{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nA series of studies investigating the mammalian N‐end rule pathway have revealed that E3 ubiquitin ligases—particularly UBR2, a homolog of UBR1—play indispensable roles in the recognition and degradation of proteins carrying destabilizing N‐terminal residues. UBR2 functions in critical developmental processes including embryogenesis, male meiosis, and pancreatic and neurogenic development, as demonstrated by analyses in various knockout mouse models. These findings underscore that proper regulation of protein turnover via the N‐end rule pathway is essential for tissue homeostasis and normal organismal development."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "3"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nAdditional investigations have further delineated the multifaceted roles of UBR2 beyond conventional proteolytic targeting. In mouse spermatocytes, UBR2 is involved in chromatin remodeling through histone H2A ubiquitination, thereby mediating transcriptional silencing over unsynapsed chromosomal regions during meiosis. Moreover, UBR2 forms a stabilizing complex with the germ cell–specific protein Tex19.1, and its absence correlates with impaired chromosomal synapsis, genome instability, and defects in homologous recombination repair. Together, these studies illustrate that UBR2 is a key coordinator of both chromatin dynamics and genomic integrity."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "4", "end_ref": "7"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nFurthermore, in pathogenic contexts, UBR2 has been implicated in processes that contribute to disease progression. In models of cancer cachexia, UBR2 up‐regulation drives the selective ubiquitination and degradation of fast‐twitch myosin heavy chain isoforms, thereby promoting muscle wasting. In parallel, studies involving p53‐deficient mesenchymal stem cells indicate that UBR2 can be packaged into exosomes that, upon transfer to target cells, potentiate tumor growth and metastasis via modulation of the Wnt/β‐catenin pathway. These observations highlight UBR2’s diverse roles in both physiological homeostasis and disease-related proteolytic events."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "8", "end_ref": "10"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nIt is important to note that although the original query requested a summary regarding OR52E1, none of the provided abstracts contain any information about OR52E1. Instead, the available studies focus on the functions of ubiquitin ligases such as UBR2 and their roles in protein degradation, chromatin regulation, genomic stability, and disease processes.\n"}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Yong Tae Kwon, Zanxian Xia, Jee Young An, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Female lethality and apoptosis of spermatocytes in mice lacking the UBR2 ubiquitin ligase of the N-end rule pathway."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Mol Cell Biol (2003)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1128/MCB.23.22.8255-8271.2003"}], "href": "https://doi.org/10.1128/MCB.23.22.8255-8271.2003"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "14585983"}], "href": "https://pubmed.ncbi.nlm.nih.gov/14585983"}]}, {"type": "r", "ref": 2, "children": [{"type": "t", "text": "Jaana Niittymäki, Pirkko Mattila, Christophe Roos, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Cloning and expression of murine enzymes involved in the salvage pathway of GDP-L-fucose."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Eur J Biochem (2004)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1046/j.1432-1033.2003.03904.x"}], "href": "https://doi.org/10.1046/j.1432-1033.2003.03904.x"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "14686921"}], "href": "https://pubmed.ncbi.nlm.nih.gov/14686921"}]}, {"type": "r", "ref": 3, "children": [{"type": "t", "text": "Jee Young An, Jai Wha Seo, Takafumi Tasaki, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Impaired neurogenesis and cardiovascular development in mice lacking the E3 ubiquitin ligases UBR1 and UBR2 of the N-end rule pathway."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Proc Natl Acad Sci U S A (2006)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1073/pnas.0601700103"}], "href": "https://doi.org/10.1073/pnas.0601700103"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "16606826"}], "href": "https://pubmed.ncbi.nlm.nih.gov/16606826"}]}, {"type": "r", "ref": 4, "children": [{"type": "t", "text": "Yan Ouyang, Yong Tae Kwon, Jee Young An, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Loss of Ubr2, an E3 ubiquitin ligase, leads to chromosome fragility and impaired homologous recombinational repair."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Mutat Res (2006)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1016/j.mrfmmm.2005.12.016"}], "href": "https://doi.org/10.1016/j.mrfmmm.2005.12.016"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "16488448"}], "href": "https://pubmed.ncbi.nlm.nih.gov/16488448"}]}, {"type": "r", "ref": 5, "children": [{"type": "t", "text": "Jee Young An, Eun-A Kim, Yonghua Jiang, et al. "}, {"type": "b", "children": [{"type": "t", "text": "UBR2 mediates transcriptional silencing during spermatogenesis via histone ubiquitination."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Proc Natl Acad Sci U S A (2010)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1073/pnas.0910267107"}], "href": "https://doi.org/10.1073/pnas.0910267107"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "20080676"}], "href": "https://pubmed.ncbi.nlm.nih.gov/20080676"}]}, {"type": "r", "ref": 6, "children": [{"type": "t", "text": "Fang Yang, Yong Cheng, Jee Young An, et al. "}, {"type": "b", "children": [{"type": "t", "text": "The ubiquitin ligase Ubr2, a recognition E3 component of the N-end rule pathway, stabilizes Tex19.1 during spermatogenesis."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "PLoS One (2010)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1371/journal.pone.0014017"}], "href": "https://doi.org/10.1371/journal.pone.0014017"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "21103378"}], "href": "https://pubmed.ncbi.nlm.nih.gov/21103378"}]}, {"type": "r", "ref": 7, "children": [{"type": "t", "text": "James H Crichton, Christopher J Playfoot, Marie MacLennan, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Tex19.1 promotes Spo11-dependent meiotic recombination in mouse spermatocytes."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "PLoS Genet (2017)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1371/journal.pgen.1006904"}], "href": "https://doi.org/10.1371/journal.pgen.1006904"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "28708824"}], "href": "https://pubmed.ncbi.nlm.nih.gov/28708824"}]}, {"type": "r", "ref": 8, "children": [{"type": "t", "text": "Guohua Zhang, Ren-Kuo Lin, Yong Tae Kwon, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Signaling mechanism of tumor cell-induced up-regulation of E3 ubiquitin ligase UBR2."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "FASEB J (2013)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1096/fj.12-222711"}], "href": "https://doi.org/10.1096/fj.12-222711"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "23568773"}], "href": "https://pubmed.ncbi.nlm.nih.gov/23568773"}]}, {"type": "r", "ref": 9, "children": [{"type": "t", "text": "Jiahui Mao, Zhaofeng Liang, Bin Zhang, et al. "}, {"type": "b", "children": [{"type": "t", "text": "UBR2 Enriched in p53 Deficient Mouse Bone Marrow Mesenchymal Stem Cell-Exosome Promoted Gastric Cancer Progression via Wnt/β-Catenin Pathway."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Stem Cells (2017)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1002/stem.2702"}], "href": "https://doi.org/10.1002/stem.2702"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "28895255"}], "href": "https://pubmed.ncbi.nlm.nih.gov/28895255"}]}, {"type": "r", "ref": 10, "children": [{"type": "t", "text": "Song Gao, Guohua Zhang, Zicheng Zhang, et al. "}, {"type": "b", "children": [{"type": "t", "text": "UBR2 targets myosin heavy chain IIb and IIx for degradation: Molecular mechanism essential for cancer-induced muscle wasting."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Proc Natl Acad Sci U S A (2022)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1073/pnas.2200215119"}], "href": "https://doi.org/10.1073/pnas.2200215119"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "36252004"}], "href": "https://pubmed.ncbi.nlm.nih.gov/36252004"}]}]}]}