Mitogenic regulation of p27(Kip1) gene is mediated by AP-1 transcription factors.
The abundance of cyclin-dependent kinase inhibitor p27(Kip1) during the cell cycle determines whether cells will proliferate or become quiescent. Although the post-translational regulation of p27(Kip1) is well established, its transcriptional regulation is poorly understood. Here, we report that mitogenic stimulation of quiescent HEK293 and Huh7 cells showed a rapid decline in the levels of p27(Kip1) transcript by 2.4 +/- 0.1-fold. Inhibition of the p27(Kip1) gene in response to mitogens involved transcriptional down-regulation and required newly synthesized protein(s). Mutation of the AP-1 element at position -469 in the human p27(Kip1) promoter abrogated the effect of mitogens. The recruitment of the AP-1 complex to the p27(Kip1) promoter was confirmed by in vitro DNA binding and chromatin immunoprecipitation studies. Reporter gene analysis combined with enforced expression of Jun/Fos proteins suggested the involvement of Jun/Fos heterodimer in the transrepression process. Both MAPK and phosphatidylinositol 3-kinase signaling pathways appeared to mediate p27(Kip1) transcription. Furthermore, hepatitis B virus X protein-mediated down-regulation of p27(Kip1) in a transgenic environment correlated with an increase in c-Fos levels, reiterating the physiological relevance of AP-1 in the transcriptional regulation of p27(Kip1). Collectively, our studies present the first evidence demonstrating the role of the AP-1 complex in transcriptional down-regulation of the p27(Kip1) gene following mitogenic stimulation.
Khattar
Ekta
E
Virology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India.
Kumar
Vijay
V
D015153:Blotting, Western; D002460:Cell Line; D045744:Cell Line, Tumor; D047369:Chromatin Immunoprecipitation; D002867:Chromones / Q000494:pharmacology; D019295:Computational Biology; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000235:genetics / Q000378:metabolism*; D024202:Electrophoretic Mobility Shift Assay; D005419:Flavonoids / Q000494:pharmacology; D005434:Flow Cytometry; D006801:Humans; D048369:MAP Kinase Kinase 1 / Q000037:antagonists & inhibitors / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics / Q000502:physiology; D055503:Protein Multimerization / Q000235:genetics / Q000502:physiology; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics / Q000378:metabolism; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D018808:Transcription Factor AP-1 / Q000235:genetics / Q000502:physiology*
D002867:Chromones; D050760:Cyclin-Dependent Kinase Inhibitor p27; D005419:Flavonoids; D048369:MAP Kinase Kinase 1; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D016760:Proto-Oncogene Proteins c-fos; D016755:Proto-Oncogene Proteins c-jun; D034741:RNA, Small Interfering; D013755:Tetradecanoylphorbol Acetate; D018808:Transcription Factor AP-1; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one