THE MAP KINASE FUS3 ASSOCIATES WITH AND PHOSPHORYLATES THE UPSTREAM SIGNALING COMPONENT STE5
THE MAP KINASE FUS3 ASSOCIATES WITH AND PHOSPHORYLATES THE UPSTREAM SIGNALING COMPONENT STE5
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DOI：
10.1101/gad.8.3.313
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发表时间：
1994-02-01
影响因子：
10.5
通讯作者：
ELION, EA
中科院分区：
文献类型：
--
作者：
KRANZ, JE;SATTERBERG, B;ELION, EA
酿酒酵母 MAP 激酶 Fus3 的激活被认为是通过涉及三种蛋白质连续作用的线性途径发生的：Ste5（一种功能未知的蛋白质）、Ste11（一种 MAPKK 激酶同源物）和 Ste7（一种磷酸化并激活 Fus3 的 MAPK 激酶同源物）。在本报告中，我们提供了 Fus3 激活新机制的证据，该机制涉及与 Ste5 的直接关联，Ste5 是一种预计不会与 Fus3 相互作用的蛋白质。首先，Ste5 的过度表达以等位基因特异性方式抑制 Fus3 点突变，并增加 Fus3 激酶的体外活性。其次，双杂交系统和两种共纯化方法证明了 Ste5 在体内与 Fus3 结合。第三，即使 Fus3 不活跃，并且在缺乏 Ste7 和 Ste11 的菌株中，Ste5 和 Fus3 在信息素刺激之前也会结合。第四，Ste5 在纯化的复合物中被 Fus3 磷酸化，并与其他蛋白激酶共纯化。这些观察结果表明 Ste5 有可能通过将 Fus3 与其激活蛋白激酶结合来促进信号转导。
Activation of the Saccharomyces cerevisiae MAP kinase Fus3 is thought to occur via a linear pathway involving the sequential action of three proteins: Ste5, a protein of unknown function, Ste11, a MAPKK kinase homolog, and Ste7, a MAPK kinase homolog which phosphorylates and activates Fus3. In this report, we present evidence for a novel mechanism of Fus3 activation that involves a direct association with Ste5, a protein not predicted to interact with Fus3. First, overexpression of Ste5 suppresses fus3 point mutations in an allele-specific manner and increases Fus3 kinase activity in vitro. Second, Ste5 associates with Fus3 in vivo as demonstrated by the two-hybrid system and by two methods of copurification. Third, Ste5 and Fus3 associate prior to pheromone stimulation even when Fus3 is inactive, and in strains lacking Ste7 and Ste11. Fourth, Ste5 is phosphorylated by Fus3 in purified complexes and copurifies with an additional protein kinase(s). These observations suggest the possibility that Ste5 promotes signal transduction by tethering Fus3 to its activating protein kinase(s).