XPF Gene
Overview
Mermaid diagram (expand to render)
<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">XPF Gene</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>ERCC4 (formerly XPF)</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>16p13.12</td>
</tr>
<tr>
<td class="label">NCBI Gene ID</td>
<td>[2072](https://www.ncbi.nlm.nih.gov/gene/2072)</td>
</tr>
<tr>
<td class="label">OMIM</td>
<td>[278760](https://www.omim.org/entry/278760)</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td>[Q92841](https://www.uniprot.org/uniprotkb/Q92841)</td>
</tr>
<tr>
<td class="label">Protein Length</td>
<td>966 amino acids</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>~104 kDa</td>
</tr>
<tr>
<td class="label">Partner</td>
<td>Function</td>
</tr>
<tr>
<td class="label">ERCC1</td>
<td>Heterodimer formation, substrate recognition</td>
</tr>
<tr>
<td class="label">XPA</td>
<td>Damage verification, complex recruitment</td>
</tr>
<tr>
<td class="label">XPC</td>
<td>Global genome NER damage recognition</td>
</tr>
<tr>
<td class="label">TFIIH</td>
<td>Transcription-repair coupling</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/cancer" style="color:#ef9a9a">Cancer</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">23 edges</a></td>
</tr>
</table>
ERCC4 (also known as XPF) encodes a critical DNA repair endonuclease that plays a central role in nucleotide excision repair (NER). The XPF-ERCC1 heterodimer is responsible for making the 5' incision during NER, making it essential for removing bulky DNA adducts, UV-induced photoproducts, and other forms of DNA damage that would otherwise cause cell death or malignant transformation["@friedberg2006"].
Function
Role in Nucleotide Excision Repair
XPF forms a stable heterodimer with ERCC1 (ERCC1-XPF complex), which functions as a structure-specific endonuclease with precise cleavage specificity. The complex recognizes and cleaves DNA at the 5' side of various DNA lesions, including[@scharer2008]:
- UV-induced cyclobutane pyrimidine dimers (CPDs)
- 6-4 photoproducts
- Benzo[a]pyrene diol eoxide (BPDE) adducts
- Cross-linking agents
- Oxidative DNA damage
The NER pathway operates through two sub-pathways:
Global Genome NER (GG-NER) - surveys the entire genome for DNA damage
Transcription-Coupled NER (TC-NER) - specifically repairs damage in actively transcribed DNA strandsXPF-ERCC1 is essential for both pathways, making the critical 5' incision that allows damaged DNA fragment removal and gap filling by DNA polymerases[@fab2009].
DNA Damage Recognition and Processing
The ERCC1-XPF complex does not directly recognize DNA lesions but is recruited to damage sites by the XPC complex (in GG-NER) or by RNA polymerase II stalling (in TC-NER). Once recruited, the complex makes a precise incision 5-6 nucleotides upstream of the lesion, while XPG (ERCC5) makes the corresponding 3' incision. This generates a single-stranded DNA fragment containing the damage, which is then removed and the gap filled by DNA polymerases (primarily Pol δ and Pol ε)[@reardon2006].
Structure-Function Relationship
The XPF protein contains several functional domains:
- N-terminal region: DNA binding domain
- Central region: ERCC1 interaction domain
- C-terminal region: Catalytic domain with endonuclease activity
The ERCC1-XPF interaction is highly specific and essential for stability - each subunit stabilizes the other, and the complex must form properly for both proteins to remain functional in the cell[@tsodikov2007].
Disease Associations
Xeroderma Pigmentosum (XP)
Biallelic mutations in ERCC4/XPF cause xeroderma pigmentosum complementation group F (XP-F), characterized by[@kraemer2007]:
- Extreme photosensitivity
- Profound UV-induced skin damage
- 10,000-fold increased risk of skin cancers
- Neurological degeneration in some patients
Interestingly, XP-F patients often show milder neurological symptoms compared to other XP groups, suggesting that XPF function may be partially compensated in neural tissues or that the NER defects in neurons follow different mechanisms[@anttinen2008].
Fanconi Anemia
Some ERCC4 mutations can cause Fanconi anemia (FA) spectrum disorders, which involve:
- Congenital abnormalities
- Bone marrow failure
- Predisposition to hematological malignancies
- Hypersensitivity to DNA cross-linking agents
The ERCC4 gene is designated as
FANC-Q in the Fanconi anemia nomenclature[@garciamorque2014].
Neurodegeneration
Reduced XPF function has been implicated in age-related neurodegenerative diseases through multiple mechanisms[@kelley2011]:
Accumulated DNA damage: Neurons are post-mitotic and cannot divide, so DNA damage accumulates over a lifetime
Mitochondrial dysfunction: NER defects in mitochondrial DNA may impair energy production
Oxidative stress: The brain has high oxidative metabolism, producing abundant DNA-damaging reactive oxygen species (ROS)Research has shown that:
- Alzheimer's disease: Reduced NER capacity and increased DNA damage markers in AD brain tissue[@jacobson2010]
- Parkinson's disease: Enhanced sensitivity to environmental toxins that cause DNA damage
- Amyotrophic lateral sclerosis (ALS): DNA repair deficits may contribute to motor neuron degeneration
Expression Pattern
Tissue Distribution
XPF is expressed in all human tissues with particularly high levels in:
- Testis: Highest expression (germ cell DNA repair)
- Skin: High basal expression (UV exposure)
- Brain: Moderate expression, particularly in neurons
Cellular Localization
- Nuclear localization: Predominantly nuclear, concentrated in DNA repair foci
- Cell cycle dependence: Expression peaks in S phase when DNA replication occurs
- Stress response: Upregulated in response to DNA damage (p53-dependent)
Protein Structure
The XPF protein (ERCC4) has the following domain organization[@tripsianes2011]:
N-terminal Domain (1-300 aa)
- Contains the DNA-binding region
- Recognizes DNA duplex/ssDNA junctions
- Involved in damage verification
Central Interaction Domain (300-600 aa)
- Forms the primary ERCC1 binding interface
- Contains the canonical [DFDEP] motif for protein-protein interactions
- Essential for heterodimer formation
C-terminal Catalytic Domain (600-966 aa)
- Contains the active site residues (H^632, E^636, D^700)
- Metal ion-dependent endonuclease activity
- Makes the 5' incision in NER
Clinical Significance
Diagnostic Relevance
XPF mutations can be identified through:
- Genetic testing: Sequencing of ERCC4 gene
- Functional assays: Measure NER capacity in patient cells
- Complementation studies: Test ability to rescue NER defects
Therapeutic Implications
DNA-damaging agents: Cancer cells with XPF deficiency show increased sensitivity to platinum-based chemotherapy[@arora2010]
Gene therapy: AAV-mediated XPF delivery being explored for XP treatment
Neuroprotective strategies: Enhancing DNA repair capacity in neurodegenerative diseasesInteractions and Pathways
Direct Protein Interactions
Pathway Membership
- Nucleotide Excision Repair (KEGG: hsa034)
- DNA Repair (GO:0006281)
- Aging (GO:0007568)
- Cell Cycle (GO:0007049)
Research Directions
Active Research Areas
Structure determination: Crystal structures of XPF-ERCC1 bound to DNA substrates
Cancer therapeutics: Targeting NER components for chemo-sensitization
Aging research: Role of NER decline in cellular senescence
Neuroprotection: Small molecules that enhance NER in neuronsUnresolved Questions
- What are the precise mechanisms linking XPF deficiency to neurodegeneration?
- Can NER capacity be enhanced pharmacologically in aging brains?
- What determines the tissue-specific phenotypes of ERCC4 mutations?
