Schmidt S, Baniahmad A, Eggert M, Schneider S, Renkawitz R
Genetisches Institut der Justus-Liebig Universität Giessen, Heinrich-Buff-Ring 58-62, D-35392 Giessen, Germany.
Nucleic Acids Res. 1998 Mar 1;26(5):1191-7. doi: 10.1093/nar/26.5.1191.
Nuclear hormone receptors are exerting their effect on transcription by interacting with basal factors of the transcription machinery and/or by recruiting intermediary factors, such as the mouse protein GRIP1. GRIP1 is one of the recently identified coactivators for nuclear hormone receptors. Upon interaction with the hormone-binding domain of the receptors, GRIP1 increases their transcriptional activity. Here we show that GRIP1 contains at least two receptor-interacting regions using the hormone-binding domain of several receptors as bait in the yeast two-hybrid assay. GRIP1 interacts in a hormone-dependent manner with the C-termini of nuclear hormone receptors such as GRalpha, TRalpha, TRbeta, RARalpha and RXRalpha but not with v-ErbA. GRIP1 contains several LXXLL motifs which were shown to be required for receptor interaction. A protein fragment containing all of the three LXXLL motifs, but having the activation domain deleted, is able to repress the transcriptional activity of human TRbeta, whereas a region harbouring only one LXXLL motif fails to do so. A protein fragment with two LXXLL motifs exhibits an intermediate modulation of the TRbeta transactivation. While one motif seems to be sufficient for receptor interaction, more than one motif is needed for functional interference.
核激素受体通过与转录机制的基础因子相互作用和/或通过招募中间因子（如小鼠蛋白GRIP1）来发挥其对转录的作用。GRIP1是最近鉴定出的核激素受体共激活因子之一。与受体的激素结合结构域相互作用后，GRIP1会增加其转录活性。在这里，我们通过酵母双杂交实验，以几种受体的激素结合结构域为诱饵，表明GRIP1至少包含两个受体相互作用区域。GRIP1以激素依赖的方式与核激素受体（如GRα、TRα、TRβ、RARα和RXRα）的C末端相互作用，但不与v-ErbA相互作用。GRIP1包含几个LXXLL基序，已证明这些基序是受体相互作用所必需的。一个包含所有三个LXXLL基序但缺失激活结构域的蛋白质片段能够抑制人TRβ的转录活性，而仅包含一个LXXLL基序的区域则不能。一个具有两个LXXLL基序的蛋白质片段对TRβ反式激活表现出中间调节作用。虽然一个基序似乎足以与受体相互作用，但功能干扰需要多个基序。
