Inactivation of Cyclin E:Cdk2 complexes by p27/p21 PathwayStep4545 PathwayStep4544 PathwayStep4547 PathwayStep4548 PathwayStep4532 PathwayStep4531 PathwayStep4530 PathwayStep4529 PathwayStep4541 PathwayStep4540 PathwayStep4543 PathwayStep4542 PathwayStep4538 PathwayStep4539 PathwayStep4459 Phosphorylation of Cyclin E1:Cdk2 complexes by Myt1 Phosphorylation of Cyclin E2:Cdk2 complexes by Myt1 Dephosphorylation of Cyclin E:Cdk2 complexes by Cdc25A CAK-mediated phosphorylation of Cyclin E:Cdk2 Association of Rb with Cyclin E:Cdk2 complexes Translocation of p27 to the nucleoplasm Translocation of p21 to the nucleus Phosphorylation of Cyclin E:Cdk2 complexes by Wee-1 Translocation of Cyclin E:Cdk2 complex to the nucleus Formation of Cyclin E:Cdk2 complexes Activation of Cdc25A by c-myc Cyclin E associated events during G1/S transition Reactome Database ID Release 4369202 Reactome, http://www.reactome.org ReactomeREACT_1574 The transition from the G1 to S phase is controlled by the Cyclin E:Cdk2 complexes. As the Cyclin E:Cdk2 complexes are formed, the Cdk2 is phosphorylated by the Wee1 and Myt1 kinases. This phosphorylation keeps the Cdk2 inactive. In yeast this control is called the cell size checkpoint control. The dephosphorylation of the Cdk2 by Cdc25A activates the Cdk2, and is coordinated with the cells reaching the proper size, and with the DNA synthesis machinery being ready. The Cdk2 then phosphorylates G1/S specific proteins, including proteins required for DNA replication initiation. The beginning of S-phase is marked by the first nucleotide being laid down on the primer during DNA replication at the early-firing origins Phosphorylation of proteins involved in G1/S transition by active Cyclin E:Cdk2 complexes SCF(Skp2)-mediated degradation of p27/p21 Ubiquitin-Dependent Degradation of Cyclin E