The Sad1-UNC-84 homology domain in Mps3 interacts with Mps2 to connect the spindle pole body with the nuclear envelope

Area of Science:

• Cell Biology
• Molecular Biology
• Yeast Genetics

Background:

• The spindle pole body (SPB) in Saccharomyces cerevisiae is the primary site for microtubule nucleation.
• SPB assembly mechanisms, particularly the connection between its core and the half-bridge, remain incompletely understood.
• Integral membrane proteins like Mps2 anchor the SPB core to the nuclear envelope, while the half-bridge is involved in duplication and G1 microtubule nucleation.

Purpose of the Study:

• To elucidate the molecular interactions responsible for tethering the SPB half-bridge to the core SPB.
• To investigate the role of Mps3, a SUN protein family member, and its interaction with Mps2 in SPB assembly.

Main Methods:

• Cytological observation of SPB structures in wild-type and mutant yeast strains.
• Analysis of mutants affecting the Mps3 SUN domain and Mps2 C terminus.
• Biochemical investigation of the interaction between Mps3 and Mps2.

Main Results:

• Mps3, a budding yeast SUN protein, was identified as a component of the SPB half-bridge.
• Evidence suggests Mps3 interacts with the Mps2 C terminus, functionally linking the half-bridge to the core SPB.
• Mutations in Mps3 or Mps2 resulted in SPB duplication and karyogamy defects, correlating with observed aberrant half-bridge structures.

Conclusions:

• The interaction between the Mps3 SUN domain and Mps2 C terminus provides the first biochemical link connecting the SPB half-bridge to the core SPB.
• This interaction is essential for proper SPB duplication and karyogamy in budding yeast.
• Mps3 association with Mps2 reveals a novel function for Mps2 in SPB duplication.