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Seminar: New aspects of cell polarity control in fission yeast, Professor Kenneth Sawin, School of Biological Sciences, University of Edinburgh
Abstract: Fission yeast are highly polarised, cylindrical cells that grow by new membrane deposition and cell wall synthesis exclusively at cell tips. I will describe two stories about our recent work on cell polarity regulation in this model eukaryote. One story concerns our discovery that Sty1, a MAP kinase in the conserved stress-activated protein kinase pathway, is a key regulator of the cell polarity module controlled by the Rho-family small GTPase Cdc42.
As part of this we developed a novel system that allows us to reversibly switch on Sty1 kinase actvity in the complete absence of external stress. The other story concerns internal cues/landmarks that determine which tips of newly-born daughter cells will be chosen as growth sites after septation. We have found that three different internal cues collaborate and compete to regulate patterns of polarised growth in daughter cells. One of these cues is a novel “growth-memory” cue, which remembers prior growth history during times of no growth—essentially an epigenetic phenomenon, in the older sense of the term “epigenetic”. We are beginning to address the molecular nature of this growth-memory cue.
Biography: Ken Sawin studied physics and philosophy as an undergraduate but changed to cell biology after his degree. He did his PhD with Tim Mitchison at the University of California, San Francisco, where he developed assays for mitotic spindle assembly in vitro and discovered the mitotic spindle kinesin motor protein Eg5.
He did postdoctoral work with Paul Nurse at the Imperial Cancer Research Fund, where he began to study the role of microtubules in regulating cell polarity in fission yeast. Since 2000 he has been a group leader at the Wellcome Trust Centre for Cell Biology at the University of Edinburgh, where he is currently Professor of Cell Biology. Current work in the laboratory is divided between studying molecular mechanisms of microtubule nucleation and regulation of cell polarity in fission yeast, using a combination of microscopy, genetics, biochemistry.