Saccharomyces cerevisiae ribosomal DNA, the repeated region where rRNAs are synthesized by about 150 encoding units, hosts all the protein machineries responsible for the main DNA transactions such as replication, transcription and recombination. This and its repetitive nature make rDNA a unique and complex genetic locus compared to any other. All the different molecular machineries acting in this locus need to be accurately and finely controlled and coordinated and for this reason rDNA is one of the most impressive examples of highly complex molecular regulated loci. The region in which the large molecular complexes involved in rDNA activity and/or regulation are recruited is extremely small: that is, the 2.5 kb long intergenic spacer, interrupting each 35S RNA coding unit from the next. All S. cerevisiae RNA polymerases (I, II and III) transcribing the different genetic rDNA elements are recruited here; a sequence responsible for each rDNA unit replication, which needs its molecular apparatus, also localizes here; moreover, it is noteworthy that the rDNA replication proceeds almost unidirectionally because each replication fork is stopped in the so-called replication fork barrier. These localized fork blocking events induce, with a given frequency, the homologous recombination process by which cells maintain a high identity among the rDNA repeated units. Here, we describe the different processes involving the rDNA locus, how they influence each other and how these mutual interferences are highly regulated and coordinated. We propose that an rDNA conformation as a super-hub could help in optimizing the micro-environment for all basic DNA transactions.

酿酒酵母核糖体 DNA 是由约 150 个编码单元合成 rRNA 的重复区域，承载着负责主要 DNA 事务（例如复制、转录和重组）的所有蛋白质机器。与任何其他基因位点相比，这一点及其重复性使 rDNA 成为独特且复杂的基因位点。作用于该基因座的所有不同分子机器都需要精确、精细的控制和协调，因此 rDNA 是高度复杂的分子调控基因座最令人印象深刻的例子之一。参与 rDNA 活性和/或调节的大分子复合物被招募的区域非常小：即 2.5 kb 长的基因间隔区，将每个 35S RNA 编码单元与下一个编码单元打断。所有转录不同遗传 rDNA 元件的酿酒酵母RNA 聚合酶（I、II 和 III）均在此招募；负责每个 rDNA 单元复制的序列（需要其分子装置）也位于此处；此外，值得注意的是，rDNA复制几乎是单向进行的，因为每个复制叉都在所谓的复制叉屏障中停止。这些局部叉阻断事件以给定的频率诱导同源重组过程，细胞通过该过程在 rDNA 重复单元中保持高度同一性。在这里，我们描述了涉及 rDNA 位点的不同过程、它们如何相互影响以及这些相互干扰如何被高度调控和协调。我们认为 rDNA 构象作为超级中心可以帮助优化所有基本 DNA 交易的微环境。