Interplay between septin organization, cell cycle and cell shape in yeast.
Septins are conserved filament-forming proteins that assemble into cortical cytoskeletal structures in animal and fungal cells. Although rapid progress has been made into the functions of septins, the mechanisms governing their localization and organization remain mysterious. In Saccharomyces cerevisiae, Cdc42p organizes the septin cytoskeleton into a ring in preparation for bud formation, following which septins remain as a collar at the mother-bud neck. We have dissected the phenotype of cdc42(V36T,K94E) cells that display an aberrant cell shape correlated with the development of ectopic septin caps and rings within the bud. The results suggest that a well-assembled septin cortex plays a novel role in directing growth to shape the nascent bud, and that a disorganized septin cortex directs improper growth generating an aberrant neck. Conversely, we found that the elongated bud shape arising as a result of the morphogenesis checkpoint cell cycle delay that accompanies septin perturbation can feed back to exacerbate minor defects in septin organization, by maintaining a bud-tip-localized septin assembly activity that competes with the neck-localized septin cortex. Using this exacerbation as a tool, we uncovered septin organization defects in many mutants not previously known to display such defects, expanding the cast of characters involved in proper assembly of the septin cortex to include CLN1, CLN2, BNI1, BNI4, BUD3, BUD4 and BUD5.
Gladfelter
Amy S
AS
Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
Kozubowski
Lukasz
L
Zyla
Trevin R
TR
Lew
Daniel J
DJ
D002453:Cell Cycle / Q000502:physiology*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division / Q000502:physiology; D048430:Cell Shape / Q000502:physiology*; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D003599:Cytoskeleton / Q000235:genetics / Q000378:metabolism; D016195:G2 Phase / Q000502:physiology; D018816:Genes, cdc / Q000502:physiology; D008565:Membrane Proteins / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D015388:Organelles / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism
D018797:Cell Cycle Proteins; D003598:Cytoskeletal Proteins; D008565:Membrane Proteins; D029701:Saccharomyces cerevisiae Proteins; C099685:SWE1 protein, S cerevisiae; D011505:Protein-Tyrosine Kinases; D020846:cdc42 GTP-Binding Protein, Saccharomyces cerevisiae