The nucleolus is the largest sub-nuclear domain, serving primarily as the place for ribosome biogenesis. A delicately regulated function of the nucleolus is vital to the cell not only for maintaining proper protein synthesis but is also tightly associated with responses to different types of cellular stresses. Recently, several long non-coding RNAs (lncRNAs) were found to be part of the regulatory network that modulate nucleolar functions. Several of these lncRNAs are encoded in the ribosomal DNA (rDNA) repeats or are transcribed from the genomic regions that are located near the nucleolus organizer regions (NORs). In this review, we first discuss the current understanding of the sequence of the NORs and variations between different NORs. We then focus on the NOR-derived lncRNAs in mammalian cells and their functions in rRNA transcription and the organization of nucleolar structure under different cellular conditions. The identification of these lncRNAs reveals great potential of the NORs in harboring novel genes involved in the regulation of nucleolar functions.

核仁是最大的亚核结构域，主要用作核糖体生物发生的场所。核仁的精细调节功能对细胞至关重要，不仅对于维持适当的蛋白质合成，而且与对不同类型细胞应激的反应密切相关。最近，发现几种长链非编码 RNA (lncRNA) 是调节核仁功能的调控网络的一部分。其中一些 lncRNA 在核糖体 DNA (rDNA) 重复序列中编码或从位于核仁组织区 (NOR) 附近的基因组区域转录。在这篇综述中，我们首先讨论了目前对 NOR 序列的理解以及不同 NOR 之间的变化。然后，我们关注哺乳动物细胞中 NOR 衍生的 lncRNA 及其在 rRNA 转录中的功能以及不同细胞条件下核仁结构的组织。这些 lncRNA 的鉴定揭示了 NOR 在包含参与核仁功能调节的新基因方面的巨大潜力。