{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\nNucleostemin – a nucleolar GTP‐binding protein predominantly found in embryonic and tissue stem cells as well as in cancer cells – is critical for early embryogenesis and for maintaining rapid cell cycle progression. Genetic ablation of nucleostemin leads to arrest before or during the blastula stage, while even a partial loss (haploinsufficiency) in mouse embryonic fibroblasts impairs proliferation and accelerates senescence. In contrast, overexpression can rescue these defects and actively promote rapid transit through G1, thereby sustaining stem and progenitor cell self‐renewal and fundamental aspects of early development."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "5"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nIn addition to its role as a cell cycle–promoting factor, nucleostemin safeguards genome integrity. In several experimental settings its depletion provokes replication‐dependent DNA damage, at least in part by impairing the recruitment of key repair proteins such as RAD51, while also interfering with telomere length regulation through interactions with telomeric repeat–binding factors and telomerase components. These functions appear to contribute not only to the maintenance of normal stem cell proliferation, but also to the oncogenic transformation process – for instance, by enhancing tumor initiating cell properties, inducing resistance to genotoxic stress, and even operating in a p53‐independent manner."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "6", "end_ref": "11"}]}, {"type": "t", "text": "\n"}]}, {"type": "t", "text": "\n\n"}, {"type": "p", "children": [{"type": "t", "text": "\nNucleostemin expression is itself subject to tight regulation by oncogenic and metabolic cues. For example, c-Myc directly activates its transcription, while intracellular GTP levels and redox conditions modulate its stability and subcellular localization through unusual, ubiquitin-independent degradation mechanisms. Beyond the stem cell niche, nucleostemin functions in tissue regeneration – as seen in the liver, breast, heart, and testis – where it helps drive proliferation, preserve telomere integrity, and prevent senescence. These multifaceted roles underline its significance both as a regulator of cell proliferation in normal development and as a contributor to tumor progression, making it an attractive potential therapeutic target."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "12", "end_ref": "19"}]}, {"type": "t", "text": "\n"}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Joan C Ritland Politz, Ilvin Polena, Ian Trask, et al. 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