PARP4 — Poly(ADP-Ribose) Polymerase 4

PARP4 — Poly(ADP-Ribose) Polymerase 4

Overview

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">PARP4 — Poly(ADP-Ribose) Polymerase 4</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>PARP4</td>
</tr>
<tr>
<td class="label">Protein</td>
<td>Poly(ADP-ribose) polymerase 4 (Vault PARP, vPARP)</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>13q12.12</td>
</tr>
<tr>
<td class="label">NCBI Gene ID</td>
<td>8548</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q9UKK3</td>
</tr>
<tr>
<td class="label">Aliases</td>
<td>PARP4, ARTD4, vPARP</td>
</tr>
<tr>
<td class="label">Domain</td>
<td>Function</td>
</tr>
<tr>
<td class="label">N-terminal region</td>
<td>Protein-protein interactions</td>
</tr>
<tr>
<td class="label">WGR domain</td>
<td>Nucleic acid binding (tryptophan-glycine-arginine)</td>
</tr>
<tr>
<td class="label">BRCT domain</td>
<td>DNA damage response (breast cancer C-terminal)</td>
</tr>
<tr>
<td class="label">Catalytic domain</td>
<td>PAR synthesis activity</td>
</tr>
<tr>
<td class="label">Pathway</td>
<td>Role</td>
</tr>
<tr>
<td class="label">Base excision repair (BER)</td>
<td>Assists in repair of small lesions</td>
</tr>
<tr>
<td class="label">Single-strand break repair</td>
<td>Contributes to SSB detection</td>
</tr>
<tr>
<td class="label">Double-strand break response</td>

PARP4 — Poly(ADP-Ribose) Polymerase 4

Overview

<table class="infobox infobox-gene">
<tr>
<th class="infobox-header" colspan="2">PARP4 — Poly(ADP-Ribose) Polymerase 4</th>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>PARP4</td>
</tr>
<tr>
<td class="label">Protein</td>
<td>Poly(ADP-ribose) polymerase 4 (Vault PARP, vPARP)</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>13q12.12</td>
</tr>
<tr>
<td class="label">NCBI Gene ID</td>
<td>8548</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q9UKK3</td>
</tr>
<tr>
<td class="label">Aliases</td>
<td>PARP4, ARTD4, vPARP</td>
</tr>
<tr>
<td class="label">Domain</td>
<td>Function</td>
</tr>
<tr>
<td class="label">N-terminal region</td>
<td>Protein-protein interactions</td>
</tr>
<tr>
<td class="label">WGR domain</td>
<td>Nucleic acid binding (tryptophan-glycine-arginine)</td>
</tr>
<tr>
<td class="label">BRCT domain</td>
<td>DNA damage response (breast cancer C-terminal)</td>
</tr>
<tr>
<td class="label">Catalytic domain</td>
<td>PAR synthesis activity</td>
</tr>
<tr>
<td class="label">Pathway</td>
<td>Role</td>
</tr>
<tr>
<td class="label">Base excision repair (BER)</td>
<td>Assists in repair of small lesions</td>
</tr>
<tr>
<td class="label">Single-strand break repair</td>
<td>Contributes to SSB detection</td>
</tr>
<tr>
<td class="label">Double-strand break response</td>
<td>May participate in HR/NHEJ</td>
</tr>
<tr>
<td class="label">Cell Type</td>
<td>Expression</td>
</tr>
<tr>
<td class="label">Neurons</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Astrocytes</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Microglia</td>
<td>Low</td>
</tr>
<tr>
<td class="label">Oligodendrocytes</td>
<td>Low</td>
</tr>
<tr>
<td class="label">Protein</td>
<td>Interaction Type</td>
</tr>
<tr>
<td class="label">Major Vault Protein (MVP)</td>
<td>Physical complex</td>
</tr>
<tr>
<td class="label">PARP1</td>
<td>Functional</td>
</tr>
<tr>
<td class="label">XRCC1</td>
<td>Interaction</td>
</tr>
<tr>
<td class="label">DNA ligase III</td>
<td>Interaction</td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">1 edges</a></td>
</tr>
</table>

PARP4 (Poly(ADP-Ribose) Polymerase 4), also known as vault PARP (vPARP) or ARTD4, encodes a member of the poly(ADP-ribose) polymerase family. While PARP1 and PARP2 are well-characterized for their roles in DNA damage response, PARP4 has distinct functions, particularly in association with vault particles—large ribonucleoprotein complexes involved in cellular transport and signaling. PARP4 is implicated in DNA repair, cellular stress responses, and has emerging roles in neurodegeneration[@ame2019].

