XPF Gene

XPF Gene

Overview

XPF Gene

Overview

<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

XPF-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

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

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

Neurodegeneration

Reduced XPF function has been implicated in age-related neurodegenerative diseases through multiple mechanisms[@kelley2011]:

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

Interactions 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

Unresolved 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

External 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

Pathway Diagram

The following diagram shows the key molecular relationships involving XPF Gene discovered through SciDEX knowledge graph analysis: