| Property | Value |
|---|---|
| Gene Symbol | UBE2V1 |
| Full Name | Ubiquitin-Conjugating Enzyme E2 Variant 1 |
| Alternative Names | UEV-1, UEV1, CROC-1, CIR1 |
| Chromosomal Location | 20q13.33 |
| NCBI Gene ID | 7335 |
| OMIM | 603416 |
| Ensembl ID | ENSG00000109343 |
| UniProt ID | Q13435 |
| Gene Family | Ubiquitin-conjugating enzyme (E2) family, UEV subfamily |
| Associated Diseases | Neurodegeneration, Cancer, Inflammatory Disorders |
| UBE2V1 (UEV-1) | |
|---|---|
| Gene Symbol | UBE2V1 (UEV-1) |
| Full Name | Ubiquitin-Conjugating Enzyme E2 Variant 1 |
| Chromosome | 20q13.33 |
| NCBI Gene ID | [7335](https://www.ncbi.nlm.nih.gov/gene/7335) |
| OMIM | 603416 |
| Ensembl ID | [ENSG00000109343](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000109343) |
| UniProt ID | [Q13435](https://www.uniprot.org/uniprot/Q13435) |
| Associated Diseases | Neurodegeneration, Cancer, Inflammatory Disorders |
UBE2V1 (Ubiquitin-Conjugating Enzyme E2 Variant 1), also known as UEV-1 (Ubiquitin E2 Variant 1), CROC-1, or CIR1, is a unique member of the ubiquitin-conjugating enzyme (E2) family. Unlike canonical E2 enzymes that catalyze ubiquitin transfer through formation of a thioester bond with the active site cysteine, UBE2V1 lacks this critical cysteine residue and functions as an E2 variant that regulates ubiquitin chain assembly without directly catalyzing ubiquitin transfer.
UBE2V1 plays essential roles in several critical cellular pathways, most notably in K63-linked polyubiquitination—a non-degradative ubiquitin modification that regulates signal transduction, DNA damage repair, protein trafficking, and inflammatory responses. Through its interaction with UBE2N (Ubc13), UBE2V1 forms a heterodimeric complex that generates free K63-linked polyubiquitin chains, which serve as signaling platforms for NF-κB activation, DNA damage response, and other cellular processes.
In the context of neurodegenerative diseases, UBE2V1 has emerged as an important regulator of neuroinflammation, DNA repair, and protein quality control—processes that are central to neuronal survival and function. Dysregulation of UBE2V1 and K63-linked ubiquitination has been implicated in Alzheimer's disease, Parkinson's disease, and other neurodegenerative disorders.
The UBE2V1 gene is located on chromosome 20q13.33 and encodes a protein of approximately 17 kDa. The gene is conserved across eukaryotes, with orthologs in yeast (Mms2), flies, and other species.
UBE2V1 belongs to the UEV (Ubiquitin-Conjugating Enzyme Variant) subfamily of E2-like proteins. Key structural features include:
Ubiquitin-Conjugating Fold: UBE2V1 adopts the characteristic UBC fold, a three-helix bundle with a central β-sheet. However, the protein diverges from canonical E2s in several important ways.
Active Site Alteration: UBE2V1 lacks the catalytic cysteine residue present in active E2 enzymes. Instead, it has a serine at position 89 (in human UBE2V1), which cannot form a thioester bond with ubiquitin. This renders it catalytically inactive for direct ubiquitin transfer but allows it to function as a regulator.
UEV Domain: The N-terminus contains a UEV-specific region that mediates protein-protein interactions, particularly with ubiquitin and other proteins.
Dimerization Interface: UBE2V1 can form homodimers and heterodimers with UBE2N (Ubc13), which is essential for its function in K63-linked ubiquitination.
