Synchronization of HeLa Cells.

HeLa is one of the oldest and most commonly used cell lines in biomedical research. Owing to the ease of which they can be effectively synchronized by various methods, HeLa cells have been used extensively for studying the cell cycle. Here, we describe several protocols for synchronizing HeLa cells from different phases of the cell cycle, including G1 phase using the HMG-CoA reductase inhibitor lovastatin, S phase with a double thymidine block procedure, and G2 phase with the CDK1 inhibitor RO-3306. Cells can also be enriched in mitosis using nocodazole and mechanical shake-off. Releasing the cells from these blocks enables researchers to follow gene expression and other events through the cell cycle. We also describe several protocols, including flow cytometry, BrdU labeling, immunoblotting, and time-lapse microscopy, for validating the synchrony of the cells and monitoring the progression of the cell cycle.