CDK4 Protein, Human (sf9, His, Flag, Avi)

CDK4 protein serves as the Ser/Thr-kinase component within cyclin D-CDK4 (DC) complexes, orchestrating the phosphorylation and inhibition of members belonging to the retinoblastoma (RB) protein family, including RB1. This regulatory activity is pivotal in controlling the cell cycle during the G(1)/S transition. The phosphorylation of RB1 instigates the dissociation of the transcription factor E2F from the RB/E2F complexes, facilitating the subsequent transcription of E2F target genes that drive progression through the G(1) phase. Particularly notable is the hypophosphorylation of RB1 occurring in early G(1) phase. As essential integrators of diverse mitogenic and antimitogenic signals, cyclin D-CDK4 complexes play a central role in cell cycle regulation. Additionally, CDK4 protein exhibits the capability to phosphorylate SMAD3 in a cell-cycle-dependent manner, thereby repressing its transcriptional activity. CDK4 is a crucial component of the ternary complex, cyclin D/CDK4/CDKN1B, which is indispensable for the nuclear translocation and activity of the cyclin D-CDK4 complex.