Alu 反转录转座子属于短散在的核元件 (SINE) 类。Alu RNA 在细胞中含量丰富,其重复结构形成双链 RNA (dsRNA),可激活 dsRNA 传感器并触发具有显着病理后果的先天免疫反应。防止先天免疫激活的机制包括 dsRNA 中的腺苷脱氨基化为肌苷,称为 A-to-I 编辑,内切核糖核酸酶降解 Alu RNA,以及通过 RNA 结合蛋白隔离 Alu RNA。我们之前已经证明,Alu RNA A-to-I 编辑的广泛缺失与多种人类疾病有关,包括病毒性(COVID-19、流感)和自身免疫性疾病(多发性硬化症)。在这里,我们证明白细胞中 A-to-I 编辑的缺失也与炎症性肠病有关。我们的结构-功能分析表明,激活先天免疫反应的能力存在于 Alu RNA 的左臂,需要 5'-PPP,RIG-I 是主要的 Alu dsRNA 传感器,A-to-I 编辑会破坏结构和功能。此外,经过编辑的 Alu RNA 会抑制未经编辑的 Alu RNA 的活性。改变 Alu RNA 核苷酸序列会增加生物活性。存在两类 Alu RNA,一类刺激 IRF 和 NF-kB 转录活性,而第二类仅刺激 IRF 转录活性。因此,Alu RNA 在人类疾病中发挥重要作用,但也可能具有治疗潜力。此外,经过编辑的 Alu RNA 会抑制未经编辑的 Alu RNA 的活性。改变 Alu RNA 核苷酸序列会增加生物活性。存在两类 Alu RNA,一类刺激 IRF 和 NF-kB 转录活性,而第二类仅刺激 IRF 转录活性。因此,Alu RNA 在人类疾病中发挥重要作用,但也可能具有治疗潜力。此外,经过编辑的 Alu RNA 会抑制未经编辑的 Alu RNA 的活性。改变 Alu RNA 核苷酸序列会增加生物活性。存在两类 Alu RNA,一类刺激 IRF 和 NF-kB 转录活性,而第二类仅刺激 IRF 转录活性。因此,Alu RNA 在人类疾病中发挥重要作用,但也可能具有治疗潜力。
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Alu RNA Structural Features Modulate Immune Cell Activation and A-to-I Editing of Alu RNAs Is Diminished in Human Inflammatory Bowel Disease
Alu retrotransposons belong to the class of short interspersed nuclear elements (SINEs). Alu RNA is abundant in cells and its repetitive structure forms double-stranded RNAs (dsRNA) that activate dsRNA sensors and trigger innate immune responses with significant pathological consequences. Mechanisms to prevent innate immune activation include deamination of adenosines to inosines in dsRNAs, referred to as A-to-I editing, degradation of Alu RNAs by endoribonucleases, and sequestration of Alu RNAs by RNA binding proteins. We have previously demonstrated that widespread loss of Alu RNA A-to-I editing is associated with diverse human diseases including viral (COVID-19, influenza) and autoimmune diseases (multiple sclerosis). Here we demonstrate loss of A-to-I editing in leukocytes is also associated with inflammatory bowel diseases. Our structure-function analysis demonstrates that ability to activate innate immune responses resides in the left arm of Alu RNA, requires a 5’-PPP, RIG-I is the major Alu dsRNA sensor, and A-to-I editing disrupts both structure and function. Further, edited Alu RNAs inhibit activity of unedited Alu RNAs. Altering Alu RNA nucleotide sequence increases biological activity. Two classes of Alu RNAs exist, one class stimulates both IRF and NF-kB transcriptional activity and a second class only stimulates IRF transcriptional activity. Thus, Alu RNAs play important roles in human disease but may also have therapeutic potential.