{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nUFD1 functions as a pivotal adaptor within the p97/VCP–UFD1–Npl4 complex that extracts ubiquitinated substrates and channels them for proteasomal degradation. In this capacity, UFD1 not only facilitates the recognition and unfolding of polyubiquitylated proteins in endoplasmic reticulum–associated degradation (ERAD) but also modulates the activity of associated E3 ubiquitin ligases (such as gp78) and cooperating factors (including FAF1 and NUB1L) that fine‐tune substrate ubiquitination. Moreover, post‐translational modifications such as phosphorylation (e.g., by protein kinase A) directly modulate UFD1’s binding affinity for p97, thereby regulating the efficiency of target protein processing."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "13"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nBeyond its central role in protein quality control, UFD1 also regulates critical cellular pathways that govern cell cycle progression, stress responses, and signal transduction. By controlling the removal of key regulatory proteins – for instance, facilitating the timely degradation of mitotic factors such as Aurora B and CDC25A, as well as processing NF‑κB precursors (p100 to p52) – the p97–UFD1–Npl4 complex helps maintain genomic stability and proper cell cycle checkpoints. Moreover, dysregulation of UFD1 activity has been implicated in diverse human pathologies; altered UFD1 expression or genetic variants have been linked to neurocognitive abnormalities in disorders such as schizophrenia and 22q11.2 deletion syndrome, while in specific cancers (including T‑cell acute lymphoblastic leukemia and breast cancer) aberrant UFD1 levels contribute to oncogenic signaling and enhanced cellular survival."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "14", "end_ref": "21"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nRecent structural and mechanistic studies have further refined our understanding of UFD1’s function within the p97 machinery. High‐resolution crystallographic analyses and site‐directed mutagenesis have delineated the molecular architecture of the UFD1–Npl4 heterodimer, revealing key binding domains that govern its interactions with p97 and ubiquitin chains. Such studies have also demonstrated that oncogenic mutations in p97 can lead to tighter association with UFD1, suggestive of a gain‐of‐function that may underlie certain proteinopathies. Together, these insights emphasize that UFD1 operates as a critical nodal point integrating ubiquitin signals with stress response, cell cycle regulation, and viral as well as oncogenic processes."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "10"}, {"type": "fg_f", "ref": "22"}, {"type": "fg_f", "ref": "11"}, {"type": "fg_f", "ref": "23"}, {"type": "fg_f", "ref": "12"}]}, {"type": "t", "text": "\n"}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Francesca Amati, Emanuela Conti, Annalisa Botta, et al. 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"}, {"type": "b", "children": [{"type": "t", "text": "Ufd1 is a cofactor of gp78 and plays a key role in cholesterol metabolism by regulating the stability of HMG-CoA reductase."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Cell Metab (2007)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1016/j.cmet.2007.07.002"}], "href": "https://doi.org/10.1016/j.cmet.2007.07.002"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "17681147"}], "href": "https://pubmed.ncbi.nlm.nih.gov/17681147"}]}, {"type": "r", "ref": 5, "children": [{"type": "t", "text": "Nia Soetandyo, Yihong Ye "}, {"type": "b", "children": [{"type": "t", "text": "The p97 ATPase dislocates MHC class I heavy chain in US2-expressing cells via a Ufd1-Npl4-independent mechanism."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "J Biol Chem (2010)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1074/jbc.M110.131649"}], "href": "https://doi.org/10.1074/jbc.M110.131649"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "20702414"}], "href": "https://pubmed.ncbi.nlm.nih.gov/20702414"}]}, {"type": "r", "ref": 6, "children": [{"type": "t", "text": "Grzegorz Dobrynin, Oliver Popp, Tina Romer, et al. 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