Definition: Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.
Input: To study the mechanism of centrosome duplication in cycling cells, we established a novel system of multiple centrosome formation in two types of cells: CHO cells treated with RO3306, a Cyclin-dependent kinase 1 (Cdk1) inhibitor and DT40 cells, in which Cdks were knocked out by chemical genetics. Cdk1-inactivated cells initiated DNA replication and centrosome duplication at the onset of S phase. They became arrested at the end of G2, but the centrosome cycle continued to produce supernumerary centrioles/centrosomes without DNA endoreplication in those cells. Centrosomes were amplified in a highly synchronous and reproducible manner: all of them were located next to the nucleus and spread widely apart from each other with several m in distance. Double knockout of Cdk1 and Cdk2 caused cell cycle arrest at G1/S and centrosomes were no longer duplicated. However, cells continued to grow and increased their volume over 10-fold during 48 hr of culture. Centrosome components, including -tubulin and Cep135, were synthesized and accumulated during the arrest, allowing rapid centrosome multiplication upon recovery from the cell cycle arrest or expression of exogenous Plk4 in G1/S cells. Thus centrosome amplification results from the discoordination of the centrosome cycle from the progression of other cell cycle events, which is controlled by different levels of Cdk activities.
