{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\n COP1 (constitutive photomorphogenesis protein 1, also known as RFWD2) is an E3 ubiquitin ligase that orchestrates protein turnover by marking specific substrates for proteasomal degradation. A series of studies show that COP1 plays a central role in multiple biological contexts. In several cancer models, COP1 acts as a tumor suppressor by targeting oncogenic transcription factors for degradation. For example, it ubiquitinates members of the ETS family (such as ETV1, ETV4, ETV5, and ETS2) as well as the oncoprotein c‐Jun, thereby dampening transcriptional programs that drive cell proliferation and tumor progression."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "4"}]}, {"type": "t", "text": " In triple‐negative breast cancer, decreased COP1 levels correlate with elevated ETV1 and a more aggressive phenotype."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "5"}]}, {"type": "t", "text": " Moreover, in hepatic and gastric cancers, aberrant COP1 expression has been linked to the disruption of p53 signaling, with COP1 targeting p53 for degradation."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "6", "end_ref": "8"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n The functional importance of COP1 extends beyond tumorigenesis. In developmental contexts such as lung morphogenesis, COP1-mediated degradation of ETS factors is critical for proper epithelial branching."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "3"}]}, {"type": "t", "text": " In the nervous system, COP1 helps maintain proteostasis in microglia by limiting the accumulation of the pro-inflammatory transcription factor C/EBPβ, thereby suppressing neuroinflammatory and neurodegenerative cascades."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "9"}]}, {"type": "t", "text": ""}]}, {"type": "t", "text": "\n \n "}, {"type": "p", "children": [{"type": "t", "text": "\n Furthermore, COP1 participates in broader regulatory networks through its interactions with other proteins. Its association with factors such as the pseudokinase STK40 underlines its role as an adaptor in ubiquitin-mediated signaling."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "10"}]}, {"type": "t", "text": " Collectively, these findings establish COP1 as an integrative node that governs key cellular processes—including tumor suppression, developmental patterning, and inflammatory responses—by modulating the stability of pivotal regulatory proteins.\n "}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Alberto C Vitari, Kevin G Leong, Kim Newton, et al. 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