Visualizing Binding of Single SMC Complexes to DNA Substrates Using Combinational Optical Tweezers and Fluorescence...

Area of Science:

• Molecular Biology
• Genomics
• Biophysics

Background:

• Structural Maintenance of Chromosomes (SMC) complexes play crucial roles in genome organization and maintenance.
• Characterizing SMC-DNA interactions is challenging due to complex dynamics and multiple binding sites.
• Fundamental questions persist regarding SMC substrate specificity, binding stability, and loading/unloading mechanisms.

Purpose of the Study:

• To detail methods for preparing eukaryotic SMC complexes (cohesin and Smc5/6) for single-molecule experiments.
• To enable visualization and characterization of individual SMC complexes binding to DNA substrates.
• To probe the influence of factors like ATP turnover and force on SMC-DNA interactions.

Main Methods:

• Utilizing correlative optical tweezers and fluorescence microscopy with microfluidics.
• Employing recombinant preparation of fluorophore-labeled SMC complexes and diverse DNA substrates.
• Leveraging the LUMICKS C-Trap system for high-resolution real-time analysis.

Main Results:

• Demonstrated a powerful toolkit for visualizing individual SMC complexes on DNA.
• Enabled probing of ATP turnover, force dependencies, and complex stoichiometry.
• Provided access to heterogeneous and transient SMC behaviors missed by ensemble assays.

Conclusions:

• Single-molecule techniques offer unprecedented resolution for studying SMC-DNA interactions.
• This approach facilitates a deeper understanding of genome organization and maintenance mechanisms.
• Custom data analysis scripts aid in automated detection and localization of DNA binding events.