{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nSMG1 is a phosphatidylinositol 3‐kinase–related kinase (PIKK) best known for its pivotal role in nonsense‐mediated mRNA decay (NMD). It phosphorylates the RNA helicase UPF1 upon association with exon junction complexes and other translation termination factors, forming a transient surveillance assembly (the SURF complex) that couples premature termination codon recognition with mRNA degradation. These studies have established SMG1 as essential for transcriptome quality control and proper regulation of mRNA surveillance pathways."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "3"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nIn addition to its role in NMD, SMG1 functions as a stress‐responsive kinase within the DNA damage response. It mediates rapid phosphorylation of proteins such as p53 and other substrates at serine/threonine–glutamine motifs in response to genotoxic insults, thereby contributing to cell cycle checkpoint regulation. Structural and mutational analyses reveal that distinct domains of SMG1—including its extensive N‐terminal region and FATC domain—are indispensable for its kinase activity, offering insights into its substrate specificity and activation dynamics during cellular stress. Furthermore, SMG1 has been implicated in modulating stress granule assembly, underscoring its broader role in coordinating cellular responses to damage."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "4", "end_ref": "9"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nEmerging evidence also highlights SMG1’s tumor suppressor activity and its involvement in oncogenic signaling. Its expression and activity can be attenuated by promoter hypermethylation or targeted by specific microRNAs, leading to impaired stress responses and cell cycle control that predispose to neoplastic transformation in diverse contexts such as human papillomavirus–associated head and neck cancer, gastric cancer, and acute myeloid leukemia. Recent high‐resolution cryo–electron microscopy studies of SMG1 complexes with its cofactors SMG8 and SMG9, along with bound regulatory molecules like inositol hexaphosphate, have illuminated the molecular basis for substrate recognition and the allosteric modulation of its kinase activity, underscoring the therapeutic relevance of SMG1 modulation in cancer and other stress‐related pathologies."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "10", "end_ref": "16"}]}, {"type": "t", "text": "\n"}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Robert T Abraham "}, {"type": "b", "children": [{"type": "t", "text": "The ATM-related kinase, hSMG-1, bridges genome and RNA surveillance pathways."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "DNA Repair (Amst) (2004)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1016/j.dnarep.2004.04.003"}], "href": "https://doi.org/10.1016/j.dnarep.2004.04.003"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "15279777"}], "href": "https://pubmed.ncbi.nlm.nih.gov/15279777"}]}, {"type": "r", "ref": 2, "children": [{"type": "t", "text": "Isao Kashima, Akio Yamashita, Natsuko Izumi, et al. "}, {"type": "b", "children": [{"type": "t", "text": "Binding of a novel SMG-1-Upf1-eRF1-eRF3 complex (SURF) to the exon junction complex triggers Upf1 phosphorylation and nonsense-mediated mRNA decay."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Genes Dev (2006)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1101/gad.1389006"}], "href": "https://doi.org/10.1101/gad.1389006"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "16452507"}], "href": "https://pubmed.ncbi.nlm.nih.gov/16452507"}]}, {"type": "r", "ref": 3, "children": [{"type": "t", "text": "Akio Yamashita, Natsuko Izumi, Isao Kashima, et al. "}, {"type": "b", "children": [{"type": "t", "text": "SMG-8 and SMG-9, two novel subunits of the SMG-1 complex, regulate remodeling of the mRNA surveillance complex during nonsense-mediated mRNA decay."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Genes Dev (2009)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1101/gad.1767209"}], "href": "https://doi.org/10.1101/gad.1767209"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "19417104"}], "href": "https://pubmed.ncbi.nlm.nih.gov/19417104"}]}, {"type": "r", "ref": 4, "children": [{"type": "t", "text": "Tomoko Morita, Akio Yamashita, Isao Kashima, et al. 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