A permissive role for phosphatidylinositol 3-kinase in the Stat5-mediated expression of cyclin D2 by the interleukin-2 receptor.
The interleukin-2 (IL-2) receptor promotes T cell proliferation in part by inducing the expression of D-type cyclins, which enable cells to progress from the G1 to S phase of the cell cycle. We previously showed that the IL-2 receptor induces expression of cyclin D2 by activating the transcription factor Stat5, which binds directly and immediately to a site upstream of the cyclin D2 promoter. We show here that subsequent transcription of the cyclin D2 gene occurs by a delayed, cycloheximide-sensitive mechanism, which implies the involvement of additional regulatory mechanisms. The transcription factor c-Myc is induced by Stat5 and is reported to bind to two E box motifs in the cyclin D2 promoter. However, in IL-2-stimulated T cells, c-Myc does not appear to be involved in cyclin D2 induction, since we found that these two E boxes are preferentially bound by USF-1 and USF-2 and, moreover, are dispensable for cyclin D2 promoter activity. Instead, we found that Stat5 activates the phosphatidylinositol 3-kinase (PI3 kinase) pathway by a delayed, cycloheximide-sensitive mechanism and that PI3 kinase activity is essential for the induction of cyclin D2 by Stat5. Chromatin immunoprecipitation experiments revealed that PI3 kinase is required for the optimal binding of RNA polymerase II to the promoters of cyclin D2 as well as other genes. Our results reveal a novel link between PI3 kinase and RNA polymerase II promoter binding activity and demonstrate discrete, coordinated roles for the PI3 kinase and Stat5 pathways in cyclin D2 transcription.
Moon
James J
JJ
Department of Immunology, University of Washington School of Medicine, Seattle, Washington 98195, USA.
Rubio
Eric D
ED
Martino
Anthony
A
Krumm
Anton
A
Nelson
Brad H
BH
D021581:Active Transport, Cell Nucleus; D020816:Amino Acid Motifs; D000818:Animals; D001665:Binding Sites; D015152:Blotting, Northern; D015153:Blotting, Western; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D002843:Chromatin / Q000378:metabolism; D056742:Cyclin D2; D016213:Cyclins / Q000096:biosynthesis* / Q000737:chemistry / Q000378:metabolism; D003513:Cycloheximide / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D004247:DNA / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000378:metabolism*; D017930:Genes, Reporter; D006801:Humans; D007376:Interleukin-2 / Q000378:metabolism; D051379:Mice; D008894:Milk Proteins; D019869:Phosphatidylinositol 3-Kinases / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D012319:RNA Polymerase II / Q000378:metabolism; D015375:Receptors, Interleukin-2 / Q000378:metabolism*; D050799:STAT5 Transcription Factor; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism*; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic; D051720:Upstream Stimulatory Factors
C080336:CCND2 protein, human; C486196:Ccnd2 protein, mouse; D002843:Chromatin; D056742:Cyclin D2; D016213:Cyclins; D004268:DNA-Binding Proteins; D007376:Interleukin-2; D008894:Milk Proteins; D016271:Proto-Oncogene Proteins c-myc; D015375:Receptors, Interleukin-2; D050799:STAT5 Transcription Factor; D015534:Trans-Activators; D014157:Transcription Factors; C497181:USF1 protein, human; D051720:Upstream Stimulatory Factors; C497183:Usf1 protein, mouse; D004247:DNA; D003513:Cycloheximide; D019869:Phosphatidylinositol 3-Kinases; D012319:RNA Polymerase II