Cowell I G, Hurst H C
Department of Biochemistry and Genetics, Medical School, University of Newcastle Upon Tyne, UK.
Nucleic Acids Res. 1994 Jan 11;22(1):59-65. doi: 10.1093/nar/22.1.59.
The bZIP factor E4BP4 overlaps in DNA binding site specificity with the transcriptional activator CREB and members of the ATF family of transcription factors, but is an active transcriptional repressor. In this study we have mapped the repressing activity of E4BP4 to a small 'domain' of 65 amino acids that retains its ability to repress transcription when transferred to the heterologous DNA binding domain of the yeast transcriptional activator GAL4. This segment of the E4BP4 polypeptide contains a high proportion of charged amino acids and does not resemble the repression domains that have been characterized so far from other active transcriptional repressors such as the Drosophila Krüppel, Engrailed or Even-skipped proteins. A mutation which changes the charge configuration of this repression module resulted in a complete loss of repressor activity. The E4BP4-GAL4 fusion protein is able to repress the residual transcription from minimal promoters containing the adenovirus E4 or E1b TATA box. This is consistent with a mechanism of action whereby E4BP4 interacts with some component of the general transcription machinery to cause repression of basal and activated transcription. Although a number of nuclear proteins are able to interact with the E4BP4 repression domain in vitro, these proteins do not appear to include the general transcription factors TFIIB or TBP.
碱性亮氨酸拉链因子E4BP4在DNA结合位点特异性方面与转录激活因子CREB以及转录因子ATF家族成员存在重叠，但它是一种活性转录抑制因子。在本研究中，我们已将E4BP4的抑制活性定位到一个由65个氨基酸组成的小“结构域”，当将其转移至酵母转录激活因子GAL4的异源DNA结合结构域时，该结构域仍保留其抑制转录的能力。E4BP4多肽的这一片段含有高比例的带电荷氨基酸，与迄今已鉴定的其他活性转录抑制因子（如果蝇的Krüppel、Engrailed或Even-skipped蛋白）的抑制结构域不同。一个改变该抑制模块电荷构型的突变导致抑制活性完全丧失。E4BP4-GAL4融合蛋白能够抑制含有腺病毒E4或E1b TATA框的最小启动子的残余转录。这与一种作用机制相一致，即E4BP4与通用转录机制的某些成分相互作用，从而导致基础转录和激活转录受到抑制。尽管许多核蛋白在体外能够与E4BP4抑制结构域相互作用，但这些蛋白似乎不包括通用转录因子TFIIB或TBP。
