O'Hagan R C, Tozer R G, Symons M, McCormick F, Hassell J A
Cancer Research Group, Institute for Molecular Biology and Biotechnology, McMaster University, Hamilton, Ontario, Canada.
Oncogene. 1996 Sep 19;13(6):1323-33.
PEA3, a member of the Ets family of transcriptional regulatory proteins, binds to the PEA3 promoter element and stimulates transcription through this site. The activity of the PEA3 element is regulated by mitogens, activated receptor tyrosine kinases, and oncogenic members of the Ras signal transduction pathway. However, it is not clear whether PEA3 mediates transcriptional regulation by these agents because a number of different Ets proteins can functionally interact with the PEA3 element. To specifically learn whether the activity of PEA3 is regulated, we investigated the ability of constitutively-activated Ras (Ha-RasV12) and signaling proteins downstream of Ras to alter PEA3-dependent reporter gene expression in COS cells. Ha-RasV12 and activated proteins in both the extra-cellular regulated kinase (ERK) and the stress-activated protein kinase (SAPK) or Jun N-terminal kinase (JNK) cascades independently stimulated PEA3-mediated gene expression. Ha-RasV12 stimulation of PEA3 activity was reduced by dominant-negative mutants in each of these protein kinase cascades, suggesting that Ras activates PEA3 through both pathways. Furthermore, the ability of unique activators of each kinase cascade to stimulate PEA3-dependent gene expression was selectively reduced by dominant-negative mutants within the homologous but not the heterologous pathway. Hence two distinct mitogen-activated protein kinase (MAPK) cascades regulate PEA3 activity. PEA3 was phosphorylated in vivo at serine residues consistent with the possibility that it may be a direct target of MAPKs.
PEA3是转录调节蛋白Ets家族的成员，它与PEA3启动子元件结合并通过该位点刺激转录。PEA3元件的活性受有丝分裂原、活化的受体酪氨酸激酶以及Ras信号转导途径的致癌成员调节。然而，尚不清楚PEA3是否介导这些因子的转录调节，因为许多不同的Ets蛋白可与PEA3元件发生功能相互作用。为了具体了解PEA3的活性是否受到调节，我们研究了组成型活化的Ras（Ha-RasV12）以及Ras下游的信号蛋白改变COS细胞中PEA3依赖性报告基因表达的能力。Ha-RasV12以及细胞外调节激酶（ERK）和应激激活蛋白激酶（SAPK）或Jun N端激酶（JNK）级联反应中的活化蛋白均独立刺激PEA3介导的基因表达。这些蛋白激酶级联反应中的显性负性突变体均可降低Ha-RasV12对PEA3活性的刺激作用，这表明Ras通过这两条途径激活PEA3。此外，每个激酶级联反应的独特激活剂刺激PEA3依赖性基因表达的能力，会被同源途径而非异源途径中的显性负性突变体选择性降低。因此，两条不同的丝裂原活化蛋白激酶（MAPK）级联反应调节PEA3活性。PEA3在体内丝氨酸残基处发生磷酸化，这与它可能是MAPKs的直接靶点的可能性相符。
