Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON Canada.
Nucleus. 2012 Jul 1;3(4):315-9. doi: 10.4161/nucl.20585. Epub 2012 Jun 12.
The nucleolus is organized around a scaffolding of rDNA tandem repeats. These repeats, known as ribosomal cassettes, are each composed of ribosomal RNA (rRNA) genes preceding a long intergenic spacer (IGS) that has been classically perceived to be transcriptionally silent. Recent study of the IGS has contradicted the dogma that these spacers are merely inert regions of the genome, instead suggesting they are biologically significant, complex and plurifunctional transcriptional units that appear central to proper cellular functioning. Through the timely induction of various ribosomal IGS noncoding RNA (IGS RNA) transcripts, the cell is capable of both regulating rRNA synthesis and sequestering large numbers of proteins, thereby modulating essential molecular networks. Here we discuss our current understanding of the organization and function of the IGS.
核仁是围绕着 rDNA 串联重复序列的支架组织起来的。这些重复序列，被称为核糖体盒，每个重复序列都由核糖体 RNA（rRNA）基因组成，前面是一个长的基因间间隔区（IGS），IGS 传统上被认为是转录沉默的。最近对 IGS 的研究反驳了这样一种观点，即这些间隔区仅仅是基因组的无活性区域，相反，它们被认为是具有生物学意义的、复杂的和多功能的转录单位，这些单位似乎对细胞的正常功能至关重要。通过适时诱导各种核糖体 IGS 非编码 RNA（IGS RNA）转录本，细胞能够同时调节 rRNA 的合成和隔离大量蛋白质，从而调节重要的分子网络。在这里，我们讨论我们对 IGS 的组织和功能的现有认识。
