ercc3-protein

ERCC3 (Excision Repair Cross-Complementation Group 3) Protein

Protein Information

<div class="infobox infobox-protein">
| Property | Value |
|---------|-------|
| Protein Name | ERCC3 (XPB, TFIIH p89) |
| Gene | [ERCC3](/genes/ercc3) |
| UniProt ID | [P18080](https://www.uniprot.org/uniprot/P18080) |
| Molecular Weight | ~89 kDa (782 amino acids) |
| Subcellular Localization | Nucleus |
| Protein Family | DEAH-box helicase family |
| Protein Class | ATP-dependent DNA helicase |
| Brain Expression | High in neurons, especially hippocampus and cortex |
</div>

Overview

ERCC3 (also known as XPB, XPD, TFIIH p89, or general transcription factor IIH subunit) is a critical DNA helicase and ATP-dependent 3'-5' translocase that functions as a core component of the TFIIH (Transcription Factor II H) complex. This protein plays dual essential roles in both RNA polymerase II transcription initiation and nucleotide excision repair (NER), making it fundamental to genomic stability in post-mitotic neurons. ERCC3 is encoded by the [ERCC3](/genes/ercc3) gene on chromosome 19q13.2, and mutations in this gene cause severe human diseases including xeroderma pigmentosum (XP) and Cockayne syndrome, highlighting its critical importance in maintaining neuronal health. [@egner2018]

Normal Cellular Function

Role in TFIIH Complex

ERCC3 forms the core of the TFIIH complex, which consists of seven subunits (XPB, XPD, p62, p52, p44, p34, and p8/GTF2H4). Within this complex, ERCC3/XPB performs essential mechanical functions:

ERCC3 (Excision Repair Cross-Complementation Group 3) Protein

Protein Information

<div class="infobox infobox-protein">
| Property | Value |
|---------|-------|
| Protein Name | ERCC3 (XPB, TFIIH p89) |
| Gene | [ERCC3](/genes/ercc3) |
| UniProt ID | [P18080](https://www.uniprot.org/uniprot/P18080) |
| Molecular Weight | ~89 kDa (782 amino acids) |
| Subcellular Localization | Nucleus |
| Protein Family | DEAH-box helicase family |
| Protein Class | ATP-dependent DNA helicase |
| Brain Expression | High in neurons, especially hippocampus and cortex |
</div>

Overview

ERCC3 (also known as XPB, XPD, TFIIH p89, or general transcription factor IIH subunit) is a critical DNA helicase and ATP-dependent 3'-5' translocase that functions as a core component of the TFIIH (Transcription Factor II H) complex. This protein plays dual essential roles in both RNA polymerase II transcription initiation and nucleotide excision repair (NER), making it fundamental to genomic stability in post-mitotic neurons. ERCC3 is encoded by the [ERCC3](/genes/ercc3) gene on chromosome 19q13.2, and mutations in this gene cause severe human diseases including xeroderma pigmentosum (XP) and Cockayne syndrome, highlighting its critical importance in maintaining neuronal health. [@egner2018]

Normal Cellular Function

Role in TFIIH Complex

ERCC3 forms the core of the TFIIH complex, which consists of seven subunits (XPB, XPD, p62, p52, p44, p34, and p8/GTF2H4). Within this complex, ERCC3/XPB performs essential mechanical functions:

The TFIIH complex bridges RNA polymerase II with the promoter, and its helicase activity is essential for promoter clearance and transcription elongation. [@coin2007]

Nucleotide Excision Repair (NER)

ERCC3 is essential for the NER pathway, which removes bulky DNA lesions including:

• UV-induced lesions: Cyclobutane pyrimidine dimers (CPDs), 6-4 photoproducts
• Chemical adducts: Benzo[a]pyrene diol epoxide (BPDE) adducts
• Oxidative damage: Certain oxidized bases
• Crosslinks: DNA interstrand crosslinks

ERCC3's helicase activity is crucial for the unwinding step that allows excision machinery to access the damaged region. [@scharer2015]

Transcription-Coupled NER (TC-NER)

Beyond global genome NER (GG-NER), ERCC3 is critical for transcription-coupled NER (TC-NER), which specifically removes lesions from actively transcribed DNA strands. This pathway is particularly important in neurons, which are post-mitotic and cannot undergo DNA replication to bypass lesions.

