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The role of microtubules in Aurora-B's kinase activity

Publication ,  Thesis Dissertation
Noujaim, M

Cell division is the process by which a single cell divides into two daughter cells. Each of these two daughter cells must inherit one complete copy of the genome. If not, cancer or cell-death occurs. Not surprisingly, then, life has evolved mechanisms for ensuring that cell division is error-free. The mechanisms, broadly termed “checkpoints,” prevent cell division from occurring if mistakes arise or if each daughter cell were not to inherit one copy of the genome. A major molecule involved in regulating the cell division checkpoint is called Aurora-B. Aurora-B can be thought of as a police officer--Aurora-B stops the cell division process whenever mistakes arise and corrects them before allowing cell division to continue. Unfortunately, if Aurora-B itself becomes faulty or error-prone, the police officer is off-duty, and a greater number of errors occur during cell division. For this reason, Aurora-B is commonly found to be aberrant in tumor cells. Consequently, Aurora-B has recently emerged as a main target for a vast range of novel anti-cancer drugs. In order to divide the genome properly, the cell builds a special mechanical scaffold, reminiscent of the scaffolds at construction sites, called the mitotic spindle. The building blocks of this scaffold are called microtubules. Microtubules are also a target of anticancer therapies. Aurora-B interacts with these microtubules in order to perform its role properly. Although significant, this interaction remains elusive for the most part. Here we provide experimental evidence for the importance of these interactions at the spindle midzone during anaphase. Using in vitro kinase assays we show that microtubules sequester AuroraBʼs activity to ensure the efficiency with which crucial microtubule associated substrates are phosphorylated at the spindle midzone. Thus, allowing the unhindered progression of anaphase and the completion of cytokinesis.