title: The MEK pathway is required for stimulation of p21(WAF1/CIP1) by transforming growth factor-beta.
abstract: Transforming growth factor-beta (TGF-beta)can induce the cyclin-dependent kinase inhibitors p21 and p15 in a variety of cell types. We have shown previously that Smad3 is required for the growth inhibitory activity of TGF-beta, whereas overexpression of Smads is not sufficient to activate the expression of p21 in HaCaT cells. These data suggest that an additional signaling pathway may be involved in stimulating p21 in HaCaT cells. Given the recent finding that the mitogen-activated protein kinase (MAPK) pathway can cause p21 induction and arrest cells, we examined the involvement of this pathway for p21 and p15 induction by TGF-beta. We found that TGF-beta can regulate the MAPK pathway, leading to the increased transactivation ability of transcription factor Elk. Constitutively active components in the MAPK pathway activate p21 expression, and inhibitors or dominant negative constructs for the MAPK pathway significantly decrease p21 induction by TGF-beta. Both constitutively active MEK and inhibitors for MEK have no effect on Smad activity, including DNA binding, localization, and interaction with coactivator p300/CBP. These findings suggest that the MAPK pathway may be an independent pathway that is involved in p21 and p15 induction by TGF-beta.
authors.affiliation: Department of Pharmacology, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: P P
authors.initials: PP
authors.lastname: Hu
authors.forename: X
authors.initials: X
authors.lastname: Shen
authors.forename: D
authors.initials: D
authors.lastname: Huang
authors.forename: Y
authors.initials: Y
authors.lastname: Liu
authors.forename: C
authors.initials: C
authors.lastname: Counter
authors.forename: X F
authors.initials: XF
authors.lastname: Wang
mesh_terms: D016227:Benzoquinones; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000235:genetics / Q000378:metabolism*; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D047029:Lactams, Macrocyclic; D008156:Luciferases / Q000235:genetics / Q000378:metabolism; D048670:MAP Kinase Kinase 4; D048728:MAP Kinase Kinase Kinase 1; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism*; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism; D011809:Quinones / Q000494:pharmacology; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017828:Rifabutin / Q000031:analogs & derivatives; D015398:Signal Transduction / Q000187:drug effects; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D018631:ras Proteins / Q000378:metabolism
chemical_list: D016227:Benzoquinones; C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D004791:Enzyme Inhibitors; D047029:Lactams, Macrocyclic; D011809:Quinones; D011993:Recombinant Fusion Proteins; D016212:Transforming Growth Factor beta; D017828:Rifabutin; C020754:herbimycin; D008156:Luciferases; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D020928:Mitogen-Activated Protein Kinases; D048728:MAP Kinase Kinase Kinase 1; D020930:MAP Kinase Kinase Kinases; C482576:MAP3K1 protein, human; D048670:MAP Kinase Kinase 4; C482559:MAP2K4 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases; D018631:ras Proteins