Kinetochore function is controlled by a phospho-dependent coexpansion of inner and outer components

Area of Science:

• Cell Biology
• Molecular Biology
• Chromatin Biology

Background:

• Kinetochore assembly is hierarchical, starting with centromeric chromatin.
• Kinetochore protein recruitment often depends on microtubule attachment status.
• The orchestration of kinetochore protein assembly and disassembly remains poorly understood.

Purpose of the Study:

• To investigate the assembly and disassembly mechanisms of kinetochore proteins.
• To understand how kinetochore structure changes in response to microtubule attachment.
• To elucidate the role of mitotic kinases and phosphatases in kinetochore organization.

Main Methods:

• Utilized 3D structured illumination microscopy.
• Employed Xenopus laevis egg extracts for in vitro studies.
• Analyzed protein localization and structural changes under varying microtubule attachment conditions.

Main Results:

• In the absence of microtubule attachment, outer kinetochore proteins and CENP-C form large, fibrous structures over CENP-A-free chromatin.
• This expandable module includes proteins for lateral attachment and checkpoint signaling (Bub1, BubR1, Mad1, CENP-E).
• Assembly of this module is regulated by mitotic kinases (Aurora B, Mps1, Plx1) and inhibited by protein phosphatase 1.

Conclusions:

• Phospho-dependent coexpansion of CENP-C and outer kinetochore proteins facilitates checkpoint signaling and lateral attachment.
• Selective disassembly of this module is essential for transitioning to end-on microtubule attachment.
• This dynamic regulation ensures accurate chromosome segregation during mitosis.