Pre-rRNA Facilitates TopBP1-Mediated DNA Double-Strand Break Response

Area of Science:

• Molecular Biology
• Cellular Biology
• Genetics

Background:

• TopBP1 is crucial for ATR activation in response to DNA damage.
• The precise molecular mechanism of TopBP1's role in DNA repair is not fully understood.

Purpose of the Study:

• To elucidate the molecular mechanism of TopBP1's function in DNA damage response.
• To investigate the association of TopBP1 with other cellular components during genotoxic stress.

Main Methods:

• Unbiased protein affinity purification and RNA sequencing were employed.
• Immunofluorescence microscopy was used to visualize co-localization at DNA double-strand breaks (DSBs).
• RNA polymerase I inhibition was utilized to study pre-ribosomal RNA (pre-rRNA) biogenesis impact.

Main Results:

• TopBP1 was found to associate with pre-ribosomal RNA (pre-rRNA) and co-localize at DSBs.
• Recruitment of TopBP1 to DSBs was dependent on pre-rRNA biogenesis.
• TopBP1's BRCT4-5 domain recognizes pre-rRNA, facilitating liquid-liquid phase separation (LLPS) at DSBs.
• Inhibition of pre-rRNA synthesis impaired TopBP1-mediated cell cycle checkpoint activation and homologous recombination repair.

Conclusions:

• Pre-ribosomal RNA (pre-rRNA) is a key component in the TopBP1-dependent DNA damage response pathway.
• TopBP1's interaction with pre-rRNA, potentially via LLPS, is critical for its recruitment and function at DSBs.
• Pre-rRNA biogenesis is essential for efficient DNA damage signaling and repair mediated by TopBP1.