Cryoelectron Microscopy Structure of a Yeast Centromeric Nucleosome at 2.7 Å Resolution

Area of Science:

• Cell Biology
• Molecular Biology
• Structural Biology

Background:

• Kinetochores are crucial for chromosome segregation during cell division.
• In budding yeast, kinetochores link centromeric nucleosomes (containing Cse4^CENP-A) to spindle microtubules.
• Yeast kinetochores offer a model for understanding more complex metazoan kinetochore structures.

Purpose of the Study:

• To develop a streamlined protocol for reconstituting yeast centromeric nucleosomes.
• To systematically explore cryo-grid preparation for high-resolution imaging.
• To determine the high-resolution structure of a reconstituted yeast centromeric nucleosome.

Main Methods:

• Reconstitution of yeast centromeric nucleosomes.
• Cryo-electron microscopy (cryo-EM) grid preparation and data collection.
• High-resolution cryo-EM data processing and structure determination.

Main Results:

• A streamlined protocol for yeast centromeric nucleosome reconstitution was established.
• High-resolution cryo-EM enabled detailed structural analysis.
• The structure revealed fewer DNA base pairs tightly associated with the histone octamer compared to canonical nucleosomes.

Conclusions:

• The determined centromeric nucleosome structure provides a foundation for studying kinetochore assembly.
• Weak DNA binding at the ends may facilitate recognition by other kinetochore proteins.
• This work facilitates further research into kinetochore biochemistry and chromatin structure.