UBE2V1 has multiple isoforms resulting from alternative splicing, including:
UBE2V1's primary function is to act as a regulatory partner to UBE2N (Ubc13), forming a heterodimeric complex that catalyzes K63-linked polyubiquitination. This complex is unique among E2 enzymes in that:
Complex Formation: UBE2V1 binds to UBE2N through a high-affinity interaction, forming a stable heterodimer. This interaction positions UBE2V1 to regulate the ubiquitination process.
E2-E2 Communication: The complex represents a novel mechanism where one E2 variant (UBE2V1) regulates the activity of a canonical E2 (UBE2N). UBE2V1 provides the UEV domain that allows interaction with ubiquitin and the growing chain, while UBE2N provides the catalytic activity.
Chain Elongation: The UBE2N-UBE2V1 complex specifically synthesizes K63-linked polyubiquitin chains. This linkage specificity is determined by both the E2 and the UEV component.
K63-linked polyubiquitination involves the assembly of ubiquitin chains through isopeptide bonds linking the C-terminal glycine of one ubiquitin to the lysine 63 (K63) of the previous ubiquitin. Unlike K48-linked chains (which signal for proteasomal degradation), K63-linked chains serve non-degradative functions:
Signaling Scaffolds: K63-linked chains serve as platforms for protein complex assembly, recruiting signaling proteins to activated receptors and damaged DNA.
Protein Activation: K63-linked ubiquitination can activate enzymes by promoting conformational changes or by facilitating dimerization.
Protein Trafficking: K63-linked chains regulate endocytosis, sorting, and trafficking of membrane proteins.
UBE2V1-mediated K63-linked polyubiquitination is a critical regulator of NF-κB signaling:
Receptor Signaling: Upon activation of various receptors (TNF receptor, TLRs, IL-1R), K63-linked ubiquitination of adaptor proteins (RIPK1, TRAF6, TAK1) creates signaling platforms that recruit and activate the IKK complex.
IKK Activation: The IKK complex (IKKα, IKKβ, IKKγ/NEMO) is recruited to ubiquitinated signaling complexes, leading to its activation through phosphorylation.
IκB Degradation: Activated IKK phosphorylates IκBα, targeting it for K48-linked ubiquitination and proteasomal degradation. This releases NF-κB (p65/p50) to translocate to the nucleus.
Gene Expression: NF-κB induces expression of inflammatory cytokines (TNF, IL-1β, IL-6), anti-apoptotic proteins (Bcl-2, c-IAP), and other genes involved in immune and inflammatory responses.
Negative Regulation: UBE2V1 also contributes to negative regulation of NF-κB through assembly of regulatory complexes that control signal termination.
K63-linked ubiquitination is essential for the DNA damage response:
PCNA Monoubiquitination: UBE2V1 can regulate PCNA (Proliferating Cell Nuclear Antigen) monoubiquitination, which is critical for translesion DNA synthesis and error-free repair.
Checkpoint Activation: K63-linked ubiquitination of proteins involved in DNA damage checkpoint activation (e.g., 53BP1, BRCA1) facilitates recruitment of repair factors to damaged DNA.
Repair Factor Recruitment: Ubiquitin chains generated by UBE2V1-containing complexes serve as landing pads for proteins containing ubiquitin-binding domains (UBDs), such as RAP80, BRCA1, and 53BP1.
UBE2V1 also regulates MAPK (Mitogen-Activated Protein Kinase) signaling[1]:
JNK Activation: K63-linked ubiquitination modulates JNK pathway activation in response to stress and cytokines. The JNK pathway is particularly relevant to neuronal stress and apoptosis.
p38 Activation: Similar regulation of p38 MAPK signaling. The p38 pathway is involved in inflammatory responses and cell survival decisions.
ERK Pathway: UBE2V1 may affect ERK signaling in certain contexts, linking ubiquitination to cell proliferation and differentiation.
UBE2V1 plays roles in autophagy and protein quality control[2]:
Selective autophagy: K63-linked chains can serve as autophagy receptors, targeting ubiquitinated proteins and organelles for autophagic degradation.
