{"type": "root", "children": [{"type": "p", "children": [{"type": "t", "text": "\n Dicer1 is a pivotal RNase III–type enzyme that functions at the heart of RNA‐mediated gene regulation. In the cytoplasm it cleaves approximately 70‐nucleotide precursor microRNAs (pre‐miRNAs) into mature ~22‐nucleotide miRNAs possessing characteristic 3′ overhangs, which then guide the RNA‐induced silencing complex (RISC) to target mRNAs for translational repression or destabilization."}, {"type": "fg", "children": [{"type": "fg_fs", "start_ref": "1", "end_ref": "3"}]}, {"type": "t", "text": " Structural studies have shown that Dicer1 operates via intramolecular dimerization of its two RNase III domains, a process aided by its PAZ and RNA binding domains, to ensure precise cleavage of its dsRNA substrates.\n "}]}, {"type": "t", "text": "\n "}, {"type": "p", "children": [{"type": "t", "text": "\n Functional disruption of Dicer1 in mice has underscored its critical role in early development and stem cell maintenance. Genetic ablation of Dicer1 results in embryonic lethality accompanied by depletion of multipotent stem cells and profound defects in differentiation."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "4"}]}, {"type": "t", "text": " In addition to processing canonical miRNAs, Dicer1 is essential for generating small interfering RNAs (siRNAs) from long double‐stranded RNAs and has been implicated in the biogenesis of noncanonical small RNAs derived from substrates such as small nucleolar RNAs."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "6"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n "}, {"type": "p", "children": [{"type": "t", "text": "\n Moreover, conditional inactivation studies in diverse tissues—including studies in endothelial cells and developing limb mesoderm—demonstrate that Dicer1 loss compromises cell proliferation, survival, and overall tissue morphogenesis."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "7"}]}, {"type": "t", "text": " In pathological contexts, reduced Dicer1 expression has been associated with impaired RNA interference efficiency and aberrant gene regulation; for example, low Dicer1 levels in ovarian cancer cells correlate with poor clinical outcomes and may hinder effective shRNA‐mediated gene silencing."}, {"type": "fg", "children": [{"type": "fg_f", "ref": "9"}]}, {"type": "t", "text": "\n "}]}, {"type": "t", "text": "\n "}, {"type": "p", "children": [{"type": "t", "text": "\n Collectively, these studies illuminate Dicer1 as an indispensable enzyme that ensures proper miRNA and siRNA biogenesis, thereby orchestrating critical developmental processes, maintaining stem cell function, and safeguarding normal cellular homeostasis. Its central role in the RNA interference pathway renders it a key factor in both physiological gene regulation and the pathogenesis of human diseases.\n "}]}, {"type": "rg", "children": [{"type": "r", "ref": 1, "children": [{"type": "t", "text": "Yoontae Lee, Chiyoung Ahn, Jinju Han, et al. "}, {"type": "b", "children": [{"type": "t", "text": "The nuclear RNase III Drosha initiates microRNA processing."}]}, {"type": "t", "text": " "}, {"type": "i", "children": [{"type": "t", "text": "Nature (2003)"}]}, {"type": "t", "text": " DOI: "}, {"type": "a", "children": [{"type": "t", "text": "10.1038/nature01957"}], "href": "https://doi.org/10.1038/nature01957"}, {"type": "t", "text": " PMID: "}, {"type": "a", "children": [{"type": "t", "text": "14508493"}], "href": "https://pubmed.ncbi.nlm.nih.gov/14508493"}]}, {"type": "r", "ref": 2, "children": [{"type": "t", "text": "Jinju Han, Yoontae Lee, Kyu-Hyun Yeom, et al. 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