title: Deletion of RNQ1 gene reveals novel functional relationship between divergently transcribed Bik1p/CLIP-170 and Sfi1p in spindle pole body separation.
abstract: Spindle pole body (SPB; the microtubule organizing center in yeast) duplication is essential to form a bipolar spindle. The duplicated SPBs must then separate and migrate to opposite sides of the nucleus. We identified a novel functional relationship in SPB separation between the microtubule stabilizing protein Bik1p/CLIP-170 and the SPB half-bridge protein Sfi1p. A genetic interaction between BIK1 and SFI1 was discovered in a synthetic lethal screen using a strain deficient in the prion protein gene RNQ1. RNQ1 deletion reduced expression from the divergently transcribed BIK1, allowing us to identify genetic interactors with bik1. The sfi1-1 bik1 synthetic lethality was suppressed by over-expression of CIK1, KAR1, and PPH21. Genetic analysis indicated that the sfi1-1 bik1 synthetic lethality was unlikely related to the function of Bik1p in the dynein pathway or to defects in spindle position. Furthermore, a sfi1-1 Deltakip2 mutant was viable, suggesting that the Bik1p pool at the cytoplasmic microtubule plus-ends may not be required in sfi1-1. Microscopic examination indicated the sfi1-1 mutant was delayed in SPB duplication, SPB separation, or spindle elongation and the sfi-1 Deltabik1 double mutant arrested with duplicated but unseparated SPBs. These results suggest that Bik1p has a previously uncharacterized function in the separation of duplicated SPBs.
authors.affiliation: Department of Cell Biology and Physiology, Washington University School of Medicine, 660 S Euclid Ave, Campus Box 8228, St Louis, MO, 63110, USA. htrue@cellbiology.wustl.edu
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Strawn
authors.forename: Heather L
authors.initials: HL
authors.lastname: True
mesh_terms: D000483:Alleles; D018797:Cell Cycle Proteins / Q000378:metabolism*; D004398:Dyneins / Q000235:genetics; D017353:Gene Deletion; D005804:Genes, Lethal; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D020409:Molecular Motor Proteins; D030781:Organisms, Genetically Modified; D011328:Prions / Q000235:genetics* / Q000378:metabolism; D012097:Repressor Proteins / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism*; D008941:Spindle Apparatus / Q000235:genetics* / Q000378:metabolism / Q000502:physiology; D014018:Tissue Distribution; D014158:Transcription, Genetic
chemical_list: C488173:Bik1 protein, S cerevisiae; D018797:Cell Cycle Proteins; C075341:KIP2 protein, S cerevisiae; D008869:Microtubule-Associated Proteins; D020409:Molecular Motor Proteins; D011328:Prions; C404807:RNQ1 protein, S cerevisiae; D012097:Repressor Proteins; C121820:SFI1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D004398:Dyneins