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Published on: April 20, 2017
Mutation of Ser172 in yeast β tubulin induces defects in microtubule dynamics and cell division
Fabrice Caudron1, Eric Denarier, Jenny-Constanza Thibout-Quintana
1Institute of Biochemistry, ETH Zurich, Zurich, Switzerland.
Abstract:
Ser172 of β tubulin is an important residue that is mutated in a human brain disease and phosphorylated by the cyclin-dependent kinase Cdk1 in mammalian cells. To examine the role of this residue, we used the yeast S. cerevisiae as a model and produced two different mutations (S172A and S172E) of the conserved Ser172 in the yeast β tubulin Tub2p. The two mutants showed impaired cell growth on benomyl-containing medium and at cold temperatures, altered microtubule (MT) dynamics, and altered nucleus positioning and segregation. When cytoplasmic MT effectors Dyn1p or Kar9p were deleted in S172A and S172E mutants, cells were viable but presented increased ploidy. Furthermore, the two β tubulin mutations exhibited synthetic lethal interactions with Bik1p, Bim1p or Kar3p, which are effectors of cytoplasmic and spindle MTs. In the absence of Mad2p-dependent spindle checkpoint, both mutations are deleterious. These findings show the importance of Ser172 for the correct function of both cytoplasmic and spindle MTs and for normal cell division.
Insights
Mutations at Serine 172 in beta tubulin disrupt microtubule (MT) functions and cell division. This residue is crucial for maintaining MT dynamics and proper cell cycle progression in yeast models.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Serine 172 (Ser172) of beta-tubulin is implicated in human brain disease and phosphorylated by cyclin-dependent kinase 1 (Cdk1).
- Understanding the function of this conserved residue is crucial for comprehending microtubule (MT) roles in cellular processes.
Purpose of the Study:
- To investigate the functional significance of the conserved Ser172 residue in yeast beta-tubulin (Tub2p).
- To elucidate the role of Ser172 in microtubule dynamics, cell growth, and cell division using genetic manipulation.
Main Methods:
- Site-directed mutagenesis was used to create Ser172 to Alanine (S172A) and Ser172 to Glutamic acid (S172E) mutations in yeast beta-tubulin (Tub2p).
- Phenotypic analysis of mutants included cell growth assays (benomyl, cold sensitivity), assessment of microtubule dynamics, nucleus positioning, and ploidy.
- Genetic interactions were examined by deleting genes encoding MT effectors (Dyn1p, Kar9p, Bik1p, Bim1p, Kar3p) and the spindle checkpoint protein Mad2p.
Main Results:
- S172A and S172E beta-tubulin mutants exhibited impaired cell growth, altered MT dynamics, and defects in nucleus positioning and segregation.
- Deletion of cytoplasmic MT effectors in these mutants led to viable cells with increased ploidy.
- Synthetic lethal interactions were observed with effectors of cytoplasmic and spindle MTs, and mutations were deleterious in the absence of the spindle checkpoint.
Conclusions:
- Conserved Ser172 in beta-tubulin is essential for the proper function of both cytoplasmic and spindle microtubules.
- This residue plays a critical role in maintaining microtubule dynamics, ensuring accurate chromosome segregation, and facilitating normal cell division.
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