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Updated: Jun 17, 2026

Single Nucleotide Polymorphism-sensitive FISH Detection of Locus-specific Ribosomal RNA Transcription in Drosophila melanogaster
Published on: March 28, 2025
Intergenic transcripts originating from a subclass of ribosomal DNA repeats silence ribosomal RNA genes in trans
Raffaella Santoro1, Kerstin-Maike Schmitz, Juan Sandoval
1Division of Molecular Biology of the Cell II, German Cancer Research Center, DKFZ-ZMBH-Alliance, INF 581, 69120 Heidelberg, Germany.
Abstract:
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.
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