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Gene Review

KAR3  -  Kar3p

Saccharomyces cerevisiae S288c

Synonyms: Kinesin-like protein KAR3, Nuclear fusion protein, P9659.16, YPR141C
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Disease relevance of KAR3

  • Heat-stress, nitrogen-starvation and cultivation on ethanol failed to affect the growth of osr11 and kar3 mutants, pointing to a possible specific involvement of KAR3 in the osmotic-stress response [1].

High impact information on KAR3

  • The yeast kinesin motor protein Kar3 forms a heterodimer with a nonmotor protein Vik1 [2].
  • Deletion of kinesin-related KAR3 partially suppressed the phenotypes associated with loss of Cin8p/Kip1p function [3].
  • The phenotypes of kar3 mutants suggest that the protein mediates microtubule sliding during nuclear fusion and possibly mitosis [4].
  • Here we report that a mutation in the motor domain of the microtubule motor proteins Kar3 and Ncd uncouples nucleotide- and microtubule-binding by the proteins, preventing activation of the motor ATPase by microtubules [5].
  • The MT plus end-binding proteins Kar3p, a class 14 COOH-terminal kinesin, and Bik1p, the CLIP-170 orthologue, localize to plus ends in the shmoo tip and initiate MT interactions and depolymerization after cell wall breakdown [6].

Biological context of KAR3

  • Deletion of KAR3 leads to a dramatic increase in cytoplasmic microtubules, a phenotype which is most pronounced from START through the onset of anaphase but less so during late anaphase in synchronized cultures [7].
  • Increased ploidy and KAR3 and SIR3 disruption alter the dynamics of meiotic chromosomes and telomeres [8].
  • Six of the seven were unaffected for the essential karyogamy and meiosis properties of KAR3 and the seventh was dominant for the suppressing trait [9].
  • We have immunolocalized HA-tagged Kar3p to the spindle pole body region, and fittingly, Kar3p was not detected by late anaphase [7].
  • Cik1p and Vik1p are kinesin-associated proteins known to modulate the function of Kar3p in the microtubule-dependent processes of karyogamy and mitosis [10].

Anatomical context of KAR3


Associations of KAR3 with chemical compounds

  • This motor contains an NH2-terminal glutathione S-transferase (GST) tag followed by the Kar3 sequence that is predicted to form an extended alpha-helical coiled-coil [13].
  • Sucrose gradient velocity centrifugation and gel filtration experiments were used to determine the size of the Kar3-Cik1 complex from both mating pheromone-treated cells and vegetatively growing cells [14].

Physical interactions of KAR3


Regulatory relationships of KAR3

  • Loss of function of Saccharomyces cerevisiae kinesin-related CIN8 and KIP1 is suppressed by KAR3 motor domain mutations [9].
  • Consistent with its mutant phenotype, we found that the kar4 mutation resulted in failure to induce KAR3 and CIK1 mRNA during mating [17].
  • Comparison of the expression of meiosis-specific Ndj1p-HA and Zip1p in haploid control and kar3Delta time courses revealed that fewer cells enter the meiotic cycle in absence of Kar3p [8].
  • The observation that deletion of KIP2 could also suppress the inviability of dyn1Delta kar3Delta cells suggests that kinesin-related Kar3p also contributes to spindle positioning [18].
  • Thus, structural changes in Kar3 upon dimerization with Cik1 alter the motor velocity and likely regulate Kar3 activity in vivo [19].

Other interactions of KAR3

  • Localization of the Kar3 kinesin heavy chain-related protein requires the Cik1 interacting protein [20].
  • A preanaphase spindle collapse phenotype of cin8 kip1 mutants, previously shown to involve Kar3p, is markedly delayed when microtubule depolymerization is inhibited by the tub2-150 mutation [7].
  • Our findings suggest that despite an antagonistic relationship between Cin8p/Kip1p and Kar3p, aspects of their mitotic roles may be similar [9].
  • Addition of the microtubule polymerization inhibitors nocodazol or benomyl to the medium or deletion of the nonessential alpha-tubulin TUB3 gene can mostly correct the abnormal microtubule arrays and other growth defects of kar3 mutants, suggesting that these phenotypes result from excessive microtubule polymerization [7].
  • Overproduction of Ste12p suppressed the kar4 defect in KAR3 induction and nuclear fusion [17].

