Regulation of the Motor Function of S. cerevisiae Kinesin-5 proteins

Abstract

The conserved Kinesin-5 motor proteins play essential roles in the mitotic spindle morphogenesis. Although the Kinesin-5 functions were demonstrated in various stages of mitosis, the mechanisms that regulate their intracellular activity and motile properties have not yet been elucidated. In the present study, we examined anaphase B functions [1-3], regulation of intracellular activity and motile properties of two S. cerevisiae Kinesin-5 homologues, Cin8 and Kip1. We show that Cin8 and Kip1 exhibit different localization patterns to the mitotic spindle during anaphase B. We also show that Cin8 is differentially phosphorylated during anaphase at the Cdc2-kinase phosphorylation sites, located in its motor domain. To study the regulation of the motile properties of Cin8 and Kip1, we examined their microtubule binding and motility directly from cell-extracts, by the single-molecule assay. We found that Cin8 is faster compared to Kip1 and that Cin8's motile properties are dependent on a unique 99 amino-acid insert in its catalytic domain. Finally, we show that phosphorylation of Cin8 regulates its localization to the anaphase spindles and affects spindle elongation rates and morphology. Based on these findings, we propose a model for regulation of Kinesin-5 function during mitotic spindle morphogenesis.1. N. Movshovich, V. Fridman, A. Gerson-Gurwitz, I. Schumacher, I. Gertsberg, A. Fich, MA. Hoyt, B. Katz, L. Gheber. (2008) Journal of Cell Science 121:2529-392. A. Gerson-Gurwitz, N. Movshovich, K. Moyal, R. Avunie-Masala, V. Fridman, MA. Hoyt, B. Katz, L. Gheber. (2009) Cellular and Molecular Life Sciences 66(2):301-133. V. Fridman, A. Gerson-Gurwitz, N. Movshovich, M. Kupiec, L. Gheber. (2009) EMBO Reports 10(4):387-93