Strahl T, Gille H, Shaw P E
Spemann Laboratories, Max-Planck-Institut für Immunbiologie, Freiburg, Germany.
Proc Natl Acad Sci U S A. 1996 Oct 15;93(21):11563-8. doi: 10.1073/pnas.93.21.11563.
Mitogenic and stres signals results in the activation of extracellular signal-regulated kinases (ERKs) and stress-activated protein kinase/c-Jun N-terminal kinases (SAPK/JNKs), respectively, which are two subgroups of the mitogen-activated protein kinases. A nuclear target of mitogen-activated protein (MAP) kinases is the ternary complex factor Elk-1, which underlies its involvement in the regulation of c-fos gene expression by mitogenic and stress signals. A second ternary complex factor, Sap1a, is coexpressed with Elk-1 in several cell types and shares attributes of Elk-1, the significance of which is not clear. Here we show that Sap1a is phosphorylated efficiently by ERKs but not by SAPK/JNKs. Serum response factor-dependent ternary complex formation by Sap1a is stimulated by ERK phosphorylation but not by SAPK/JNKs. Moreover, Sap1a-mediated transcription is activated by mitogenic signals but not by cell stress. These results suggest that Sap1a and Elk-1 have distinct physiological functions.
促分裂原和应激信号分别导致细胞外信号调节激酶（ERKs）和应激激活蛋白激酶/c-Jun氨基末端激酶（SAPK/JNKs）的激活，它们是丝裂原激活蛋白激酶的两个亚组。丝裂原激活蛋白（MAP）激酶的一个核靶点是三元复合因子Elk-1，它参与了有丝分裂原和应激信号对c-fos基因表达的调控。第二个三元复合因子Sap1a在几种细胞类型中与Elk-1共表达，并具有Elk-1的一些特性，但其意义尚不清楚。在这里，我们表明Sap1a能被ERKs有效磷酸化，而不能被SAPK/JNKs磷酸化。Sap1a依赖血清反应因子的三元复合物形成受到ERK磷酸化的刺激，而不受SAPK/JNKs的刺激。此外，Sap1a介导的转录由促分裂原信号激活，而不是由细胞应激激活。这些结果表明Sap1a和Elk-1具有不同的生理功能。
