Differential contribution of Bud6p and Kar9p to microtubule capture and spindle orientation in S. cerevisiae.
In Saccharomyces cerevisiae, spindle orientation is controlled by a temporal and spatial program of microtubule (MT)-cortex interactions. This program requires Bud6p/Aip3p to direct the old pole to the bud and confine the new pole to the mother cell. Bud6p function has been linked to Kar9p, a protein guiding MTs along actin cables. Here, we show that Kar9p does not mediate Bud6p functions in spindle orientation. Based on live microscopy analysis, kar9Delta cells maintained Bud6p-dependent MT capture. Conversely, bud6Delta cells supported Kar9p-associated MT delivery to the bud. Moreover, additive phenotypes in bud6Delta kar9Delta or bud6Delta dyn1Delta mutants underscored the separate contributions of Bud6p, Kar9p, and dynein to spindle positioning. Finally, tub2C354S, a mutation decreasing MT dynamics, suppressed a kar9Delta mutation in a BUD6-dependent manner. Thus, Kar9p-independent capture at Bud6p sites can effect spindle orientation provided MT turnover is reduced. Together, these results demonstrate Bud6p function in MT capture at the cell cortex, independent of Kar9p-mediated MT delivery along actin cables.
Huisman
Stephen M
SM
Department of Genetics, University of Cambridge, Cambridge, CB2 3EH UK.
Bales
Olivia A M
OA
Bertrand
Marie
M
Smeets
Monique F M A
MF
Reed
Steven I
SI
Segal
Marisa
M
D000199:Actins / Q000737:chemistry / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D004398:Dyneins / Q000502:physiology; D005656:Fungal Proteins / Q000737:chemistry; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008840:Microfilament Proteins / Q000502:physiology*; D008856:Microscopy, Fluorescence; D008868:Microtubule Proteins / Q000737:chemistry; D008870:Microtubules / Q000648:ultrastructure*; D008954:Models, Biological; D009154:Mutation; D009687:Nuclear Proteins / Q000502:physiology*; D010641:Phenotype; D010957:Plasmids / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000502:physiology*; D008941:Spindle Apparatus; D013997:Time Factors
D000199:Actins; C107727:BUD6 protein, S cerevisiae; D005656:Fungal Proteins; C110443:KAR9 protein, S cerevisiae; D008840:Microfilament Proteins; D008868:Microtubule Proteins; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins; D004398:Dyneins