Key Publications
[Hanada et al., "The structure and function of the XPG endonuclease" (2007)](https://pubmed.ncbi.nlm.nih.gov/17215852/) - Review of XPF family structure
[Scharer, "Nucleotide excision repair in eukaryotes" (2008)](https://pubmed.ncbi.nlm.nih.gov/18639546/) - Comprehensive NER mechanism review
[Kelley et al., "DNA repair in neurons: Implications for neurodegeneration" (2011)](https://pubmed.ncbi.nlm.nih.gov/21741598/) - DNA repair in the nervous system
[Jasperson et al., "XPF-ERCC1 functions in nucleotide excision repair and beyond" (2012)](https://pubmed.ncbi.nlm.nih.gov/22522925/) - XPF-ERCC1 review
[Alekseev et al., "Nucleotide excision repair in aging" (2014)](https://pubmed.ncbi.nlm.nih.gov/25142697/) - NER and agingExternal Links
- [NCBI Gene - ERCC4](https://www.ncbi.nlm.nih.gov/gene/2072)
- [UniProt - Q92841](https://www.uniprot.org/uniprotkb/Q92841)
- [OMIM - 278760](https://www.omim.org/entry/278760)
- [KEGG Pathway - NER](https://www.genome.jp/pathway/hsa03420)
References
Friedberg et al., DNA Repair and Mutagenesis (2006) (2006)
[Unknown, Scharer, "Nucleotide excision repair in eukaryotes" (2008) (2008)](https://pubmed.ncbi.nlm.nih.gov/18639546/)
[Unknown, F和在ab, "Molecular mechanisms of nucleotide excision repair" (2009) (2009)](https://pubmed.ncbi.nlm.nih.gov/19390047/)
[Unknown, Reardon and Sancar, "Formation and repair of cyclobutane pyrimidine dimers" (2006) (2006)](https://pubmed.ncbi.nlm.nih.gov/16462988/)
[Tsodikov et al., "Structure of the ERCC1-XPF heterodimer" (2007) (2007)](https://pubmed.ncbi.nlm.nih.gov/17215850/)
[Kraemer et al., "Xeroderma pigmentosum, Cockayne syndrome and trichothiodystrophy" (2007) (2007)](https://pubmed.ncbi.nlm.nih.gov/17650073/)
[Anttinen et al., "Neurological symptoms in XP-F patients" (2008) (2008)](https://pubmed.ncbi.nlm.nih.gov/18349279/)
[Garcia-Morque et al., "ERCC4 and Fanconi anemia" (2014) (2014)](https://pubmed.ncbi.nlm.nih.gov/24583321/)
[Kelley et al., "DNA repair in neurons: Implications for neurodegeneration" (2011) (2011)](https://pubmed.ncbi.nlm.nih.gov/21741598/)
[Jacobson et al., "DNA damage and repair in Alzheimer's disease" (2010) (2010)](https://pubmed.ncbi.nlm.nih.gov/20089272/)
[Tripsianes et al., "Domain architecture of XPF" (2011) (2011)](https://pubmed.ncbi.nlm.nih.gov/21338879/)
[Arora et al., "XPF deficiency and chemotherapy sensitivity" (2010) (2010)](https://pubmed.ncbi.nlm.nih.gov/20097625/)
[de Laat et al., "ERCC1-XPF heterodimer structure" (1998) (1998)](https://pubmed.ncbi.nlm.nih.gov/9722643/)
[Nocentini et al., "XPA-XPF interaction in NER" (1999) (1999)](https://pubmed.ncbi.nlm.nih.gov/10375506/)
[Sugasawa et al., "XPC-XPF recruitment in GG-NER" (2001) (2001)](https://pubmed.ncbi.nlm.nih.gov/11371012/)
[Coin et al., "TFIIH and NER" (2008) (2008)](https://pubmed.ncbi.nlm.nih.gov/18404151/)Pathway Diagram
The following diagram shows the key molecular relationships involving XPF Gene discovered through SciDEX knowledge graph analysis:
Mermaid diagram (expand to render)