When cells divide more rapidly than every 60 minutes, a replication cycle is initiated before the end of the preceding division cycle.

TLS Online TPP Program

#Id: 8872

#Unit 2. Cellular Organization

The entire process of mitotic CDKs activation and entry into mitosis involves two positive feedback loops and coordination between events at the centrosome, in the cytoplasm, and in the nucleus.

TLS Online TPP Program

#Id: 8873

#Unit 2. Cellular Organization

Cdc25B, activating an initial small pool of cyclin B/1 at the centrosome, which is facilitate centrosome maturation.

TLS Online TPP Program

#Id: 8874

#Unit 2. Cellular Organization

Initial pool of active cyclin B-CDK1 phosphorylates Cdc25C, this recruits Pin1 and Plk1, which recognize Cdc25C through their phospho-binding domains. 

TLS Online TPP Program

#Id: 8875

#Unit 2. Cellular Organization

Pin1 and Plk1 modify and phosphorylate Cdc25C to stimulate its phosphatase activity

TLS Online TPP Program

#Id: 8877

#Unit 2. Cellular Organization

The pool of active Cdc25C is created, that activates the large pool of cytosolic cyclin B-CDK1, which activates more cytosolic Cdc25C as part of positive feedback loop 1

TLS Online TPP Program

#Id: 8878

#Unit 2. Cellular Organization

At the same time that Cdc25C is being activated, mitotic CDKs and Plk1 phosphorylate Wee1, which targets it for destruction through a phosphobinding SCF protein-ubiquitin ligase. This forms positive feedback loop 2