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Two- and Three-Dimensional Live Cell Imaging of DNA Damage Response Proteins
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Two- and Three-Dimensional Live Cell Imaging of DNA Damage Response Proteins

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Dynamic recruitment of licensing factor Cdt1 to sites of DNA damage

Vassilis Roukos1, Ali Kinkhabwala, Julien Colombelli

  • 1Department of General Biology, School of Medicine, University of Patras, 26500 Rio, Patras, Greece.

Journal of Cell Science
|January 13, 2011
PubMed

Insights

Cell cycle regulation requires linking DNA damage responses. Following DNA damage, Cdt1 (cell division cycle 101) rapidly accumulates at damaged sites, dependent on PCNA (proliferating cell nuclear antigen), preceding its degradation.

Area of Science:

  • Molecular Biology
  • Cell Biology
  • Genomics

Background:

  • Genomic integrity relies on the coordinated regulation of the cell cycle and DNA damage response pathways.
  • Cdt1 (cell division cycle 101), a G1-specific cell-cycle regulator, is degraded following DNA damage via the Cul4-Ddb1(Cdt2) ubiquitin ligase.
  • Understanding the spatiotemporal dynamics of Cdt1 recruitment to DNA damage sites is crucial for comprehending cell cycle control and DNA repair.

Purpose of the Study:

  • To investigate the real-time recruitment dynamics of Cdt1 and associated proteins to sites of DNA damage in living G1-phase cells.
  • To elucidate the role of PCNA (proliferating cell nuclear antigen) and Cdt2 in the recruitment and regulation of Cdt1 at DNA damage sites.
  • To characterize the binding kinetics and mobility of Cdt1, PCNA, and Cdt2 at DNA damage foci using quantitative imaging techniques.

Main Methods:

  • Spatially restricted DNA damage induction within living cell nuclei using laser nanosurgery microscopy.
  • Live-cell imaging to monitor the rapid recruitment of fluorescently tagged proteins (Cdt1, PCNA, Cdt2, Cul4, DDB1, p21Cip1) to damage sites.
  • Fluorescence recovery after photobleaching (FRAP) combined with reaction-diffusion modeling to quantify protein dynamics and binding interactions.

Main Results:

  • Cdt1 rapidly accumulates at DNA damage sites within seconds of induction in G1-phase cells.
  • Recruitment of Cdt1 to damage sites is dependent on PCNA, while PCNA and Cdt2 recruitment are independent of Cdt1.
  • FRAP analysis revealed dynamic binding of Cdt1 and p21Cip1 at damage sites, with PCNA exhibiting immobile behavior, suggesting PCNA acts as a scaffold for Cdt1.

Conclusions:

  • PCNA provides an immobile platform at DNA damage sites, facilitating the rapid and dynamic recruitment of Cdt1.
  • This PCNA-mediated recruitment mechanism ensures efficient Cdt1 accumulation at damaged DNA, preceding its subsequent degradation.
  • The findings highlight a critical interplay between cell cycle progression and DNA damage response, ensuring genomic stability.

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