Structural basis for assembly of the CBF3 kinetochore complex.

Area of Science:

• Cell Biology
• Molecular Biology
• Structural Biology

Background:

• Centromeres are specialized chromosomal regions essential for kinetochore assembly and microtubule attachment in eukaryotes.
• Centromeres are characterized by CENP-A nucleosomes, a histone H3 variant.
• In budding yeast, the CBF3 complex recognizes specific DNA sequences to initiate centromere establishment.

Purpose of the Study:

• To determine the high-resolution structure of the core CBF3 complex.
• To elucidate the structural basis of CBF3 complex assembly.
• To understand the role of Ctf13 and Skp1 in CBF3 complex formation.

Main Methods:

• Single-particle cryo-electron microscopy (cryo-EM) at 3.6 Å resolution.
• Biochemical analysis of protein-protein interactions.

Main Results:

• A 3.6 Å cryo-EM reconstruction of the core CBF3 complex, including Cep3, Ctf13, and Skp1, was obtained.
• Ctf13 was structurally defined as an F-box protein belonging to the leucine-rich-repeat family.
• A novel F-box-mediated interaction between Ctf13 and Skp1 was identified as critical for initial CBF3 complex assembly.

Conclusions:

• The study provides the first structural insights into the core CBF3 complex.
• The findings reveal a novel mechanism for the assembly of the CBF3 complex mediated by Ctf13-Skp1 interaction.
• This structural understanding is fundamental for comprehending centromere establishment and kinetochore assembly in budding yeast.