Constitutive dynein activity in She1 mutants reveals differences in microtubule attachment at the yeast spindle pole body.

Department of Molecular Biology and Genetics, Cornell University, Ithaca, NY 14853, USA.
Molecular biology of the cell (Impact Factor: 5.98). 04/2012; 23(12):2319-26. DOI: 10.1091/mbc.E12-03-0223
Source: PubMed

ABSTRACT The organization of microtubules is determined in most cells by a microtubule-organizing center, which nucleates microtubule assembly and anchors their minus ends. In Saccharomyces cerevisiae cells lacking She1, cytoplasmic microtubules detach from the spindle pole body at high rates. Increased rates of detachment depend on dynein activity, supporting previous evidence that She1 inhibits dynein. Detachment rates are higher in G1 than in metaphase cells, and we show that this is primarily due to differences in the strengths of microtubule attachment to the spindle pole body during these stages of the cell cycle. The minus ends of detached microtubules are stabilized by the presence of γ-tubulin and Spc72, a protein that tethers the γ-tubulin complex to the spindle pole body. A Spc72-Kar1 fusion protein suppresses detachment in G1 cells, indicating that the interaction between these two proteins is critical to microtubule anchoring. Overexpression of She1 inhibits the loading of dynactin components, but not dynein, onto microtubule plus ends. In addition, She1 binds directly to microtubules in vitro, so it may compete with dynactin for access to microtubules. Overall, these results indicate that inhibition of dynein activity by She1 is important to prevent excessive detachment of cytoplasmic microtubules, particularly in G1 cells.


Available from: Zane Bergman, Jun 11, 2015
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Accurate positioning of spindles is essential for asymmetric mitotic and meiotic cell divisions that are crucial for animal development and oocyte maturation, respectively. The predominant model for spindle positioning, termed "cortical pulling," involves attachment of the microtubule-based motor cytoplasmic dynein to the cortex, where it exerts a pulling force on microtubules that extend from the spindle poles to the cell cortex, thereby displacing the spindle. Recent studies have addressed important details of the cortical pulling mechanism and have revealed alternative mechanisms that may be used when microtubules do not extend from the spindle to the cortex.
    The Journal of Cell Biology 01/2013; 200(2):131-40. DOI:10.1083/jcb.201210007 · 9.69 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Timely spindle disassembly is essential for coordination of mitotic exit with cytokinesis. In the budding yeast Saccharomyces cerevisiae, the microtubule-associated protein She1 functions in one of at least three parallel pathways that promote spindle disassembly. She1 phosphorylation by the Aurora kinase Ipl1 facilitates a role for She1 in late anaphase, when She1 contributes to microtubule depolymerization and shrinkage of spindle halves. By examining the genetic interactions of known spindle disassembly genes, we identified three genes in the environmental stress-sensing HOG (High Osmolarity Glycerol response) pathway, SHO1, PBS2, and HOG1, and found they are necessary for proper localization of She1 to the anaphase spindle and for proper spindle disassembly. HOG pathway mutants exhibited spindle disassembly defects, as well as mislocalization of anillin-related proteins Boi1 and Boi2 from the bud neck. Moreover, Boi2, but not Boi1, plays a role in spindle disassembly that places Boi2 in a pathway with Sho1, Pbs2, and Hog1. Together, our data identify a process by which cells monitor events at the spindle and bud neck, and describe a novel role for the HOG pathway in mitotic signaling.
    Genetics 09/2014; 198(3). DOI:10.1534/genetics.114.163238 · 4.87 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: How do cells direct the microtubule motor protein dynein to move cellular components to the right place at the right time? Recent studies in budding yeast shed light on a new mechanism for directing dynein, involving the protein She1. She1 restricts where and when dynein moves the nucleus and mitotic spindle. Experiments with purified proteins show that She1 binds to microtubules and inhibits dynein by stalling the motor on its track. Here I describe what we have learned so far about She1, based on a combination of genetic, cell biology, and biophysical approaches. These findings set the stage for further interrogation of the She1 mechanism, and raise the question of whether similar mechanisms exist in other species.
    BioEssays 08/2013; 35(8). DOI:10.1002/bies.201300016 · 4.84 Impact Factor