Mutation of Ser172 in Yeast β Tubulin Induces Defects in Microtubule Dynamics and Cell Division

Fabrice Caudron,Anne Fourest-Lieuvin,Eric Denarier,Jacques Brocard,Annie Andrieux,Jenny-Constanza Thibout-Quintana

doi:10.1371/journal.pone.0013553

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.

Highlights

In mammalian cells, as in the budding yeast Saccharomyces cerevisiae, microtubules (MTs) form a dynamic network essential for many cellular processes, including cell polarity, organelle positioning and cell division
Yeast as a cell model for the study of Ser172 in b tubulin Ser172 of b tubulin is an important residue that is mutated in a human brain disease and phosphorylated by the cyclin-dependent kinase Cdk1 in mammalian cells
We showed previously in mammalian cells that b tubulin Ser172 is phosphorylated during mitosis by the cyclin-dependent kinase Cdk1 [21]

Summary

Introduction

As in the budding yeast Saccharomyces cerevisiae, microtubules (MTs) form a dynamic network essential for many cellular processes, including cell polarity, organelle positioning and cell division. In mammalian cells, during prophase and metaphase the nuclear envelope breaks down while MTs contact kinetochores to form the spindle. Contacts between the cMTs and the cell cortex are primordial for a correct positioning of the yeast mitotic nucleus at the neck between mother and bud cells. This positioning of the nucleus will eventually result in an accurate segregation of the genetic material between the two cells [2,3,4]. Astral MTs of the mitotic spindle are required to position the metaphase plate where the cleavage furrow will take place [5,6,7]

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