Structural and dynamic mechanisms of CBF3-guided centromeric nucleosome formation

Area of Science:

• Molecular Biology
• Structural Biology
• Genetics

Background:

• Accurate chromosome segregation is crucial for cell division and relies on the centromere-kinetochore interface.
• In budding yeast, the CBF3 complex is essential for depositing CENP-A (a histone H3 variant) into centromeric nucleosomes.
• This deposition process is dependent on specific DNA sequences at the centromere.

Purpose of the Study:

• To determine the structural basis of centromeric nucleosome formation in budding yeast.
• To elucidate the mechanism by which the CBF3 complex recognizes and binds to centromeric DNA and nucleosomes.
• To provide insights into the conserved mechanisms of centromeric nucleosome assembly across species.

Main Methods:

• Cryo-electron microscopy (Cryo-EM) was used to determine high-resolution structures.
• Structural modeling and computational approaches were employed to analyze the complexes.
• Mutational studies were performed to validate key interactions.

Main Results:

• The structure of the centromeric nucleosome core containing CEN3 DNA and the CBF3core was determined.
• The CBF3core specifically recognizes a CCG motif within the nucleosomal DNA via its Gal4 domain, inducing DNA conformational changes.
• Dynamic interactions between the CBF3core, CENP-A, and histone H2B within the centromeric nucleosome were revealed.

Conclusions:

• This study provides unprecedented structural insights into the budding yeast centromeric nucleosome.
• The findings elucidate the mechanism of centromeric nucleosome assembly mediated by the CBF3 complex.
• The results have implications for understanding human centromeric nucleosome formation and chromosome segregation.