Aggresome clearance: UBE2V1-mediated ubiquitination helps target misfolded proteins to aggresomes for disposal.
Mitophagy: K63-linked ubiquitination of mitochondrial proteins marks damaged mitochondria for selective autophagic removal.
UBE2V1 is ubiquitously expressed with high levels in:
UBE2V1 localizes primarily to:
UBE2V1 expression is regulated at multiple levels:
UBE2V1 and K63-linked ubiquitination are implicated in AD pathogenesis:
Neuroinflammation: NF-κB activation by UBE2V1-mediated ubiquitination drives chronic neuroinflammation in AD. Elevated UBE2V1 expression in AD brains correlates with increased inflammatory markers.
Amyloid-beta metabolism: K63-linked ubiquitination affects amyloid precursor protein (APP) processing and amyloid-beta (Aβ) secretion. Some studies suggest UBE2V1 may modulate these pathways.
Tau pathology: K63-linked ubiquitination of tau may affect its aggregation and clearance. The balance between K63 and other ubiquitin linkages influences tau pathology.
Synaptic dysfunction: UBE2V1-mediated signaling affects synaptic function and plasticity. Dysregulation contributes to synaptic loss in AD.
Therapeutic potential: Modulating UBE2V1 activity or K63-linked ubiquitination could potentially reduce neuroinflammation and improve protein clearance in AD.
UBE2V1 contributes to PD pathogenesis through multiple mechanisms:
α-Synuclein metabolism: K63-linked ubiquitination plays roles in α-synuclein aggregation and clearance. UBE2V1 may affect the balance between toxic aggregation and autophagic clearance.
Mitochondrial function: UBE2V1-mediated ubiquitination affects mitochondrial quality control. Dysregulation contributes to mitochondrial dysfunction, a central feature of PD.
Neuroinflammation: NF-κB activation driven by UBE2V1 promotes microglial activation and dopaminergic neuron death.
LRRK2 interaction: LRRK2 (a major PD gene) interacts with the ubiquitination machinery, and UBE2V1 may modulate LRRK2-related pathways.
UBE2V1 involvement in ALS includes:
Protein homeostasis: Impaired proteostasis is a hallmark of ALS. UBE2V1-mediated K63-linked ubiquitination affects protein quality control pathways.
RNA metabolism: Some ALS-linked proteins are regulated by ubiquitination, and UBE2V1 may affect these pathways.
Neuroinflammation: NF-κB activation in ALS involves UBE2V1-dependent ubiquitination, contributing to glial activation and motor neuron injury.
UBE2V1 may also play roles in:
UBE2V1 has a closely related paralog, UBE2V2 (UBE2V2/MMS2), which shares similar functions:
| Feature | UBE2V1 | UBE2V2 |
|---|---|---|
| Alternative names | UEV-1, CROC-1 | UEV-2, MMS2 |
| Chromosome | 20q13.33 | 8q24.3 |
| Function | K63-linked ubiquitination | K63-linked ubiquitination |
| Expression | Ubiquitous, high in brain | Ubiquitous |
| Interactions | UBE2N | UBE2N |
Both UBE2V1 and UBE2V2 can form heterodimers with UBE2N and participate in K63-linked ubiquitination, though they may have some tissue-specific or pathway-specific functions.
Modulating UBE2V1 activity represents a potential therapeutic strategy:
NF-κB inhibitors: Since UBE2V1 is required for NF-κB activation, inhibitors of the UBE2N-UBE2V1 complex could reduce harmful neuroinflammation while potentially preserving some protective immunity.
Protein clearance enhancers: K63-linked ubiquitination affects autophagic and proteasomal clearance. Modulating this pathway could improve clearance of toxic proteins in neurodegeneration.
Anti-inflammatory approaches: Small molecules targeting the UBE2N-UBE2V1 complex could reduce cytokine production in neuroinflammatory conditions.