AI Article Synopsis

  • * In healthy cells, the homologous recombination (HR) process for rDNA stability is similar to that in other parts of the genome but is disrupted in BLM-deficient cells.
  • * Without Bloom helicase (BLM), rDNA can still attract RAD51, which causes genomic instability and micronuclei formation, indicating broader implications for genome integrity.

Article Abstract

Ribosomal DNA (rDNA) encodes the ribosomal RNA genes and represents an intrinsically unstable genomic region. However, the underlying mechanisms and implications for genome integrity remain elusive. Here, we use Bloom syndrome (BS), a rare genetic disease characterized by DNA repair defects and hyper-unstable rDNA, as a model to investigate the mechanisms leading to rDNA instability. We find that in Bloom helicase (BLM) proficient cells, the homologous recombination (HR) pathway in rDNA resembles that in nuclear chromatin; it is initiated by resection, replication protein A (RPA) loading and BRCA2-dependent RAD51 filament formation. However, BLM deficiency compromises RPA-loading and BRCA1/2 recruitment to rDNA, but not RAD51 accumulation. RAD51 accumulates at rDNA despite depletion of long-range resection nucleases and rDNA damage results in micronuclei when BLM is absent. In summary, our findings indicate that rDNA is permissive to RAD51 accumulation in the absence of BLM, leading to micronucleation and potentially global genomic instability.

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http://www.ncbi.nlm.nih.gov/pmc/articles/PMC11379943PMC
http://dx.doi.org/10.1038/s41467-024-52189-6DOI Listing

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