Figure 1

The cell division cycle and its control. The cell cycle is divided into four distinct phases (G1, S, G2, and M). The progression of a cell through the cell cycle is promoted by CDKs, which are positively and negatively regulated by cyclins and CKis, respectively. As shown, cyclin D isoforms interact with CDK4 and CDK6 to drive the progression of a cell through G1. Cyclin D/CDK4,6 complexes phosphorylate pRb, which releases E2F to transcribe genes necessary for cell cycle progression. The association of cyclin E with CDK2 is active at the G1-S transition and directs entry into S-phase. The INK4s bind and inhibit cyclin D-associated kinases (CDK4 and CDK6). The kinase inhibitor protein group of CKi, p21Cip1/Waf-1, p27Kip1, and p57Kip2, negatively regulate cyclin D/CDK4,6 and cyclin E/CDK2 complexes. S-phase progression is directed by the cyclinA/CDK2 complex, and the complex of cyclin A with Cdk1 is important in G2. CDK1/cyclin B is necessary for the entry into mitosis. Curcumin modulates CKis, CDK-cyclin and Rb-E2F complexes to render G1-arrest and alters CDK/cyclin B complex formation to block G2/M transition.