Using atomic force microscopy to study nucleosome remodeling on individual nucleosomal arrays in situ

Area of Science:

• Molecular Biology
• Genetics
• Biophysics

Background:

• Genomic processes in eukaryotes necessitate nucleosome structure alterations.
• ATP-dependent nucleosome remodeling complexes are key regulators of these changes.
• Understanding their mechanisms is crucial for comprehending gene regulation and DNA dynamics.

Purpose of the Study:

• To investigate the in situ action of the human Swi-Snf remodeling complex on nucleosomal arrays.
• To visualize and characterize structural changes induced by nucleosome remodeling at the single-molecule level.

Main Methods:

• Utilized atomic force microscopy (AFM) in situ technique for high-resolution imaging.
• Compared individual nucleosomal arrays before and after human Swi-Snf activation.
• Analyzed single-copy mouse mammary tumor virus promoter nucleosomal arrays.

Main Results:

• Observed diverse structural changes upon nucleosome remodeling by human Swi-Snf.
• Detected larger-scale alterations than previously reported.
• Identified a preference for removing a full turn (80 basepairs) of nucleosomal DNA.

Conclusions:

• The human Swi-Snf complex induces significant structural rearrangements in nucleosomes.
• The observed DNA removal suggests a potential interaction with the histone surface.
• This finding offers new insights into the mechanism of ATP-dependent chromatin remodeling.