High resolution

Module 9: Figure cell cycle dynamics

Changes in the level of different cyclin isoforms and p27 during the course of the cell cycle.

Following the addition of growth factors, cyclin D appears first and remains at a high level during the cell cycle. The rise in cyclin D is followed later during G1 by the appearance of cyclin E, which rapidly disappears towards the beginning of DNA synthesis (S phase). Cyclin A begins to appear towards the end of G1, continues to rise during the S phase and then rapidly declines as the cell progresses through G2. Finally, cyclin B begins to appear during the S phase, and this rise continues into the G2 phase before rapidly falling during the mitotic (M) phase. In contrast with these periodic fluctuations in the cyclins, the level of the cyclin-dependent kinase (CDK) inhibitor p27 drops rapidly early in G1 and remains at a low level throughout the cell cycle.