Stowers Institute for Medical Research, Kansas City, MO, USA.
Department of Biochemistry and Molecular Biology, University of Kansas Medical Center, Kansas City, KS, USA.
Results Probl Cell Differ. 2022;70:551-580. doi: 10.1007/978-3-031-06573-6_19.
Eukaryotic genomes maintain multiple copies of ribosomal DNA gene repeats in tandem arrays to provide sufficient ribosomal RNAs to make ribosomes. These DNA repeats are the most highly transcribed regions of the genome, with dedicated transcriptional machinery to manage the enormous task of producing more than 50% of the total RNA in a proliferating cell. The arrays are called nucleolar organizer regions (NORs) and constitute the scaffold of the nucleolar compartment, where ribosome biogenesis occurs. Advances in molecular and cellular biology have brought great insights into how these arrays are transcribed and organized within genomes. Much of their biology is driven by their high transcription level, which has also driven the development of unique methods to understand rDNA gene activity, beginning with classic techniques such as silver staining and Miller spreads. However, the application of modern methodologies such as CRISPR gene editing, super-resolution microscopy, and long-read sequencing has enabled recent advances described herein, with many more discoveries possible soon. This chapter highlights what is known about NOR transcription and organization and the techniques applied historically and currently. Given the potential for NORs to impact organismal health and disease, as highlighted at the end of the chapter, the field must continue to develop and apply innovative analysis to understand genetic, epigenetic, and organizer properties of the ribosomal DNA repeats.
真核生物基因组以串联重复的方式维持多个核糖体 DNA 基因重复拷贝，以提供足够的核糖体 RNA 来合成核糖体。这些 DNA 重复序列是基因组中转录最活跃的区域，具有专门的转录机制来管理在增殖细胞中产生超过 50%总 RNA 的艰巨任务。这些重复序列被称为核仁组织者区域（NORs），构成核仁区室的支架，核糖体生物发生在此发生。分子和细胞生物学的进展为我们深入了解这些基因如何在基因组中被转录和组织提供了重要的见解。它们的生物学特性很大程度上是由其高转录水平驱动的，这也推动了开发独特的方法来理解 rDNA 基因活性的发展，这些方法始于经典技术，如银染和 Miller 铺片。然而，诸如 CRISPR 基因编辑、超分辨率显微镜和长读测序等现代方法学的应用使得本文所描述的最新进展成为可能，并且很快就会有更多的发现。本章重点介绍了关于 NOR 转录和组织的已知内容，以及历史上和当前应用的技术。鉴于 NOR 对生物体健康和疾病的潜在影响，如本章结尾所强调的，该领域必须继续开发和应用创新分析方法来理解核糖体 DNA 重复序列的遗传、表观遗传和组织者特性。
