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Conserved signalling functions for Mps1, Mad1 and Mad2 in the Cryptococcus neoformans spindle checkpoint
Koly Aktar1, Thomas Davies1, Ioanna Leontiou1
1Institute of Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom.
The spindle assembly checkpoint (SAC) in Cryptococcus neoformans is conserved, with Mps1 kinase and Mad1/Mad2 proteins ensuring accurate chromosome segregation during cell division.
Area of Science:
- Molecular Biology
- Cell Biology
- Mycology
Background:
- Cryptococcus neoformans is an opportunistic fungal pathogen causing human infections.
- Cell cycle control and ploidy in C. neoformans are altered by stress.
- The spindle assembly checkpoint (SAC) regulates the transition from metaphase to anaphase.
Purpose of the Study:
- To mechanistically analyze the spindle checkpoint in C. neoformans.
- To investigate the roles of Mps1 kinase and Mad1/Mad2 in SAC function.
- To understand how these components ensure faithful chromosome segregation.
Main Methods:
- Genetic analysis of mad1Δ and mad2Δ mutant strains.
- Fluorescent tagging of Chromosome 3 to assess sister-chromatid cohesion.
- Protein purification, mass spectrometry, and in vitro kinase assays.
Main Results:
- mad1Δ or mad2Δ mutants failed to respond to microtubule disruption and died.
- SAC components Mad1 and Mad2 are essential for maintaining sister-chromatid cohesion.
- Mps1 kinase overexpression arrested cells in mitosis, dependent on Mad1 and Mad2.
- Mps1 phosphorylates Mad1 at conserved C-terminal sites, critical for checkpoint signaling.
Conclusions:
- The spindle assembly checkpoint is conserved in Cryptococcus neoformans.
- CnMps1, Mad1, and Mad2 play crucial roles in the SAC.
- These proteins are vital for high-fidelity chromosome segregation in this fungal pathogen.
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