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Nucleolar reorganization in response to rDNA damage
Marjolein van Sluis1, Brian McStay1
1Centre for Chromosome Biology, School of Natural Sciences, National University of Ireland Galway, Ireland.
Current Opinion in Cell Biology
|April 22, 2017
Summary
DNA double-strand breaks (DSBs) in ribosomal DNA (rDNA) trigger nucleolar reorganization, moving rDNA to the periphery for repair. This process involves ATM-dependent transcription inhibition and recruits homologous recombination (HR) factors.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Nucleoli are essential for ribosome biogenesis, forming around nucleolar organizer regions (NORs) containing ribosomal DNA (rDNA) arrays.
- NORs represent highly transcribed, repetitive genomic loci crucial for cellular function.
- Investigating the DNA double-strand break (DSB) response at NORs offers insights into genome stability at essential genetic sites.
Purpose of the Study:
- To investigate the cellular response to targeted DNA double-strand breaks (DSBs) within ribosomal DNA (rDNA) loci.
- To elucidate the mechanisms of nucleolar reorganization and DNA repair at NORs following DSB induction.
- To explore the role of ATM kinase and homologous recombination (HR) in repairing rDNA DSBs.
Main Methods:
- Targeted introduction of DSBs into rDNA arrays within human cells.
- Analysis of RNA-polymerase I transcription inhibition.
- Microscopy techniques to observe nucleolar structure and rDNA localization.
- Assessment of DNA repair factor recruitment and homologous recombination (HR) machinery engagement.
Main Results:
- ATM-dependent inhibition of RNA-polymerase I transcription occurred following rDNA DSBs.
- Induced DSBs caused nucleolar reorganization, with rDNA moving from the interior to the periphery.
- Nucleolar reorganization increased accessibility of rDNA to repair factors.
- Accurate homologous recombination (HR) repair machinery was recruited to rDNA DSBs throughout the cell cycle, suggesting in cis templating.
Conclusions:
- Stress-induced nucleolar reorganization facilitates the repair of DNA double-strand breaks at essential rDNA loci.
- Homologous recombination (HR) is a key repair pathway for rDNA DSBs and can be templated in cis.
- Understanding nucleolar biophysics and stress responses is crucial for comprehending genome maintenance.
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