PT - JOURNAL ARTICLE AU - Olashaw, Nancy AU - Pledger, W. J. TI - Paradigms of Growth Control: Relation to Cdk Activation AID - 10.1126/stke.2002.134.re7 DP - 2002 May 28 TA - Science's STKE PG - re7--re7 VI - 2002 IP - 134 4099 - http://stke.sciencemag.org/content/2002/134/re7.short 4100 - http://stke.sciencemag.org/content/2002/134/re7.full SO - Sci. STKE2002 May 28; 2002 AB - The cyclin-dependent kinases (CDKs) play a key role in cell cycle control, and in this review, we focus on the events that regulate their activities. Emphasis is placed on the CDKs that function during the G1 phase of the cell cycle and on the CDK inhibitor p27Kip1. We discuss how CDK activation relates to two basic concepts of cell cycle regulation: (i) the need for multiple mitogens for the proliferation of nontransformed cells and (ii) the inhibitory effect of high culture density on proliferative capacity. We also describe how Cdk2 modulates the expression of the α subunit of the interleukin-2 receptor in T cells, and address the question of whether p27Kip1 functions as an activator or inhibitor of the CDKs associated with the D cyclins.