Schizosaccharomyces pombe Ras1 effector, Scd1, interacts with Klp5 and Klp6 kinesins to mediate cytokinesis

Genetics. 2003 Oct;165(2):477-88. doi: 10.1093/genetics/165.2.477.


Fission yeast Scd1 is an exchange factor for Cdc42 and an effector of Ras1. In a screen for scd1 interacting genes, we isolated klp5 and klp6, which encode presumptive kinesins. Klp5 and Klp6 form a complex to control the same processes, which so far include microtubule dynamics and chromosome segregation. We showed that klp5 or klp6 inactivation in combination with the scd1 deletion (scd1delta) created a synthetic temperature-dependent growth defect. Further genetic analysis demonstrated that Klp5 and Klp6 interacted specifically with the Ras1-Scd1 pathway, but not with the Ras1-Byr2 pathway. In addition, Klp5 and Klp6 can stably associate with Scd1 and Cdc42. A deletion in the Scd1 C terminus, which contains the PB1 domain, prevented Scd1 binding to Klp5/6 and caused a growth defect in Klp5/6 mutant cells that is indistinguishable from that induced by scd1delta. Analysis of the double-mutant phenotype indicated that at the nonpermissive temperature, cells failed to undergo cytokinesis efficiently. These cells contained abnormal contractile rings in which F-actin and Mid1, a key regulator of F-actin ring formation and positioning, are mispositioned and fragmented. These data suggest that Klp5/6 cooperate with the Ras1-Scd1 pathway to influence proper formation of the contractile ring for cytokinesis.

Publication types

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

MeSH terms

  • Actins / metabolism
  • Cell Cycle Proteins / metabolism*
  • Cell Division / physiology
  • GTP-Binding Proteins / metabolism
  • Guanine Nucleotide Exchange Factors*
  • Kinesins / genetics
  • Kinesins / metabolism*
  • MAP Kinase Kinase Kinases / metabolism
  • Microtubule-Associated Proteins / genetics
  • Microtubule-Associated Proteins / metabolism*
  • Mutation
  • Proto-Oncogene Proteins / metabolism*
  • Schizosaccharomyces / cytology
  • Schizosaccharomyces / metabolism*
  • Schizosaccharomyces pombe Proteins / genetics
  • Schizosaccharomyces pombe Proteins / metabolism*
  • ras Proteins*


  • Actins
  • Cell Cycle Proteins
  • Guanine Nucleotide Exchange Factors
  • Microtubule-Associated Proteins
  • Proto-Oncogene Proteins
  • Schizosaccharomyces pombe Proteins
  • scd1 protein, S pombe
  • BYR2 protein, S pombe
  • MAP Kinase Kinase Kinases
  • GTP-Binding Proteins
  • Klp5 protein, S pombe
  • Klp6 protein, S pombe
  • Kinesins
  • Ras1 protein, S pombe
  • ras Proteins