Wright A P, Gustafsson J A
Centre for Biotechnology, Karolinska Institute, Huddinge University Hospital, NOVUM, Sweden.
Proc Natl Acad Sci U S A. 1991 Oct 1;88(19):8283-7. doi: 10.1073/pnas.88.19.8283.
Induction of transcription from a promoter with two upstream glucocorticoid response elements is 10- to 20-fold greater than that from a similar promoter with only one response element. We have shown that interactions involving the major transactivation domain of the glucocorticoid receptor (tau 1) are the sole determinant of such synergistic transactivation by the receptor. The other transactivation domain of the receptor (tau 2) did not mediate synergistic transactivation, and therefore the ability to synergize is operationally distinct from the transactivation function per se. The level of synergistic transactivation observed in vivo can be accounted for by the level of cooperative DNA binding seen in vitro for a glucocorticoid receptor derivative containing only the tau 1 and DNA-binding domains. Cooperative DNA binding was also observed using a tau 1-DNA-binding domain protein, which was expressed in Escherichia coli and extensively purified. Therefore, it is likely that direct protein-protein interactions between tau 1 domains mediate the cooperative DNA binding. The role of cooperative DNA binding for synergistic transactivation in vivo is discussed in relation to other possible mechanisms.
具有两个上游糖皮质激素反应元件的启动子的转录诱导比仅具有一个反应元件的类似启动子的转录诱导高10至20倍。我们已经表明，涉及糖皮质激素受体主要反式激活结构域（tau 1）的相互作用是该受体这种协同反式激活的唯一决定因素。受体的另一个反式激活结构域（tau 2）不介导协同反式激活，因此协同能力在操作上不同于反式激活功能本身。体内观察到的协同反式激活水平可以由体外仅包含tau 1和DNA结合结构域的糖皮质激素受体衍生物的协同DNA结合水平来解释。使用在大肠杆菌中表达并经过大量纯化的tau 1-DNA结合结构域蛋白也观察到了协同DNA结合。因此，tau 1结构域之间直接的蛋白质-蛋白质相互作用可能介导了协同DNA结合。结合其他可能的机制讨论了协同DNA结合在体内协同反式激活中的作用。
