Division of Molecular Biology of the Cell II, German Cancer Research Center, DKFZ-ZMBH-Alliance, INF 581, 69120 Heidelberg, Germany.
EMBO Rep. 2010 Jan;11(1):52-8. doi: 10.1038/embor.2009.254. Epub 2009 Dec 4.
Epigenetic silencing of a fraction of ribosomal DNA (rDNA) requires association of the nucleolar chromatin-remodelling complex NoRC to 150-250 nucleotide RNAs (pRNA) that originate from an RNA polymerase I promoter located in the intergenic spacer separating rDNA repeats. Here, we show that NoRC-associated pRNA is transcribed from a sub-fraction of hypomethylated rRNA genes during mid S phase, acting in trans to inherit DNA methylation and transcriptional repression of late-replicating silent rDNA copies. The results reveal variability between individual rDNA clusters with distinct functional consequences.
核糖体 DNA(rDNA)的部分基因的表观遗传沉默需要核仁染色质重塑复合物 NoRC 与源自位于 rDNA 重复序列之间的基因间隔区的 RNA 聚合酶 I 启动子的 150-250 个核苷酸 RNA(pRNA)结合。在这里,我们表明 NoRC 相关的 pRNA 是在 S 期中期从亚甲基化的 rRNA 基因的一小部分转录而来的,在转录时可以将 DNA 甲基化和晚期复制的沉默 rDNA 拷贝的转录抑制作用传递下去。结果揭示了个体 rDNA 簇之间的可变性,具有不同的功能后果。