Dissecting chromatin interactions in living cells from protein mobility maps

Area of Science:

• Molecular Biology
• Cell Biology
• Genetics

Background:

• Eukaryotic genomes are organized into chromatin, a dynamic nucleoprotein complex.
• Post-translational modifications of DNA and proteins regulate gene expression.
• Chromatin-interacting proteins control the spatio-temporal coordination of these modifications.

Purpose of the Study:

• To measure chromatin binding of proteins in living cells using spatially resolved analysis of protein mobility.
• To combine different fluorescence microscopy techniques for a comprehensive understanding of chromatin dynamics.
• To illustrate the application of these techniques for analyzing heterochromatin protein 1 mobility.

Main Methods:

• Fluorescence microscopy-based approaches for protein mobility analysis.
• Fluorescence bleaching techniques to characterize immobile particles (second/minute timescale).
• Correlation analysis to characterize transient binding events (millisecond timescale).

Main Results:

• Advanced fluorescence microscopy provides data on diffusion coefficients, binding kinetics, and cellular concentrations.
• Combining bleaching and correlation methods allows dissection of diffusive translocations, binding events, and mobility constraints.
• Synergistic effects of different approaches yield protein mobility and interaction maps in the nucleus.

Conclusions:

• A combination of fluorescence bleaching and correlation analysis is essential for a comprehensive understanding of chromatin-interacting protein dynamics.
• These methods enable detailed mapping of protein mobility and interactions within the nucleus.
• The study provides a framework for analyzing chromatin-associated proteins, exemplified by heterochromatin protein 1.