title: Determinants of S. cerevisiae dynein localization and activation: implications for the mechanism of spindle positioning.
abstract: BACKGROUND
  During anaphase in budding yeast, dynein inserts the mitotic spindle across the neck between mother and daughter cells. The mechanism of dynein-dependent spindle positioning is thought to involve recruitment of dynein to the cell cortex followed by capture of astral microtubules (aMTs).
  
  
  RESULTS
  We report the native-level localization of the dynein heavy chain and characterize the effects of mutations in dynein regulators on its intracellular distribution. Budding yeast dynein displays discontinuous localization along aMTs, with enrichment at the spindle pole body and aMT plus ends. Loss of Bik1p (CLIP-170), the cargo binding domain of Bik1p, or Pac1p (LIS1) resulted in diminished targeting of dynein to aMTs. By contrast, loss of dynactin or a mutation in the second P loop domain of dynein resulted in an accumulation of dynein on the plus ends of aMTs. Unexpectedly, loss of Num1p, a proposed dynein cortical anchor, also resulted in selective accumulation of dynein on the plus ends of anaphase aMTs.
  
  
  CONCLUSIONS
  We propose that, rather than first being recruited to the cell cortex, dynein is delivered to the cortex on the plus ends of polymerizing aMTs. Dynein may then undergo Num1p-dependent activation and transfer to the region of cortical contact. Based on the similar effects of loss of Num1p and loss of dynactin on dynein localization, we suggest that Num1p might also enhance dynein motor activity or processivity, perhaps by clustering dynein motors.
authors.affiliation: Department of Pediatric Oncology, The Dana Farber Cancer Institute, The Children's Hospital, Harvard Medical School, 44 Binney Street, Boston, MA 02115, USA.
authors.forename: Brina
authors.initials: B
authors.lastname: Sheeman
authors.forename: Pedro
authors.initials: P
authors.lastname: Carvalho
authors.forename: Isabelle
authors.initials: I
authors.lastname: Sagot
authors.forename: John
authors.initials: J
authors.lastname: Geiser
authors.forename: David
authors.initials: D
authors.lastname: Kho
authors.forename: M Andrew
authors.initials: MA
authors.lastname: Hoyt
authors.forename: David
authors.initials: D
authors.lastname: Pellman
mesh_terms: D004398:Dyneins / Q000378:metabolism*; D004722:Endoribonucleases; D005656:Fungal Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D008941:Spindle Apparatus / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: D005656:Fungal Proteins; D029701:Saccharomyces cerevisiae Proteins; D004722:Endoribonucleases; C499539:PAC1 protein, S cerevisiae; D004398:Dyneins