Localization of the Kar3 Kinesin Heavy Chain-Related Protein Requires the Cik1 Interacting Protein

• Published in: The Journal of cell biology 1994-02, Vol.124 (4), p.507-519
• Main Authors: Page, Barbara D., Satterwhite, Lisa L., Rose, Mark D., Snyder, Michael
• Format: Article
• Language: English
• Subjects: Antibodies; Biological and medical sciences; Cell cycle; Cell physiology; Cells; Cellular biology; Cytoplasm - metabolism; Fluorescent Antibody Technique; Fundamental and applied biological sciences. Psychology; Fungal Proteins - genetics; Fungal Proteins - metabolism; Immunohistochemistry; Karyotyping; Microtubule Proteins; Microtubule-Associated Proteins; Microtubules; Microtubules - metabolism; Molecular and cellular biology; Motility and taxis; Perceptual localization; Phenotype; Phenotypes; Pheromones; Plasmids; Precipitin Tests; Proteins; Saccharomyces cerevisiae; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins; Somatic cells; Yeast; Yeasts
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.124.4.507

The Kar3 protein (Kar3p), a protein related to kinesin heavy chain, and the Cik1 protein (Cik1p) appear to participate in the same cellular processes in S. cerevisiae. Phenotypic analysis of mutants indicates that both CIK1 and KAR3 participate in spindle formation and karyogamy. In addition, the expression of both genes is induced by pheromone treatment. In vegetatively growing cells, both Cik1::β-gal and Kar3::β-gal fusions localize to the spindle pole body (SPB), and after pheromone treatment both fusion proteins localize to the spindle pole body and cytoplasmic microtubules. The dependence of Cik1p and Kar3p localization upon one another was investigated by indirect immunofluorescence of fusion proteins in pheromone-treated cells. The Cik1p::β-gal fusion does not localize to the SPB or microtubules in a kar3Δ strain, and the Kar3p::β-gal fusion protein does not localize to microtubule-associated structures in a cik1Δ strain. Thus, these proteins appear to be interdependent for localization to the SPB and microtubules. Analysis by both the two-hybrid system and coimmunoprecipitation experiments indicates that Cik1p and Kar3p interact, suggesting that they are part of the same protein complex. These data indicate that interaction between a putative kinesin heavy chain-related protein and another protein can determine the localization of motor activity and thereby affect the functional specificity of the motor complex.