Cyclins
- G1/S cyclins
- Activate Cdks in late G1
- Help promote passage through restriction point/start in late G1, resulting in commitment to cell cycle entry
- S cyclins
- Bind CDKs soon after progression through start
- Help stimulate chromosome duplication
- M cyclins
- Activate Cdks that stimulate entry into mitosis at G2/M checkpoint
A separate regulatory protein APC/C intiates metaphase-anaphase transition