Ubiquitin-conjugating enzyme E2 variant 2 is a protein that in humans is encoded by the UBE2V2 gene. [5] [6] Ubiquitin-conjugating enzyme E2 variant proteins constitute a distinct subfamily within the E2 protein family.
UBE2V2 has sequence similarity to other ubiquitin-conjugating enzymes but lack the conserved cysteine residue that is critical for the catalytic activity of E2s. The protein encoded by this gene also shares homology with ubiquitin-conjugating enzyme E2 variant 1 and yeast MMS2 gene product. [7]
UBE2V2 has also been implicated as an intracellular sensor of reactive electrophilic species, which are present in high levels during periods of pathogenic and/or environmental stress. [8] The C69 residue of UBE2V2 is capable of binding with various RES. It has been shown that binding of RES to UBE2V2 promotes UBE2V2-mediated activation of Ube2N, another E2 protein that complexes with UBE2V2. Activated Ube2N has been shown to play a major role in promoting DNA-damage responses. Thus, UBE2V2 may promote genome integrity by directly sensing RES and effecting DNA damage responses. [9] It may also be involved in the differentiation of monocytes and enterocytes. [7]
UBE2V2 has been shown to interact with HLTF. [10] Although UBE2V2 itself lacks ubiquitin-conjugating activity, it can interact with different Ubiquitin-conjugating enzymes to facilitate their catalytic activities. [11] For instance, UBE2V2 can complex with UBE2N to form a heterodimer capable of synthesizing Lys-63 linked polyubiquitin chains. [12] UBE2V2 may facilitate UBE2N activity by coordinating UBE2N's positioning to promote ubiquitin chain formation specifically at Lys-63, as the ubiquitin molecule has multiple potential Lysine binding sites. [13] Similarly, it has been shown that UBE2V2 interact with the ubiquitin-conjugating enzyme, Ubc13, to induce Ubc13 to adopt an active conformation that can create Lys-63 polyubiquitin chains on various substrates. [14]
Addition of Lys-63 polyubiquitin chains to intracellular targets is distinct from the canonical Lys-48 polyubiquitin chains in that Lys-63 chains do not mediate proteasomal degradation of its substrate. [15] Although their function remains poorly characterized, Lys-63 chains have been shown to regulate signaling pathways by either activating or inhibiting its target protein function. [16] For example, TRIM5alpha restriction of retroviral reverse-transcription is dependent on UBE2V2/UBE2N-mediated poly-ubiquitination. [17] UBE2V2 has been shown to regulate TRIM21 antiviral activity in an analogous manner. [18]
Ubiquitin is a small regulatory protein found in most tissues of eukaryotic organisms, i.e., it is found ubiquitously. It was discovered in 1975 by Gideon Goldstein and further characterized throughout the late 1970s and 1980s. Four genes in the human genome code for ubiquitin: UBB, UBC, UBA52 and RPS27A.
A ubiquitin ligase is a protein that recruits an E2 ubiquitin-conjugating enzyme that has been loaded with ubiquitin, recognizes a protein substrate, and assists or directly catalyzes the transfer of ubiquitin from the E2 to the protein substrate. The ubiquitin is attached to a lysine on the target protein by an isopeptide bond. E3 ligases interact with both the target protein and the E2 enzyme, and so impart substrate specificity to the E2. Commonly, E3s polyubiquitinate their substrate with Lys48-linked chains of ubiquitin, targeting the substrate for destruction by the proteasome. However, many other types of linkages are possible and alter a protein's activity, interactions, or localization. Ubiquitination by E3 ligases regulates diverse areas such as cell trafficking, DNA repair, and signaling and is of profound importance in cell biology. E3 ligases are also key players in cell cycle control, mediating the degradation of cyclins, as well as cyclin dependent kinase inhibitor proteins. The human genome encodes over 600 putative E3 ligases, allowing for tremendous diversity in substrates.
Deubiquitinating enzymes (DUBs), also known as deubiquitinating peptidases, deubiquitinating isopeptidases, deubiquitinases, ubiquitin proteases, ubiquitin hydrolases, ubiquitin isopeptidases, are a large group of proteases that cleave ubiquitin from proteins. Ubiquitin is attached to proteins in order to regulate the degradation of proteins via the proteasome and lysosome; coordinate the cellular localisation of proteins; activate and inactivate proteins; and modulate protein-protein interactions. DUBs can reverse these effects by cleaving the peptide or isopeptide bond between ubiquitin and its substrate protein. In humans there are nearly 100 DUB genes, which can be classified into two main classes: cysteine proteases and metalloproteases. The cysteine proteases comprise ubiquitin-specific proteases (USPs), ubiquitin C-terminal hydrolases (UCHs), Machado-Josephin domain proteases (MJDs) and ovarian tumour proteases (OTU). The metalloprotease group contains only the Jab1/Mov34/Mpr1 Pad1 N-terminal+ (MPN+) (JAMM) domain proteases.
SUMO-conjugating enzyme UBC9 is an enzyme that in humans is encoded by the UBE2I gene. It is also sometimes referred to as "ubiquitin conjugating enzyme E2I" or "ubiquitin carrier protein 9", even though these names do not accurately describe its function.
Polyubiquitin-C is a protein encoded by the UBC gene in humans. Polyubiquitin-C is one of the sources of ubiquitin, along with UBB, UBA52, and RPS27A.
Ubiquitin-conjugating enzyme E2 L3 (UBE2L3), also called UBCH7, is a protein that in humans is encoded by the UBE2L3 gene. As an E2 enzyme, UBE2L3 participates in ubiquitination to target proteins for degradation. The role of UBE2L3 in the ubiquitination of the NF-κB precursor implicated it in various major autoimmune diseases, including rheumatoid arthritis (RA), celiac disease, Crohn's disease (CD), and systemic lupus erythematosus.
CDC34 is a gene that in humans encodes the protein Ubiquitin-conjugating enzyme E2 R1. This protein is a member of the ubiquitin-conjugating enzyme family, which catalyzes the covalent attachment of ubiquitin to other proteins.
Ubiquitin-conjugating enzyme E2 N is a protein that in humans is encoded by the UBE2N gene.
Ubiquitin-conjugating enzyme E2 D1 is a protein that in humans is encoded by the UBE2D1 gene.
Ubiquitin-conjugating enzyme E2 D2 is a protein that in humans is encoded by the UBE2D2 gene.
Ubiquitin-conjugating enzyme E2 G2 is a protein that in humans is encoded by the UBE2G2 gene.
NEDD8-activating enzyme E1 catalytic subunit is a protein that in humans is encoded by the UBA3 gene.
Ubiquitin-conjugating enzyme E2 E3 is a protein that in humans is encoded by the UBE2E3 gene.
Ubiquitin/ISG15-conjugating enzyme E2 L6 is a protein that in humans is encoded by the UBE2L6 gene.
Ubiquitin-conjugating enzyme E2 variant 1 is a protein that in humans is encoded by the UBE2V1 gene.
Ubiquitin-conjugating enzyme E2 C is a protein that in humans is encoded by the UBE2C gene.
Ubiquitin-conjugating enzyme E2 G1 is a protein that in humans is encoded by the UBE2G1 gene.
Ubiquitin-conjugating enzyme E2 variant 1, also known as Kua-UEV, is a human gene.
Ubiquitin-conjugating enzyme E2 J1 is a protein that in humans is encoded by the UBE2J1 gene.
NEDD8-conjugating enzyme Ubc12 is a protein that in humans is encoded by the UBE2M gene.