Regulation of Cell Polarity by Microtubules in Fission Yeast

Abstract

To investigate the role of microtubules in regulating cell polarity in Schizosaccharomyces pombe, we have developed a system in which normally cylindrical fission yeast synchronously form branched cells at high frequency upon treatment with the microtubule-depolymerizing drug thiabendazole (TBZ). Branching depends on both elevated temperature and cell cycle state and occurs at high frequency only when TBZ is added to cells that have not yet passed through New-End Take-Off (NETO), the normal transition from monopolar to bipolar growth. This suggests that microtubules may be of greatest physiological importance for the maintenance of cell shape at specific points in the cell cycle. The localization of three different proteins normally found at cell ends—cortical F-actin, tea1, and an ral3 (scd2)–green fluorescent protein (GFP) fusion—is disrupted by TBZ treatment. However, these proteins can eventually return to cell ends in the absence of microtubules, indicating that although their localization to ends normally depends on microtubules, they may recover by alternative mechanisms. In addition, TBZ induces a shift in ral3–GFP distribution from cell ends to the cell middle, suggesting that a protein complex containing ral3 may be part of the cue that specifies the position of branch formation.

Two Related Kinesins,klp5+andklp6+, Foster Microtubule Disassembly and Are Required for Meiosis in Fission Yeast

“…This result is consistent with the hypothesis that the phenotype arises as a result of hyperstabilized microtubules, because higher temperatures generally favor microtubule assembly. A similar temperature dependence has been reported for cell morphology defects observed in cells treated with TBZ (Sawin and Nurse, 1998). Because the cell cycle mutants used here to produce long cells are all temperature sensitive, it is not possible to distinguish clearly between the effects of temperature and cell length.…”

“…Previous work has demonstrated that shortening microtubule length, either by mutations in tubulin or tubulin-Cofactor genes (Umesono et al, 1983;Grishchuk and McIntosh, 1999;Radcliffe et al, 1999), by the addition of TBZ (Sawin and Nurse, 1998), or by deletion of microtubule-associated proteins (mal3 ϩ , Beinhauer et al, 1997;tea2 ϩ , Browning et al, 2000;tip1 ϩ , Brunner and Nurse, 2000; dis1 ϩ and mtc1 ϩ , Nakaseko et al, 2001) leads to the formation of T-shaped cells. Results presented here suggest that an increase in microtubule length can cause bending at the growing ends of the cells, resulting in C-or J-shaped cells.…”

Overproduction of elongation factor 1α, an essential translational component, causes aberrant cell morphology by affecting the control of growth polarity in fission yeast

“…Tea1 also functions in the microtubule cytoskeleton and is important for generating global spatial order (Mata & Nurse 1997). Recently, Sawin & Nurse developed a system in which the fission yeast cells synchronously form branched cells at high frequency following treatment with TBZ (Sawin & Nurse 1998). They also showed that branching depended on both elevated temperature and cell-cycle stage.…”

Roles of a Fimbrin and an α-Actinin-like Protein in Fission Yeast Cell Polarization and Cytokinesis

“…Immunofluorescence of 3HA-tagged cells was performed as described previously (Bähler and Pringle, 1998), using the monoclonal HA11 primary antibody (Berkeley Antibody, Richmond, CA) and fluorescein isothiocyanate (FITC)-tagged goat anti-mouse-IgG secondary antibody (Jackson ImmunoResearch, Laboratories, West Grove, PA). Staining of F-actin with rhodamine-phalloidin (Molecular Probes, Eugene, OR) was performed using the method of Sawin and Nurse (1998) Figure 1. Identification of the fim1 start codon (see text for details).…”