Inactivation of Cyclin E:Cdk2 complexes by p27/p21 During G1, the activity of cyclin-dependent kinases (CDKs) is kept in check by the CDK inhibitors (CKIs) p27 and p21, thereby preventing premature entry into S phase (see Guardavaccaro and Pagano, 2006). The efficient recognition and ubiquitination of p27 by the SCF(Skp2) complex requires the formation of a trimeric complex containing p27 and cyclin E/A:Cdk2. Edited: Matthews, L, 2006-10-02 07:13:54 Pubmed10323868 Pubmed16262255 Pubmed16600864 Reactome Database ID Release 4369562 Reactome, http://www.reactome.org ReactomeREACT_334 p21/p27 Cyclin E:Cdk2 complexes Cyclin E:Cdk2:p21/p27 complex