Department of Histology and Embryology, Medical Faculty, Aydın Adnan Menderes University, Aydın, Turkey.
Department of Basic Oncology and Cancer Biology, Institute of Health Sciences, Aydın Adnan Menderes University, Aydın, Turkey.
Methods Mol Biol. 2022;2257:1-32. doi: 10.1007/978-1-0716-1170-8_1.
MicroRNAs are RNAs of about 18-24 nucleotides in lengths, which are found in the small noncoding RNA class and have a crucial role in the posttranscriptional regulation of gene expression, cellular metabolic pathways, and developmental events. These small but essential molecules are first processed by Drosha and DGCR8 in the nucleus and then released into the cytoplasm, where they cleaved by Dicer to form the miRNA duplex. These duplexes are bound by the Argonaute (AGO) protein to form the RNA-induced silencing complex (RISC) in a process called RISC loading. Transcription of miRNAs, processing with Drosha and DGCR8 in the nucleus, cleavage by Dicer, binding to AGO proteins and forming RISC are the most critical steps in miRNA biogenesis. Additional molecules involved in biogenesis at these stages can enhance or inhibit these processes, which can radically change the fate of the cell. Biogenesis is regulated by many checkpoints at every step, primarily at the transcriptional level, in the nucleus, cytoplasm, with RNA regulation, RISC loading, miRNA strand selection, RNA methylation/uridylation, and turnover rate. Moreover, in recent years, different regulation mechanisms have been discovered in noncanonical Drosha or Dicer-independent pathways. This chapter seeks answers to how miRNA biogenesis and function are regulated through both canonical and non-canonical pathways.
微 RNA 是长度约为 18-24 个核苷酸的 RNA，属于小非编码 RNA 类，在基因表达的转录后调控、细胞代谢途径和发育事件中起着至关重要的作用。这些微小但必不可少的分子首先由 Drosha 和 DGCR8 在核内加工，然后释放到细胞质中，在那里被 Dicer 切割形成 miRNA 双链。这些双链被 Argonaute（AGO）蛋白结合，形成 RNA 诱导沉默复合物（RISC），这一过程称为 RISC 加载。miRNA 的转录、核内 Drosha 和 DGCR8 的加工、Dicer 的切割、AGO 蛋白的结合以及 RISC 的形成是 miRNA 生物发生的最关键步骤。在这些阶段参与生物发生的其他分子可以增强或抑制这些过程，这可能会彻底改变细胞的命运。生物发生受到每个步骤的许多检查点的调节，主要在转录水平、核内、细胞质内、通过 RNA 调节、RISC 加载、miRNA 链选择、RNA 甲基化/尿嘧啶化和周转率。此外，近年来，在非规范 Drosha 或 Dicer 独立途径中发现了不同的调节机制。本章旨在探讨 miRNA 生物发生和功能是如何通过规范和非规范途径进行调节的。