Structure and Function

Protein Domains

PARP4 contains several distinct structural domains:

Vault Particle Association

PARP4 is unique among PARP family members in its association with vault particles:

• Vaults are large (~13 MDa) ribonucleoprotein complexes
• Major vault protein (MVP) forms the structural core
• PARP4 localizes to the interior of vault particles
• May regulate vault function or cargo transport[@yelick2017]

Catalytic Activity

Like other PARPs, PARP4 can catalyze poly(ADP-ribosyl)ation (PARylation):

• Uses NAD+ as substrate
• Synthesizes poly(ADP-ribose) chains
• Modifies target proteins
• Auto-modification (automodification) is also observed

Normal Physiological Functions

DNA Damage Response

PARP4 participates in DNA repair pathways:

Vault Particle Functions

Vault particles are implicated in:

• Drug resistance: Overexpression associated with chemoresistance
• Intracellular transport: Cargo between nucleus and cytoplasm
• Signal transduction: May act as scaffolds for signaling complexes

Cellular Stress Responses

PARP4 responds to various cellular stresses:

• Oxidative stress
• Genotoxic stress
• Metabolic stress

Role in Neurodegenerative Diseases

Alzheimer's Disease

PARP4 is increasingly recognized in AD pathogenesis[@song2020]:

Mechanisms:

• DNA damage accumulation: Neurons in AD show extensive DNA damage
• PARP activation: Compensatory response to genotoxic stress
• NAD+ depletion: Overactivation depletes cellular NAD+
• Energy failure: PARP overactivation contributes to bioenergetic collapse

• PARP expression is elevated in AD brain
• PARP1/PARP4 may have overlapping functions
• Combined effects on neuronal survival

Parkinson's Disease

PARP involvement in PD relates to mitochondrial dysfunction[@jiang2016]:

Mechanisms:

• Mitochondrial DNA damage: Oxidative stress causes mtDNA lesions
• PARP activation: Response to mitochondrial dysfunction
• NAD+ metabolism: Altered NAD+ levels affect neuronal survival
• Alpha-synuclein interaction: Possible cross-talk with PARP pathways

• PARP activation in PD models and patient tissue
• PARP inhibitors show protective effects
• NAD+ boosting strategies under investigation

Stroke and Ischemia

PARP4 contributes to post-ischemic injury:

• Ischemia causes massive DNA damage
• PARP activation leads to NAD+ depletion
• Energy failure contributes to cell death
• PARP4 may contribute to this pathway

ALS (Amyotrophic Lateral Sclerosis)

• DNA damage accumulates in motor neurons
• PARP activation contributes to degeneration
• Therapeutic targeting under investigation

Clinical Significance

Cancer

PARP4 has been studied in cancer contexts:

• Overexpression in some tumors
• Association with drug resistance
• Vault-mediated drug sequestration

Neurodegeneration

While not a primary disease-causing gene, PARP4 may modify neurodegeneration:

• Genetic variants may affect disease risk or progression
• Protein expression changes in disease states
• May interact with other PARP family members

Therapeutic Implications

PARP Inhibitors

Current PARP inhibitors primarily target PARP1/PARP2:

• Olaparib: FDA-approved for breast/ovarian cancer
• Rucaparib, Niraparib, Talazoparib: Approved in oncology
• In development: Neuroprotective PARP inhibitors

Specific Considerations for PARP4

• PARP4 may have distinct substrate preferences
• Vault-associated functions may be targetable
• Combined PARP1/4 targeting may be beneficial

NAD+ Boosting Strategies

Given PARP-mediated NAD+ depletion:

• Nicotinamide riboside (NR): NAD+ precursor
• Nicotinamide mononucleotide (NMN): NAD+ precursor
• Apigenin: SIRT1 activator (NAD+-dependent)

Expression Pattern

Brain Regions

PARP4 is expressed in:

• Cerebral cortex
• [Hippocampus](/brain-regions/hippocampus)
• [Cerebellum](/brain-regions/cerebellum)
• Substantia nigra
• Spinal cord

Cell Type Specificity

Key Interactions

Animal Models

Knockout Mice

• Parp4-/-: Viable, with subtle phenotypes
• Increased tumor susceptibility: DNA repair defects
• Vault structure unchanged: Redundant functions

Disease Models

• AD models: Crossed with APP/tau mice
• PD models: MPTP, 6-OHDA models
• Stroke models: Transient MCAO

Research Methods

Biochemistry

• PARylation assays
• NAD+ measurement
• DNA damage markers

Molecular Biology

• siRNA/shRNA knockdown
• CRISPR-Cas9 editing
• Co-immunoprecipitation

Imaging

• Immunofluorescence for vault particles
• Subcellular localization
• PAR polymer detection

See Also

• [Poly(ADP-Ribose) Polymerase Family](/mechanisms/parp-family)
• [DNA Damage Response](/mechanisms/dna-damage-response)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Parkinson's Disease](/diseases/parkinsons-disease)
• [Vault Particles](/mechanisms/vault-particles)

References