Phosphorylation of proteins involved in the G1/S transition by Cyclin A:Cdk2 Active Cyclin A:Cdk2 complexes phosphorylate and inactivate proteins required for maintaining the G1/S phase including: Cdh1, RB1, p21 and p27. All this creates auto-amplification loops that render Cdk2 increasingly more active. In G2, Cdk2, in association with cyclin A, phosphorylates E2F1 and E2F3 resulting in the inactivation and possibly degradation of these two transcription factors (Dynlacht et al., 1994; Krek et al., 1994). Authored: Pagano, M, 2006-09-19 08:23:10 Edited: Matthews, L, 2006-09-28 04:25:14 Pubmed10323868 Pubmed10375532 Pubmed12730199 Pubmed16582612 Reactome Database ID Release 43187948 Reactome, http://www.reactome.org ReactomeREACT_9007 Reviewed: Coqueret, O, 2006-10-06 08:59:06 Cyclin A:Cdk2:substrate complex Cyclin A:Cdk2:phosphorylated substrate complex