Inhibition of p27Kip1 gene transcription by mitogens.
How mitogens reduce the abundance of the cell cycle inhibitor p27(Kip1) is an important question, and regulation of p27(Kip1) translation and turnover has been described. Here we show that platelet-derived growth factor (PDGF) reduces the activity of the p27(Kip1) promoter and the abundance of the p27(Kip1) transcript in density-arrested mouse fibroblasts. Inhibition of p27(Kip1) gene expression by PDGF required protein synthesis and histone deacetylase activity but not Akt or ERK activity. PDGF increased the expression of c-Myc in the absence but not presence of a histone deacetylase inhibitor, and c-Myc inhibited p27(Kip1) promoter activity when ectopically expressed in fibroblasts. c-Myc targeted the same region of the p27(Kip1) promoter as did PDGF (deletion analysis) and interacted with this region in vivo (chromatin immunoprecipitation assay). Collectively, these findings suggest that c-Myc mediates the inhibitory effects of PDGF on the p27(Kip1) promoter. We also demonstrate reductions in p27(Kip1) mRNA abundance in primary splenocytes exposed to concanavalin A and in T cells exposed to interleukin-2 (IL-2). In contrast to PDGF in fibroblasts, IL-2 required Akt activity for maximal reductions in p27(Kip1) promoter activity and mRNA abundance in T cells. Thus, mitogens repress p27(Kip1) gene transcription in multiple systems and by multiple mechanisms.
Bagui
Tapan K
TK
Molecular Oncology Program, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Drive, Tampa, FL 33612, USA.
Cui
Dongming
D
Roy
Sangita
S
Mohapatra
Subhra
S
Shor
Audrey C
AC
Ma
Le
L
Pledger
W Jackson
WJ
D000818:Animals; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics* / Q000378:metabolism; D005347:Fibroblasts / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D005786:Gene Expression Regulation / Q000187:drug effects; D006655:Histone Deacetylases / Q000378:metabolism; D006877:Hydroxamic Acids / Q000494:pharmacology; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors; D008934:Mitogens / Q000494:pharmacology*; D041681:NIH 3T3 Cells; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D011401:Promoter Regions, Genetic / Q000235:genetics; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D020871:RNA Stability / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D014158:Transcription, Genetic / Q000187:drug effects*
D006877:Hydroxamic Acids; D008934:Mitogens; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010982:Platelet-Derived Growth Factor; D047428:Protein Kinase Inhibitors; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D050760:Cyclin-Dependent Kinase Inhibitor p27; C012589:trichostatin A; D020929:Mitogen-Activated Protein Kinase Kinases; D006655:Histone Deacetylases