Studies on biological roles of CEP215, a centrosome component, during the cell cycle

Abstract

In most animal cells, the centrosome functions as a major microtubule organizing center and controls cellular morphology, migration, subcellular transport and cell division. Understanding the functional mechanisms of this mysterious and interesting organelle at the molecular level has been a great topic in molecular and cellular biology. Meanwhile, proteomic analysis revealed that human centrosome is composed of several hundred kinds of proteins. The composition of the centrosome changes dynamically during the cell cycle. Among the centrosomal proteins, I focused on the functional mechanisms of CEP215, an important pericentriolar material component, for microtubule nucleation and centrosome maturation during interphase and mitosis, respectively. In chapter 1, I investigated the knockdown phenotypes of CEP215 during interphase. It has been reported that CEP215 is involved in several centrosome behaviors such as centrosome cohesion, microtubule nucleation and centrosome maturation. However, the precise mechanisms of these functions have not been thoroughly explored. Thus, I focused on biological roles of CEP215 for microtubule nucleation in interphase. The results revealed that the physical interaction of CEP215 with γ-tubulin is essential for the microtubule nucleation in interphase cells. In chapter 2, I investigated roles of CEP215 in mitotic cells. From chapter 1, I found that CEP215 physically interacts with γ-tubulin in interphase cells. Here, I hypothesized that the interaction of CEP215 with γ-tubulin also contributes to the centrosome maturation during mitosis. It was unexpected that the physical interaction of CEP215 with γ-tubulin is not necessary for the centrosome maturation. Rather, physical interaction of CEP215 with pericentrin is critical for the centrosome maturation and subsequent proper bipolar spindle formation during mitosis. The present results provide an insight into how pericentriolar material components are assembled to form a spindle pole during mitosis.