Regulation of Caenorhabditis elegans MCAK by Aurora Kinase Phosphorylation

Abstract

Regulation of microtubule dynamics is essential for many cellular processes, including proper assembly and function of the mitotic spindle. One mechanism for temporal and spatial regulation of microtubule dynamics is provided by the kinesin-13 microtubule depolymerizing enzymes, among which MCAK is the most extensively studied. Vertebrates MCAK locates to chromatin, kinetochores, spindle poles, microtubule tips, and the cytoplasm, implying that the regulation of MCAK activity and subcellular targeting is complex. It has been established that MCAK activity and subcellular localization is regulated by Aurora kinase phosphorylation. However, the in vivo regulatory mechanism is highly complex and is still not fully understood. In this thesis I describe the function and regulation of KLP-7, the C. elegans kinesin-13 homologue. KLP-7 locates to chromosomes and spindle poles during meiosis and mitosis, and to the chromosomal passenger complex region in meiosis. Loss of KLP-7 results in meiotic and mitotic defects that are consistent with an increase in the amount of microtubules in the cytoplasmic and spindle regions of meiotic embryos, and an increase in the number of microtubules emanating from centrosomes. I found that KLP-7 protein is phosphorylated in vivo and in vitro. Finally, by performing a structure-function analysis I identified S546 as a putative Aurora kinase site essential for KLP-7 activity in vivo.