Zhang H, Levine M
Department of Molecular and Cell Biology, Division of Genetics and Development, 401 Barker Hall, University of California, Berkeley, CA 94720, USA.
Proc Natl Acad Sci U S A. 1999 Jan 19;96(2):535-40. doi: 10.1073/pnas.96.2.535.
The precellular Drosophila embryo contains approximately 10 well characterized transcriptional repressors. At least half are short-range repressors that must bind within 100 bp of either upstream activators or the core transcription complex to inhibit (or quench) gene expression. The two long-range repressors can function over distances of 1 kilobase or more to silence transcription. Previous studies have shown that three of the five short-range repressors interact with a common corepressor protein, dCtBP. In contrast, the two long-range repressors, Hairy and Dorsal, recruit a different corepressor protein, Groucho. Hairy also was shown to interact with dCtBP, thereby raising the possibility that Groucho and dCtBP are components of a common corepressor complex. To investigate this issue, we have misexpressed wild-type and mutant forms of Hairy in transgenic embryos. Evidence is presented that Hairy-mediated repression depends on the Groucho interaction sequence (WRPW) but not the weak dCtBP motif (PLSLV) present in the native protein. Conversion of the PLSLV motif into an optimal dCtBP interaction sequence (PLDLS) disrupts the activity of an otherwise normal Hairy protein. These results suggest that dCtBP and Groucho mediate separate pathways of transcriptional repression and that the two proteins can inhibit one another when both bind the same repressor.
细胞形成前的果蝇胚胎含有大约10种特征明确的转录抑制因子。其中至少一半是短程抑制因子，它们必须结合在上游激活因子或核心转录复合物的100个碱基对范围内，以抑制（或淬灭）基因表达。两种长程抑制因子可以在1千碱基或更长的距离发挥作用，使转录沉默。先前的研究表明，五种短程抑制因子中的三种与一种共同的辅抑制蛋白dCtBP相互作用。相比之下，两种长程抑制因子，Hairy和Dorsal，招募了一种不同的辅抑制蛋白Groucho。Hairy也被证明与dCtBP相互作用，从而增加了Groucho和dCtBP是共同辅抑制复合物成分的可能性。为了研究这个问题，我们在转基因胚胎中错误表达了野生型和突变型的Hairy。有证据表明，Hairy介导的抑制作用依赖于Groucho相互作用序列（WRPW），而不是天然蛋白质中存在的弱dCtBP基序（PLSLV）。将PLSLV基序转化为最佳的dCtBP相互作用序列（PLDLS）会破坏原本正常的Hairy蛋白的活性。这些结果表明，dCtBP和Groucho介导了不同的转录抑制途径，并且当两种蛋白都结合同一抑制因子时，它们可以相互抑制。
