Control of mitotic spindle position by the Saccharomyces cerevisiae formin Bni1p

J Cell Biol. 1999 Mar 8;144(5):947-61. doi: 10.1083/jcb.144.5.947.

Abstract

Alignment of the mitotic spindle with the axis of cell division is an essential process in Saccharomyces cerevisiae that is mediated by interactions between cytoplasmic microtubules and the cell cortex. We found that a cortical protein, the yeast formin Bni1p, was required for spindle orientation. Two striking abnormalities were observed in bni1Delta cells. First, the initial movement of the spindle pole body (SPB) toward the emerging bud was defective. This phenotype is similar to that previously observed in cells lacking the kinesin Kip3p and, in fact, BNI1 and KIP3 were found to be in the same genetic pathway. Second, abnormal pulling interactions between microtubules and the cortex appeared to cause preanaphase spindles in bni1Delta cells to transit back and forth between the mother and the bud. We therefore propose that Bni1p may localize or alter the function of cortical microtubule-binding sites in the bud. Additionally, we present evidence that other bipolar bud site determinants together with cortical actin are also required for spindle orientation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Actins / metabolism
  • Base Sequence
  • Binding Sites
  • DNA Primers
  • Fungal Proteins / metabolism
  • Fungal Proteins / physiology*
  • Microfilament Proteins / metabolism
  • Microfilament Proteins / physiology
  • Microscopy, Fluorescence
  • Microtubules
  • Molecular Sequence Data
  • Saccharomyces cerevisiae / cytology*
  • Saccharomyces cerevisiae / genetics
  • Saccharomyces cerevisiae / physiology
  • Saccharomyces cerevisiae Proteins*
  • Spindle Apparatus / physiology*

Substances

  • Actins
  • BUD6 protein, S cerevisiae
  • Bni1 protein, S cerevisiae
  • DNA Primers
  • Fungal Proteins
  • Microfilament Proteins
  • Saccharomyces cerevisiae Proteins