The Ndc80 complex uses a tripartite attachment point to couple microtubule depolymerization to chromosome movement

Area of Science:

• Cell Biology
• Molecular Biology
• Biophysics

Background:

• The Ndc80 complex is crucial for chromosome segregation during cell division.
• It links chromosomes to spindle microtubules via kinetochores.
• The N-terminal tail and calponin homology domain (CHD) of Hec1/Ndc80 are implicated in microtubule binding.

Purpose of the Study:

• To investigate the roles of the Hec1/Ndc80 tail and CHD in microtubule attachment and chromosome alignment.
• To determine how these domains cooperate to ensure stable kinetochore-microtubule interactions.

Main Methods:

• Point mutations were introduced into the Hec1/Ndc80 CHD in human cells.
• Chromosome alignment, kinetochore architecture, and spindle checkpoint protein recruitment were assessed.
• In vitro microtubule binding assays were performed.

Main Results:

• Mutations in the Hec1/Ndc80 CHD disrupted chromosome alignment and stable microtubule attachments.
• Kinetochore architecture and checkpoint signaling remained unaffected.
• Both the tail and CHD, through positively charged regions, are essential for stable microtubule binding, with the tail potentially enhancing CHD binding.

Conclusions:

• A tripartite interaction involving the Hec1/Ndc80 tail and two regions of the CHD mediates microtubule attachment.
• This complex interface is vital for coupling microtubule depolymerization to chromosome movement in vertebrates.