The calcineurin-regulated transcription factor, nuclear factor of activated T cells (NFAT), controls many aspects of T cell function. Here, we demonstrate that the calcineurin/NFAT pathway negatively regulates the expression of cyclin-dependent kinase 4 (CDK4). A canonical NFAT binding site was identified and found to be sensitive to calcium signals, FK506/CsA, and histone deacetylase activity and to not require AP-1. Ectopic expression of NFATc2 inhibited the basal activity of the human CDK4 promoter. Additionally, both calcineurin Aα-/- and NFATc2-/- mice had elevated protein levels of CDK4, confirming a negative regulatory role for the calcineurin/NFAT pathway. This pathway may thus regulate the expression of CDK4 at the transcriptional level and control how cells re-enter a resting, nonproliferative state.
Bibliographical noteFunding Information:
We would like to thank John A. Seidman and David Conner for providing the calcineurin Aα −/− mice; Anjana Rao for providing the NFATc2 −/− mice; Meredith Irwin for the expression constructs for E2F 1-4; David Livingston for the expression constructs for E2F 5-6; Roger J. Davis for the expression construct for HA-tagged NFATc4; Gerald R. Crabtree for the expression construct for FLAG-tagged NFATc2 d175 and NFATc1; and Jackie Slavic and Vivien Igras for help with the preparation of the peripheral blood lymphocytes. We would to thank members of the Burakoff, DeCaprio, and Rao laboratories for their helpful discussions throughout this study. This work is supported by National Institutes of Health grant NIH RO1 CA70758 (S.J.B.); National Institutes of Health grant NIHCA 86432 and HL01310 (J.F.M.); Smokeless Tobacco Research Council grant STRC 0791 (J.F.M.). S.B. is an Association for International Cancer Research Fellow; H.R.W. is a Swedish Wenner-Gren Foundation postdoctoral fellow; and A.F.-A. is a University of Colorado Cancer Center Fellow.