{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nPJA1 is a RING finger E3 ubiquitin ligase that plays multifaceted roles in regulating protein stability in diverse biological processes. In bone and neural development, PJA1 targets key regulatory proteins for ubiquitination‐dependent degradation. For example, it binds to Dlxin‑1—thereby modulating Dlx5‐dependent transcription during osteoblast differentiation—and is abundantly expressed throughout the brain where it interacts with ubiquitin conjugating enzymes, raising its candidacy for X‑linked mental retardation. Moreover, PJA1 directly ubiquitinates components of the polycomb repressive complex 2 (PRC2), leading to the proteasomal degradation of its subunits and consequently influencing developmental gene repression"}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "3"}]}, {"type": "t", "text": "<br><br>\nIn neurodegenerative contexts, PJA1 contributes to cellular proteostasis by targeting aggregation‐prone proteins. It binds the C‑terminal fragment of TDP‑43 and suppresses its phosphorylation and aggregate formation—mechanisms that are relevant to amyotrophic lateral sclerosis (ALS) and frontotemporal lobar degeneration (FTLD). In addition, PJA1 enhances the degradation of mutant polyglutamine proteins (such as those implicated in Huntington’s disease and spinocerebellar ataxia type 3), thereby reducing the accumulation of toxic aggregates. Although not described in detail, emerging analyses also associate PJA1 with neurodevelopmental disorders"}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "4", "end_ref": "6"}]}, {"type": "t", "text": "<br><br>\nIn cancer, PJA1 exhibits context‐dependent roles by modulating critical signaling pathways via targeted protein degradation. It promotes ubiquitination and degradation of phosphorylated SMAD3, thus impairing SMAD3/β2SP‑dependent tumor suppressor activity in hepatocellular carcinoma. In lung adenocarcinoma, PJA1 regulates the turnover of FOXR2, leading to inhibited cell invasion and increased apoptosis through attenuation of the Wnt/β‑catenin pathway. Notably, in nasopharyngeal carcinoma, high PJA1 expression confers chemoresistance by degrading the mitochondrial protein PGAM5—thereby suppressing pyroptosis and the associated antitumor immune response. Complementary proteomic studies have further expanded the known substrate repertoire of PJA1, emphasizing its broad regulatory influence via ubiquitin‐mediated degradation."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "7", "end_ref": "10"}]}, {"type": "t", "text": ""}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Aya Sasaki, Yoshiko Masuda, Kazuhiro Iwai, et al. 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"}, {"type": "b", "children": [{"type": "t", "text": "PJA1, encoding a RING-H2 finger ubiquitin ligase, is a novel human X chromosome gene abundantly expressed in brain."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Genomics (2002)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1006/geno.2002.6770"}], "href": "https://doi.org/10.1006/geno.2002.6770"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "12036302"}], "href": "https://pubmed.ncbi.nlm.nih.gov/12036302"}]}, {"type": "r", "ref": 3, "children": [{"type": "t", "text": "Muhammad Zoabi, Ronen Sadeh, Prim de Bie, et al. "}, {"type": "b", "children": [{"type": "t", "text": "PRAJA1 is a ubiquitin ligase for the polycomb repressive complex 2 proteins."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Biochem Biophys Res Commun (2011)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1016/j.bbrc.2011.04.025"}], "href": "https://doi.org/10.1016/j.bbrc.2011.04.025"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "21513699"}], "href": "https://pubmed.ncbi.nlm.nih.gov/21513699"}]}, {"type": "r", "ref": 4, "children": [{"type": "t", "text": "Kazuhiko Watabe, Yoichiro Kato, Miho Sakuma, et al. 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