Systems biology of the cell cycle

Published on November 4, 2014 Reviewed on January 23, 2022   26 min

Other Talks in the Series: Systems Biology

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My name is Bela Novak, and I am the professor of systems biology at the University of Oxford in the department of biochemistry. I will talk about the systems biology of the eukaryotic cell cycle control.
This slide shows a simple cartoon of the cell cycle. The cycle starts with a cell in G1 phase with unreplicated chromosomes. Although eukaryotes have more than one chromosome, I only show one of them here as a straight gray line. Chromosomes are replicated during S-phase of the cycle, which follows G1 in the cycle. Replication creates two identical sister chromatids, which are held together by cohesin complexes. After another gap phase called G2, the cell enters into mitosis, which is also called M-phase. The goal of M-phase is to separate the two sister chromatids within the cell. Successful separation of sisters requires biorientation of all chromosomes on the bipolar's mitotic spindle during prometaphase of mitosis. Once biorientation is completed, the cell enters into metaphase and segregates the two sister chromatids during anaphase. Finally, the cell divides into two daughter cells and the process can be repeated again depending on the external conditions.
Cell cycle progression is characterized by transitions that the cell decides to enter into the next phase of the cycle. The first decision is in G1 phase and it's called start or restriction point that the cell decides to proliferate or stay quiescent. The G1/S transition marks the initiation of replication. Entry into mitosis is controlled by the G2/M transition. Segregation of sister chromatids is decided before metaphase/anaphase transition takes place. The final decision is exit from mitosis and to divide into two daughter cells. Before each cell cycle transition, the cell has to be sure that conditions are right for the next step. Therefore, each cell cycle transition is a decision-making process.