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Mutations which block the binding of calmodulin to Spc110p cause multiple mitotic defects
D A Stirling1, T F Rayner, A R Prescott
1Department of Biochemistry, The University, Dundee, UK.
Journal of Cell Science
|June 1, 1996
Summary
Mutations in SPC110 disrupt calmodulin binding, leading to cell cycle defects. Yeast cells with altered Spc110p function fail to segregate DNA, resulting in cell death and abnormal spindle formation.
Area of Science:
- Cell Biology
- Molecular Genetics
Background:
- The spindle pole body (SPB) is crucial for yeast cell division.
- SPC110 encodes a key SPB component, Spc110p, which interacts with calmodulin (CaM).
Purpose of the Study:
- To investigate the functional consequences of impaired CaM binding to Spc110p.
- To characterize temperature-sensitive mutations affecting CaM binding in SPC110.
Main Methods:
- Generated three temperature-sensitive SPC110 alleles with mutations in the CaM binding site.
- Analyzed cell cycle progression and SPB dynamics at restrictive temperatures.
- Assessed CaM binding in vitro and suppression by CMD1 gene dosage.
Main Results:
- Mutant Spc110p proteins showed reduced or absent CaM binding, confirmed by CMD1 gene dosage suppression.
- Cells with defective CaM binding replicated DNA but lost viability.
- spc110-124 exhibited abnormal metaphase with failed spindle formation.
- spc110-111 displayed broken spindles with detached SPBs.
Conclusions:
- Effective CaM binding to Spc110p is essential for proper SPB duplication and function.
- Disruption of CaM-Spc110p interaction leads to catastrophic cell division failures, including abnormal metaphase and broken spindles.
- These findings highlight the critical role of CaM in regulating yeast SPB dynamics and cell cycle progression.
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