Background

Cell cycle and cell division lie at the heart of cell biology. To build multicellular organism, cell duplication is necessary to generate specialized cells, which can execute particular function. The normal cell cycle is composed of interphase (G1, S and G2 phase) and mitotic (M) phase (Rodríguez-Ubreva et al., 2010; Léger et al., 2016). During interphase, the genetic materials are duplicated and make everything ready for mitosis. Whereas, during mitotic phase, the duplicated chromosomes are segregated and distributed into daughter cells (Sakaue-Sawano et al., 2008).

To precisely preserve genetic information, cell cycle progression must be tightly regulated. Cyclin/CDK complexes control the cell cycle progression through rapidly promoting activities at their respective stages, and are quickly inactivated when their stages are completed (Graña and Reddy, 1995).

Cell synchronization is particularly useful for investigating a cell-cycle regulated event. Using different methods, cells could be synchronized at different cell cycle stage. Treatment of nocodazole, which is an inhibitor of microtubule formation, could synchronize cells at G2/M phase (Ho et al., 2001), while, hydroxyurea, a dNTP synthesis inhibitor, synchronize cells at early S phase (Koç et al., 2004). As an Inhibitor of DNA synthesis (Schvartzman et al., 1984), thymidine can arrest cell at G1/S boundary. Here, we describe a detail method to synchronize cells at G1/S boundary by thymidine (Chen et al., 2018).