| Pathway/Process | Specific Role of UBE2L6 | Key Target Proteins/Substrates | Biological Outcome |
|---|---|---|---|
| ISGylation pathway and interferon response | UBE2L6 is the principal E2 enzyme in the ISG15 conjugation cascade induced by type I interferon; it receives activated ISG15 from UBA7/UBE1L and transfers it to substrates with E3 ligases such as HERC5, TRIM25, and HHARI. In cells, UBE2L6 shows higher functional affinity for the ISG15 pathway than for canonical ubiquitin transfer. (pqac-00000001, pqac-00000007, pqac-00000008, pqac-00000014) | ISG15; UBA7/UBE1L; HERC5, TRIM25, HHARI; broad host and viral protein substrates | Establishes interferon-stimulated ISGylation, a core antiviral and stress-response pathway that remodels protein stability, interactions, and signaling. (pqac-00000001, pqac-00000008, pqac-00000014) |
| Innate antiviral immunity | UBE2L6 supports antiviral defense by enabling ISGylation of host and viral proteins and by participating in interferon-stimulated effector programs. Its expression is induced with ISG15 pathway genes downstream of IFN/JAK-STAT signaling. (pqac-00000004, pqac-00000008, pqac-00000013) | Viral proteins such as influenza NP and other newly synthesized viral proteins via HERC5-associated cotranslational ISGylation; host antiviral signaling proteins | Restricts viral protein synthesis, assembly, and replication, and amplifies innate immune responsiveness. In some virus-host contexts, pathogens can hijack UBE2L6 to weaken immunity. (pqac-00000008, pqac-00000013, pqac-00000010) |
| Regulation of RIG-I/MDA5 signaling | UBE2L6 modulates RIG-I-like receptor signaling through ubiquitin/ISG15-dependent mechanisms. During PRRSV infection, elevated UBE2L6 promotes K48-linked ubiquitination and proteasomal loss of RIG-I and MDA5, aided by viral NSP5; broader ISG15 literature also links ISGylation to RIG-I/MDA5 regulation. (pqac-00000010, pqac-00000013) | RIG-I, MDA5, PRRSV NSP5, K48-linked ubiquitin, ISG15 | Suppresses type I IFN and ISG expression during PRRSV infection, facilitating viral replication; demonstrates that UBE2L6 can either support host defense or be co-opted by viruses. (pqac-00000010) |
| STAT1 signaling and macrophage polarization | In obese mouse models, Ube2L6 promotes STAT1 ISGylation/ISG15-dependent activation, increasing STAT1 abundance and phosphorylation and biasing macrophages toward a pro-inflammatory M1 state. (pqac-00000005, pqac-00000011) | STAT1, ISG15, macrophage polarization machinery | Enhances M1 macrophage polarization, inflammatory cytokine production, and obesity-associated inflammation; Ube2L6 deficiency shifts macrophages away from the M1 phenotype. (pqac-00000005, pqac-00000011) |
| Adipocyte metabolism and lipid regulation | In adipose tissue, Ube2L6 negatively regulates ATGL stability and thereby restrains lipolysis. Adipose-specific Ube2l6 knockout in mice increases ATGL stability and alters adipocyte size and differentiation under high-fat diet conditions. Human obesity datasets/tissues also show inverse UBE2L6-ATGL association and positive correlation with BMI. (pqac-00000012) | ATGL/PNPLA2; adipocyte lipid-droplet/lipolysis machinery | Promotes diet-induced obesity, insulin resistance, hepatic steatosis, and adipose expansion when elevated; loss of Ube2L6 improves metabolic phenotype in mice. (pqac-00000012) |
| Protein quality control and proteostasis | Through the ISG15 system, UBE2L6 contributes to proteostasis by promoting cotranslational ISGylation of newly synthesized proteins together with HERC5, altering ubiquitin-dependent turnover and helping manage misfolded, viral, or stress-induced substrates. Reduced UBE2L6 lowers ISGylation and can increase ubiquitination in some cancer-cell models. (pqac-00000006, pqac-00000013) | Newly synthesized proteins, ubiquitin, ISG15, HERC5-associated polysome substrates, Ubc13 and other proteostasis-linked factors | Regulates stability and turnover of protein substrates, restricts nascent viral proteins, and contributes to the balance between ISGylation and ubiquitin-proteasome pathways. (pqac-00000006, pqac-00000013) |
| DNA damage response | UBE2L6 participates in the ISG15 system increasingly linked to genome stability. Reviews identify UBE2L6-dependent ISGylation as part of pathways affecting p53 signaling, replication stress responses, and DNA repair-associated proteome remodeling. (pqac-00000007, pqac-00000013) | ISG15 pathway components; DDR-associated proteins including p53-network and replication/repair factors discussed in ISG15 studies | Suggests a role in maintaining genome stability and modulating DNA damage responses, though many UBE2L6-specific substrates in this context remain incompletely defined. (pqac-00000007, pqac-00000013) |
| Autophagy regulation | UBE2L6 contributes indirectly to autophagy-related control through ISGylation-dependent regulation of proteins such as BECN1 and by modulating antiviral signaling nodes that connect to autophagic degradation pathways. ISG15 literature also links ISGylation to RIG-I-associated autophagy control. (pqac-00000006, pqac-00000013) | BECN1, RIG-I-associated complexes, ISG15-modified stress-response proteins | Can influence antiviral autophagy and selective degradation pathways, thereby integrating innate immune signaling with cellular quality-control responses. (pqac-00000006, pqac-00000013) |


*Table: This table summarizes experimentally supported and review-backed roles of UBE2L6 across interferon signaling, antiviral immunity, metabolism, inflammation, and proteostasis. It is useful for functional annotation because it links pathway membership to specific substrates and biological outcomes.*