{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nUBE2L6, also known as UbcH8, is a versatile E2 enzyme that participates in both ubiquitination and ISGylation pathways. Structural studies have demonstrated that UBE2L6 covalently binds ubiquitin via a conserved active‐site cysteine and engages unique regions—such as the linker segment preceding the α5 helix and adjoining surfaces—to secure ubiquitin in a distinct orientation. These features not only enable the enzyme to accept ubiquitin from the E1 enzyme but also allow it to interact efficiently with select E3 ligases, thereby contributing an additional layer of substrate specificity in the ubiquitination cascade."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "1"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nIn cancer contexts, UBE2L6 plays multifaceted roles in modulating cell fate. In acute myeloid leukemia, for example, treatment with histone deacetylase inhibitors induces UBE2L6 expression, which in turn, in concert with the ubiquitin ligase SIAH1, promotes the proteasomal degradation of the oncogenic FLT3-ITD, thereby impairing leukemic cell survival. Beyond this, UBE2L6 acts with the CRL4(Cdt2) E3 ligase to ubiquitylate key cell cycle regulators such as p21 and Set8, emphasizing its importance in cell cycle control. Epigenetic silencing of UBE2L6 through promoter hypermethylation has been observed in nasopharyngeal and cervical cancers—with its down-regulation correlating with diminished apoptotic responses—whereas its restoration promotes apoptosis and supports all-trans-retinoic acid-induced neutrophil differentiation in acute promyelocytic leukemia. Similarly, transient knockdown of BRCA2 has been associated with reduced UBE2L6 expression, pointing to a broader role for UBE2L6 in maintaining proper cell cycle dynamics."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "3", "end_ref": "8"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nBeyond its intracellular regulatory roles, UBE2L6 is emerging as a potential biomarker and mediator of therapeutic responses in diverse diseases. In esophageal cancer, higher expression levels of UBE2L6 and ISG15 components are associated with a reduction in autophagic flux and improved chemosensitivity, whereas in ovarian cancer, UBE2L6 upregulation has been linked to cisplatin resistance through modulation of ABCB6 expression. Pro-inflammatory factors such as TNF-α also stimulate the expression of UBE2L6 and its conjugation machinery in lung carcinoma via MAPK pathways. Finally, transcriptomic analyses have identified UBE2L6 as a core gene upregulated in COVID-19, and its functional involvement in suppressing apoptosis in Mycobacterium tuberculosis-infected macrophages underscores its potential utility as a biomarker in tuberculosis."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "9", "end_ref": "14"}]}, {"type": "t", "text": "\n"}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Larissa A Durfee, Melissa L Kelley, Jon M Huibregtse "}, {"type": "b", "children": [{"type": "t", "text": "The basis for selective E1-E2 interactions in the ISG15 conjugation system."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "J Biol Chem (2008)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1074/jbc.M804069200"}], "href": "https://doi.org/10.1074/jbc.M804069200"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "18583345"}], "href": "https://pubmed.ncbi.nlm.nih.gov/18583345"}]}, {"type": "r", "ref": 2, "children": [{"type": "t", "text": "Stephanie A Serniwka, Gary S Shaw "}, {"type": "b", "children": [{"type": "t", "text": "The structure of the UbcH8-ubiquitin complex shows a unique ubiquitin interaction site."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Biochemistry (2009)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1021/bi901686j"}], "href": "https://doi.org/10.1021/bi901686j"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "19928833"}], "href": "https://pubmed.ncbi.nlm.nih.gov/19928833"}]}, {"type": "r", "ref": 3, "children": [{"type": "t", "text": "Manish K Tripathi, Gautam Chaudhuri "}, {"type": "b", "children": [{"type": "t", "text": "Down-regulation of UCRP and UBE2L6 in BRCA2 knocked-down human breast cells."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Biochem Biophys Res Commun (2005)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1016/j.bbrc.2004.12.142"}], "href": "https://doi.org/10.1016/j.bbrc.2004.12.142"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "15670748"}], "href": "https://pubmed.ncbi.nlm.nih.gov/15670748"}]}, {"type": "r", "ref": 4, "children": [{"type": "t", "text": "M Buchwald, K Pietschmann, J P Müller, et al. 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