title: Activation of mitogen-activated protein kinase cascade regulates pituitary tumor-transforming gene transactivation function.
abstract: Pituitary tumor-transforming gene (PTTG) is a recently characterized oncogene that can act as a transcriptional activator. In this study, we have characterized the transactivation domain of PTTG. Transient transfection of fusion constructs containing GAL4 DNA-binding domain and different parts of PTTG indicated the transactivation domain of PTTG is located between amino acids 119 and 164. Mitogen-activated protein (MAP) kinase cascade is important in the regulation of cell growth, apoptosis, and differentiation. Therefore, we have explored the possibility that this kinase cascade plays a role in regulating PTTG transactivation function. Activation of the MAP kinase cascade by epidermal growth factor or an expression vector for a constitutively active form of the MAP kinase kinase (MEK1) led to stimulation of PTTG transactivation activity. We showed that PTTG is phosphorylated in vitro on Ser(162) by MAP kinase and that this phosphorylation site plays an essential role in PTTG transactivation function. We demonstrated that PTTG interacts directly with MEK1 through a putative SH3 domain-binding site located between amino acids 51 and 54 and that this interaction is crucial for PTTG transactivation function. In addition, we showed that activation of MAP kinase phosphorylation cascade resulted in nuclear translocation of PTTG. Together, our data establish that a growth factor-stimulated MAP kinase plays an important role in modulating PTTG function.
authors.affiliation: Division of Endocrinology and Metabolism, Cedars-Sinai Research Institute-UCLA School of Medicine, Los Angeles, California 90048, USA. pei@cshs.org
authors.forename: L
authors.initials: L
authors.lastname: Pei
mesh_terms: D016475:3T3 Cells; D020816:Amino Acid Motifs; D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D002467:Cell Nucleus / Q000378:metabolism; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000378:metabolism; D005982:Glutathione Transferase / Q000378:metabolism; D048369:MAP Kinase Kinase 1; D020935:MAP Kinase Signaling System; D051379:Mice; D008856:Microscopy, Fluorescence; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D009363:Neoplasm Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D017354:Point Mutation; D011233:Precipitin Tests; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D064249:Securin; D015398:Signal Transduction; D015533:Transcriptional Activation; D014162:Transfection; D018909:src Homology Domains
chemical_list: D009363:Neoplasm Proteins; D011993:Recombinant Fusion Proteins; D064249:Securin; D004815:Epidermal Growth Factor; D005982:Glutathione Transferase; D017346:Protein Serine-Threonine Kinases; D048369:MAP Kinase Kinase 1; C482127:Map2k1 protein, mouse; D020929:Mitogen-Activated Protein Kinase Kinases