Rogatsky Inez, Luecke Hans F, Leitman Dale C, Yamamoto Keith R
Department of Cellular and Molecular Pharmacology, University of California, 513 Parnassus Avenue, HSW1201, San Francisco, CA 94143-0450, USA.
Proc Natl Acad Sci U S A. 2002 Dec 24;99(26):16701-6. doi: 10.1073/pnas.262671599. Epub 2002 Dec 12.
Members of the mammalian p160 family, such as GRIP1, are known as glucocorticoid receptor (GR) coactivators; at certain glucocorticoid response elements (GREs), however, GRIP1 acts as a GR corepressor. We characterized functional interactions of GR and GRIP1 in a repression complex where GR tethers to DNA-bound activator protein-1 (AP-1), as at the human collagenase-3 gene, and tested whether the identified interactions were similar or different at other response elements. At the AP-1 tethering GRE, we mapped the GRIP1 corepressor activity to a domain distinct from the two known GRIP1 activation domains; it exhibited intrinsic GR-independent repression potential when recruited to DNA via Gal4 DNA-binding domain. Interestingly, neither the domain nor the activity was detected in the other two p160 family members, SRC1 and RAC3. The same GRIP1 corepression domain was required for GR-mediated repression at the nuclear factor-kappaB (NF-kappaB) tethering GRE of the human IL-8 gene. In contrast, at the osteocalcin gene GRE, where GR represses transcription by binding to a DNA site overlapping the TATA box, both GRIP1 and SRC1 corepressed, and the GRIP1-specific repression domain was dispensable. Thus, in a single cell type, GR and GRIP1 conferred one mode of activation and two modes of repression by selectively engaging distinct surfaces of GRIP1 in a response element-specific manner.
哺乳动物p160家族的成员，如GRIP1，被认为是糖皮质激素受体（GR）的共激活因子；然而，在某些糖皮质激素反应元件（GREs）处，GRIP1却作为GR的共抑制因子发挥作用。我们对GR和GRIP1在一种抑制复合物中的功能相互作用进行了表征，在这种复合物中，GR与结合在DNA上的激活蛋白-1（AP-1）相连，就像在人胶原酶-3基因中那样，并且测试了在其他反应元件处鉴定出的相互作用是相似还是不同。在AP-1相连的GRE处，我们将GRIP1的共抑制因子活性定位到一个与两个已知的GRIP1激活结构域不同的结构域；当通过Gal4 DNA结合结构域被招募到DNA上时，它表现出内在的不依赖GR的抑制潜能。有趣的是，在另外两个p160家族成员SRC1和RAC3中未检测到该结构域和活性。在人白细胞介素-8基因的核因子-κB（NF-κB）相连的GRE处，GR介导的抑制也需要相同的GRIP1共抑制结构域。相比之下，在骨钙素基因的GRE处，GR通过与重叠TATA框的DNA位点结合来抑制转录，GRIP1和SRC1都发挥共抑制作用，并且GRIP1特异性的抑制结构域是可有可无的。因此，在单一细胞类型中，GR和GRIP1通过以反应元件特异性的方式选择性地与GRIP1的不同表面结合，赋予了一种激活模式和两种抑制模式。
