• DOI:10.1126/science.1179044
• Corpus ID: 206522454

Abundance of Ribosomal RNA Gene Copies Maintains Genome Integrity

@article{Ide2010AbundanceOR,
  title={Abundance of Ribosomal RNA Gene Copies Maintains Genome Integrity},
  author={Satoru Ide and Takaaki Miyazaki and Hisaji Maki and Takehiko Kobayashi},
  journal={Science},
  year={2010},
  volume={327},
  pages={693 - 696}
}

• Satoru Ide, T. Miyazaki, +1 author Takehiko Kobayashi
• Published 5 February 2010
• Biology
• Science

Protective Abundance Massively repeated sequences are generally dangerous to genomes because they promote recombination and, potentially, genome instability. Eukaryotic ribosomal RNA genes (rDNA), which are highly transcribed, are organized into large arrays of repeats and have a system that actively maintains these large arrays. In getting to the bottom of this apparent contradiction, Ide et al. (p. 693) found that reducing the number of rDNA repeats in yeast resulted in a marked sensitivity to DNA damage, owing to heavy rDNA transcription preventing repair of compromised DNA replication forks. It appears that the additional copies of rDNA both reduce the ability of transcription to interfere with DNA repair and provide, through the action of condensin, templates for the recombination-based repair of replication-induced damage. In eukaryotes, multiple copies of ribosomal DNA protect it from transcription-induced replication damage. The ribosomal RNA (rDNA) gene repeats are essential housekeeping genes found in all organisms. A gene amplification system maintains large cluster(s) of tandemly repeated copies in the chromosome, with each species having a specific number of copies. Yeast has many untranscribed rDNA copies (extra copies), and we found that when they are lost, the cells become sensitive to DNA damage induced by mutagens. We show that this sensitivity is dependent on rDNA transcriptional activity, which interferes with cohesion between rDNA loci of sister chromatids. The extra rDNA copies facilitate condensin association and sister-chromatid cohesion, thereby facilitating recombinational repair. These results suggest that high concentrations of heavily transcribed genes are toxic to the cells, and therefore amplified genes, such as rDNA, have evolved.