Microtubule Organizing Center - Centrosomes

Centrosomes

Movements of the microtubules are based on the actions of the centrosome. Each daughter cell after the cessation of mitosis contains one primary MTOC. Before cell division begins, the interphase MTOC replicates to form two distinct MTOCs (now typically referred to as centrosomes). During cell division, these centrosomes move to opposite ends of the cell and nucleate microtubules to help form the mitotic/meiotic spindle. If the MTOC does not replicate, the spindle cannot form, and mitosis ceases prematurely. Refer to centrosome for more detailed information.

y-tubulin is a protein located at the centrosome that nucleates the microtubules by interacting with the tubulin monomer subunit in the microtubule at the minus end. Organization of the microtubules at the MTOC, or centrosome in this case, is determined by the polarity of the microtubules defined by y-tubulin.