h-89 and Cell-Transformation--Viral

Lymphocyte proliferation is key to the regulation of the immune system. Cyclin D2 is the first cell cycle protein induced following stimulation through the T-cell receptor, the B-cell receptor or cytokines. The promoter of this cyclin integrates a diverse range of signals. Through investigating the regulation of this promoter by interleukin-2 and phosphatidylinositol 3-kinase, we have identified a role for the transcription factor CREB, cAMP response element-binding protein. Mutation of the CREB-binding site reduced cyclin D2 promoter activity 5-10-fold. CREB-1 is phosphorylated at serine 133, a critical site for activity, in both T cells and Epstein-Barr virus immortalized B cells. The introduction of an S133A mutant of CREB-1 reduces IL-2 induction of cyclin D2 promoter activity, demonstrating a role for this phosphorylation site in promoter activity. Two inhibitors of protein kinase A reduce lymphocyte proliferation and CREB-1 phosphorylation. This study demonstrates that the cyclin D2 promoter is capable of being regulated by PI3K and CREB and identifies CREB-1 and protein kinase A as potential targets for altering lymphocyte proliferation.

Topics: B-Lymphocytes; Blotting, Western; Carbazoles; Cell Proliferation; Cell Transformation, Viral; Cells, Cultured; Cyclic AMP Response Element-Binding Protein; Cyclic AMP-Dependent Protein Kinases; Cyclin D2; Cyclins; Electrophoretic Mobility Shift Assay; Enzyme Inhibitors; Humans; Indoles; Interleukin-2; Isoquinolines; Phosphatidylinositol 3-Kinases; Phosphorylation; Promoter Regions, Genetic; Protein Kinase Inhibitors; Pyrroles; Sulfonamides; T-Lymphocytes; Transcription, Genetic