
- Recognizes stalled replication forks
- Detects gaps and breaks
- Activates ATR/ATRIP kinase pathway
- Phosphorylates CHK1 and CHK2
- Coordinates cell cycle arrest
- Recruits repair proteins to damage sites
- Modulates chromatin accessibility
- Coordinates repair pathway choice
¶ Telomere Maintenance
RPA functions at telomeres:
- Protects telomeric ssDNA
- Facilitates telomere replication
- Prevents telomere dysfunction
- Works with shelterin complex
RPA3 (14 kDa) contains:
- N-terminal domain: Essential for complex formation
- Central region: Interacts with RPA1 and RPA2
- C-terminal region: Dimerization interface
The protein forms a tight heterotrimer with RPA1 and RPA2, requiring all three subunits for stable complex formation.
RPA3 is subject to:
- Phosphorylation: By ATM/ATR/DNA-PK in response to damage
- Acetylation: Regulates protein-protein interactions
- SUMOylation: Affects subcellular localization
- Ubiquitination: Targets for degradation
RPA3 connects to AD through multiple mechanisms:
AD neurons show:
- Elevated levels of oxidative DNA damage
- Accumulation of DNA double-strand breaks
- Impaired repair of neuronal DNA damage
- Telomere shortening
- Decreased RPA focus formation in AD brains
- Impaired ATR signaling
- Reduced CHK1 activation
- Compromised checkpoint function
- Aβ peptides can cause DNA damage directly
- RPA recruitment is impaired in Aβ-treated cells
- Amyloid plaques are surrounded by DNA damage
- Phosphorylated tau affects DNA repair proteins
- RPA mislocalization in tauopathy neurons
- Synaptic DNA damage accumulation
RPA3 involvement in PD:
- High metabolic demands = high DNA damage
- Limited DNA repair capacity
- Mitochondrial dysfunction increases damage
- Alpha-synuclein affects DNA repair
- mtDNA damage accumulates in PD
- RPA may be involved in mtDNA repair
- PINK1/Parkin pathway intersects with DNA damage response
- LRRK2 mutations increase DNA damage sensitivity
- RPA phosphorylation affected by LRRK2
- G2019S mutation impairs checkpoint recovery
- DNA damage is a consistent finding
- RPA foci form in motor neurons
- TDP-43 pathology affects DNA repair
- CAG repeat expansions cause DNA damage
- RPA recruitment is impaired
- DNA repair is a therapeutic target
- ATM deficiency causes neurodegeneration
- RPA phosphorylation is ATM-dependent
- Combined DNA repair and neurodegenerative phenotype
RPA3 is expressed in:
- Brain: Neurons and glia
- Proliferating cells: High expression in dividing cells
- Post-mitotic neurons: Lower but essential levels
- Muscle: Moderate expression
- High in stem cells and progenitors
- Moderate in most somatic cells
- Essential in neurons despite lower levels
RPA3 expression is regulated by:
- Cell cycle factors
- DNA damage signaling
- Developmental programs
- Tissue-specific transcription
In neurodegeneration:
- Reduced RPA focus formation
- Delayed recruitment of repair proteins
- Prolonged checkpoint activation
- Incomplete repair
DNA repair requires chromatin remodeling:
- Histone modifications altered in AD/PD
- Heterochromatin loss increases vulnerability
- RPA-chromatin interactions impaired
Neuronal metabolism affects RPA:
- Oxidative stress inhibits RPA function
- Mitochondrial dysfunction increases damage
- NAD+ depletion affects repair
Pathogenic proteins affect DNA repair:
- Tau affects RPA recruitment
- α-Synuclein may sequester repair proteins
- TDP-43 mislocalization impacts function
Targeting RPA and DNA repair:
- PARP inhibitors (under investigation)
- ATR inhibitors (in cancer, potential for neurodegeneration)
- Checkpoint kinase inhibitors
- Increase DNA repair capacity
- Express DNA repair proteins
- Protect against damage
- Exercise enhances DNA repair
- Antioxidants reduce damage
- Caloric restriction effects