Maki Kazuhiro, Arai Honoka, Waga Kazuo, Sasaki Ko, Nakamura Fumihiko, Imai Yoichi, Kurokawa Mineo, Hirai Hisamaru, Mitani Kinuko
Department of Hematology, Dokkyo University School of Medicine, Mibu-machi, Shimotsuga-gun, Tochigi 321-0293, Japan.
Mol Cell Biol. 2004 Apr;24(8):3227-37. doi: 10.1128/MCB.24.8.3227-3237.2004.
TEL is an ETS family transcription factor that possesses multiple putative mitogen-activated protein kinase phosphorylation sites. We here describe the functional regulation of TEL via ERK pathways. Overexpressed TEL becomes phosphorylated in vivo by activated ERK. TEL is also directly phosphorylated in vitro by ERK. The inducible phosphorylation sites are Ser(213) and Ser(257). TEL binds to a common docking domain in ERK. In vivo ERK-dependent phosphorylation reduces trans-repressional and DNA-binding abilities of TEL for ETS-binding sites. A mutant carrying substituted glutamates on both Ser(213) and Ser(257) functionally mimics hyperphosphorylated TEL and also shows a dominant-negative effect on TEL-induced transcriptional suppression. Losing DNA-binding affinity through phosphorylation but heterodimerizing with unmodified TEL could be an underlying mechanism. Moreover, the glutamate mutant dominantly interferes with TEL-induced erythroid differentiation in MEL cells and growth suppression in NIH 3T3 cells. Finally, endogenous TEL is dephosphorylated in parallel with ERK inactivation in differentiating MEL cells and is phosphorylated through ERK activation in Ras-transformed NIH 3T3 cells. These data indicate that TEL is a constituent downstream of ERK in signal transduction systems and is physiologically regulated by ERK in molecular and biological features.
TEL是一种ETS家族转录因子，具有多个假定的丝裂原活化蛋白激酶磷酸化位点。我们在此描述了通过ERK途径对TEL的功能调控。过表达的TEL在体内被活化的ERK磷酸化。TEL在体外也能被ERK直接磷酸化。可诱导的磷酸化位点是Ser(213)和Ser(257)。TEL与ERK中的一个共同对接结构域结合。体内ERK依赖性磷酸化降低了TEL对ETS结合位点的反式抑制和DNA结合能力。在Ser(213)和Ser(257)上都携带取代谷氨酸的突变体在功能上模拟了过度磷酸化的TEL，并且对TEL诱导的转录抑制也显示出显性负效应。通过磷酸化丧失DNA结合亲和力但与未修饰的TEL异源二聚化可能是一种潜在机制。此外，谷氨酸突变体在MEL细胞中显性干扰TEL诱导的红细胞分化以及在NIH 3T3细胞中的生长抑制。最后，在分化的MEL细胞中，内源性TEL与ERK失活同时去磷酸化，而在Ras转化的NIH 3T3细胞中通过ERK激活而磷酸化。这些数据表明，TEL是信号转导系统中ERK的下游成分，并且在分子和生物学特性方面受到ERK的生理调控。