Analytical, diagnostic and therapeutic context of KAR3


  1. A Saccharomyces cerevisiae mutant defective in the kinesin-like protein Kar3 is sensitive to NaCl-stress. Schoch, C.L., Br-uning, A.R., Entian, K.D., Pretorius, G.H., Prior, B.A. Curr. Genet. (1997) [Pubmed]
  2. Kinesin kar3 and vik1 go head to head. Woehlke, G., Schliwa, M. Cell (2007) [Pubmed]
  3. Kinesin-related proteins required for structural integrity of the mitotic spindle. Saunders, W.S., Hoyt, M.A. Cell (1992) [Pubmed]
  4. KAR3, a kinesin-related gene required for yeast nuclear fusion. Meluh, P.B., Rose, M.D. Cell (1990) [Pubmed]
  5. Decoupling of nucleotide- and microtubule-binding sites in a kinesin mutant. Song, H., Endow, S.A. Nature (1998) [Pubmed]
  6. Nuclear congression is driven by cytoplasmic microtubule plus end interactions in S. cerevisiae. Molk, J.N., Salmon, E.D., Bloom, K. J. Cell Biol. (2006) [Pubmed]
  7. The Saccharomyces cerevisiae kinesin-related motor Kar3p acts at preanaphase spindle poles to limit the number and length of cytoplasmic microtubules. Saunders, W., Hornack, D., Lengyel, V., Deng, C. J. Cell Biol. (1997) [Pubmed]
  8. Increased ploidy and KAR3 and SIR3 disruption alter the dynamics of meiotic chromosomes and telomeres. Trelles-Sticken, E., Loidl, J., Scherthan, H. J. Cell. Sci. (2003) [Pubmed]
  9. Loss of function of Saccharomyces cerevisiae kinesin-related CIN8 and KIP1 is suppressed by KAR3 motor domain mutations. Hoyt, M.A., He, L., Totis, L., Saunders, W.S. Genetics (1993) [Pubmed]
  10. The Kar3-interacting protein Cik1p plays a critical role in passage through meiosis I in Saccharomyces cerevisiae. Shanks, R.M., Kamieniecki, R.J., Dawson, D.S. Genetics (2001) [Pubmed]
  11. Nuclear fusion-defective phenocopies in Chlamydomonas reinhardtii: mating-type functions for meiosis can act through the cytoplasm. Dutcher, S.K. Proc. Natl. Acad. Sci. U.S.A. (1988) [Pubmed]
  12. Electron microscopy of ascus formation in the yeast debaryomyces hansenii. Kreger van Rij, N.J., Veenhuis, M. J. Gen. Microbiol. (1975) [Pubmed]
  13. Mechanistic analysis of the Saccharomyces cerevisiae kinesin Kar3. Mackey, A.T., Sproul, L.R., Sontag, C.A., Satterwhite, L.L., Correia, J.J., Gilbert, S.P. J. Biol. Chem. (2004) [Pubmed]
  14. The Kar3p kinesin-related protein forms a novel heterodimeric structure with its associated protein Cik1p. Barrett, J.G., Manning, B.D., Snyder, M. Mol. Biol. Cell (2000) [Pubmed]
  15. Role of transcription factor Kar4 in regulating downstream events in the Saccharomyces cerevisiae pheromone response pathway. Lahav, R., Gammie, A., Tavazoie, S., Rose, M.D. Mol. Cell. Biol. (2007) [Pubmed]
  16. The minus end-directed motor Kar3 is required for coupling dynamic microtubule plus ends to the cortical shmoo tip in budding yeast. Maddox, P.S., Stemple, J.K., Satterwhite, L., Salmon, E.D., Bloom, K. Curr. Biol. (2003) [Pubmed]
  17. Kar4p, a karyogamy-specific component of the yeast pheromone response pathway. Kurihara, L.J., Stewart, B.G., Gammie, A.E., Rose, M.D. Mol. Cell. Biol. (1996) [Pubmed]
  18. Mitotic spindle positioning in Saccharomyces cerevisiae is accomplished by antagonistically acting microtubule motor proteins. Cottingham, F.R., Hoyt, M.A. J. Cell Biol. (1997) [Pubmed]
  19. Kar3 interaction with Cik1 alters motor structure and function. Chu, H.M., Yun, M., Anderson, D.E., Sage, H., Park, H.W., Endow, S.A. EMBO J. (2005) [Pubmed]
  20. Localization of the Kar3 kinesin heavy chain-related protein requires the Cik1 interacting protein. Page, B.D., Satterwhite, L.L., Rose, M.D., Snyder, M. J. Cell Biol. (1994) [Pubmed]
  21. Yeast Bim1p promotes the G1-specific dynamics of microtubules. Tirnauer, J.S., O'Toole, E., Berrueta, L., Bierer, B.E., Pellman, D. J. Cell Biol. (1999) [Pubmed]
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