Synchronization of HeLa Cells to Various Interphases Including G1, S, and G2 Phases

The typical cell cycle in eukaryotes is composed of four phases including the G1, S, G2, and M phases. G1, S, and G2 together are called interphase. Cell synchronization is a process that brings cultured cells at different stages of the cell cycle to the same phase, which allows the study of phase-specific cellular events. While interphase cells can be easily distinguished from mitotic cells by examining their chromosome morphology, it is much more difficult to separate and distinguish the interphases from each other. Here, we describe drug-derived protocols for synchronizing HeLa cells to various interphases of the cell cycle: G1 phase, S phase, and G2 phase. G1 phase synchronization is achieved through serum starvation, S phase synchronization is achieved through a double thymidine block, and G2 phase synchronization is achieved through the release of the double thymidine block followed by roscovitine treatment. Successful synchronization can be assessed using flow cytometry to examine the DNA content and Western blot to examine the expression of various cyclins.