Measuring PARP1 mobility at DNA damage sites by segmented fluorescence correlation spectroscopy

Area of Science:

• Cellular dynamics
• Molecular biology
• Biophysics

Background:

• Fluorescence correlation spectroscopy (FCS) is a powerful technique for measuring molecular dynamics in cells.
• Accurate FCS measurements can be challenging due to cellular complexity and photobleaching.
• Segmented FCS (sFCS) offers improved accuracy by analyzing data in short temporal segments.

Purpose of the Study:

• To apply segmented FCS (sFCS) to investigate the dynamics of poly(ADP-ribose) polymerase 1 (PARP1) in live cells.
• To measure PARP1 recruitment and mobility at DNA damage sites induced by laser micro-irradiation.
• To assess the impact of photobleaching on the measured dynamics.

Main Methods:

• Utilized a commercial confocal laser scanning microscope for segmented FCS measurements.
• Performed fast line scanning across the nucleoplasm of live cells.
• Applied laser micro-irradiation to induce localized DNA damage.
• Analyzed FCS data in distinct subcellular regions (damaged vs. undamaged).

Main Results:

• Demonstrated reduced mobility of PARP1 at DNA damage sites, indicating a binding fraction.
• Observed unaltered diffusion of PARP1 in undamaged nucleoplasm.
• Quantified PARP1 recruitment kinetics to DNA damage foci.
• Evaluated the influence of photobleaching on PARP1 dynamics measurements.

Conclusions:

• Segmented FCS enables accurate measurement of protein dynamics in specific subcellular locations.
• PARP1 exhibits reduced mobility at DNA damage sites, consistent with its role in DNA repair.
• sFCS is a valuable tool for studying protein dynamics in cellular responses to DNA damage.