When RNA polymerase II encounters a blocking lesion, it stalls and recruits the TC-NER machinery including CSA and CSB proteins. TFIIH (with ERCC3) is then recruited to unwind the DNA and facilitate repair. [@mol2018]

Role in Alzheimer's Disease

DNA Damage Accumulation

Neurons in AD brains accumulate significant DNA damage, including:

• 8-oxoguanine (8-oxoG) lesions from oxidative stress
• Single-strand breaks from various sources
• Double-strand breaks in vulnerable regions
• Telomere attrition

TFIIH Dysregulation in AD

Symeonides et al. (2021) investigated TFIIH subunit expression in AD brains and found:

• Reduced ERCC3 protein levels in hippocampus and prefrontal cortex
• Decreased TFIIH complex integrity
• Correlation between ERCC3 reduction and cognitive decline
• Association with tau pathology burden

Choi et al. (2020) demonstrated that:

• Aβ oligomers downregulate ERCC3 expression
• ERCC3 reduction increases DNA damage sensitivity
• ERCC3 overexpression protects against Aβ toxicity
• ERCC3 is required for proper neuronal stress response

Therapeutic Implications

Strategies targeting ERCC3 and NER in AD include:

Role in Parkinson's Disease

Oxidative Stress and DNA Damage

PD is characterized by significant oxidative stress in dopaminergic neurons of the substantia nigra. This oxidative environment causes:

• 8-oxoG accumulation in nuclear and mitochondrial DNA
• Strand breaks from reactive oxygen species
• Mitochondrial DNA deletions
• Accumulated damage over time

• Have high metabolic demands
• Generate significant ROS from dopamine metabolism
• Have limited capacity for DNA repair compared to proliferating cells
• Cannot be replaced through cell division [@nouspikel2007]

ERCC3 in PD Models

Lee et al. (2021) investigated ERCC3 in PD models:

• ERCC3 expression reduced in substantia nigra of PD brains
• MPTP treatment decreases ERCC3 in dopaminergic neurons
• ERCC3 knockdown increases sensitivity to mitochondrial toxins
• Overexpression protects against 6-OHDA toxicity

Mitochondrial DNA Repair

ERCC3 is involved in repair of mitochondrial DNA (mtDNA), though the exact mechanisms are still being characterized. Given the central role of mitochondrial dysfunction in PD, maintaining mtDNA integrity through ERCC3-mediated repair is critical for neuronal survival.

Role in Other Neurodegenerative Diseases

Xeroderma Pigmentosum (XP)

ERCC3 mutations cause XP complementation group B (XP-B), characterized by:

• Extreme photosensitivity
• 10,000-fold increased risk of skin cancer
• Progressive neurodegeneration in some patients
• Cockayne syndrome features in severe cases

• Intellectual disability
• Ataxia
• Sensorineural hearing loss
• Premature aging

Cockayne Syndrome (CS)

While primarily caused by ERCC8 (CSA) and ERCC6 (CSB) mutations, ERCC3-related TFIIH deficiencies can produce CS-like phenotypes:

• Progeroid features
• Severe neurological impairment
• Growth failure

• Rapid aging

Huntington's Disease

DNA repair deficits are increasingly recognized in HD:

• Mutant huntingtin impairs NER
• ERCC3 expression altered in HD models
• DNA damage accumulates in striatal neurons
• Repair pathway enhancement is therapeutic target

Amyotrophic Lateral Sclerosis (ALS)

NER and transcription-coupled repair are impaired in ALS:

• ERCC3 levels altered in motor neurons
• Increased DNA damage in sporadic ALS
• TDP-43 pathology affects TFIIH function
• Enhanced DNA repair is protective

DNA Repair and Aging

The aging brain shows progressive decline in DNA repair capacity:

Robinson et al. (2020) demonstrated that:

• DNA damage accumulates in aging neurons
• Repair capacity decreases with age
• Accumulated damage correlates with cognitive decline
• Enhanced DNA repair extends neuronal health

Structure-Function Relationships

ERCC3 contains several functional domains:

Key structural features:

• Two RecA-like helicase domains (D1 and D2)
• ATP-binding pocket in D1
• DNA-binding channel formed between domains
• Flexible C-terminal region for regulatory interactions

Therapeutic Targeting

Small Molecule Approaches

Gene Therapy

• AAV-mediated ERCC3 delivery to neurons
• CRISPR-based correction of pathogenic mutations
• Promoter engineering for increased expression

Challenges

Key Publications

Related Pathways

• [Nucleotide Excision Repair](/mechanisms/nucleotide-excision-repair)
• [DNA Repair in Neurodegeneration](/mechanisms/dna-repair-neurodegeneration)
• [Transcription](/mechanisms/transcription)
• [Oxidative Stress](/mechanisms/oxidative-stress)
• [Aging and Neurodegeneration](/mechanisms/aging-neurodegeneration)

See Also

• [ERCC3 Gene](/genes/ercc3)
• [TFIIH Complex](/proteins/tfiiH-complex)
• [XPA Protein](/proteins/xpa-protein)
• [XPC Protein](/proteins/xpc-protein)
• [DNA Repair](/mechanisms/dna-repair-neurodegeneration)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Xeroderma Pigmentosum](/diseases/xeroderma-pigmentosum)

External Links

• [UniProt: P18080](https://www.uniprot.org/uniprot/P18080)
• [NCBI Gene: ERCC3](https://www.ncbi.nlm.nih.gov/gene/2065)
• [PDB: 1XW6](https://www.rcsb.org/structure/1XW6)
• [GeneCards: ERCC3](https://www.genecards.org/cgi-bin/carddisp.pl?gene=ERCC3)
• [Allen Brain Atlas - Gene Expression](https://human.brain-map.org/microarray/search/show?search_term=ERCC3)