Möws C C, Preiss T, Slater E P, Cao X, Verrijzer C P, van Der Vliet P C, Beato M
Institut für Molekularbiologie und Tumorforschung (IMT), Phillips Universität, Marburg, Germany.
J Steroid Biochem Mol Biol. 1994 Oct;51(1-2):21-32. doi: 10.1016/0960-0760(94)90111-2.
The influence of progesterone receptor (PR) and glucocorticoid receptor (GR) on transcription from the mouse mammary tumour virus (MMTV) promoter was analyzed using cell-free transcription of DNA templates with a G-free cassette. Preincubation of the templates with either PR or GR stimulates the rate of transcription initiation 10-50 fold, whereas the recombinant DNA binding domain of GR is inactive. Mutations that inactivate the nuclear factor I (NFI) binding site, or NFI depletion of the nuclear extract, decrease basal transcription without influencing receptor-dependent induction. Recombinant NFI, but not its DNA-binding domain, restores efficient basal transcription of the depleted extract. Recombinant OTF1 or OTF2, but not the POU domain of OTF1, enhance MMTV transcription independently of NF1. In agreement with this finding, NFI and OTF1 do not cooperate, but rather compete for binding to the wild type MMTV promoter, though they have the potential to bind simultaneously to properly oriented sites. Our results imply the existence of two independent pathways for MMTV transcription: one initiated by NFI and the other dependent on octamer transcription factors. Only the second pathway is stimulated by steroid hormone receptors in vitro.
利用带有无G盒的DNA模板进行无细胞转录，分析了孕酮受体（PR）和糖皮质激素受体（GR）对小鼠乳腺肿瘤病毒（MMTV）启动子转录的影响。用PR或GR对模板进行预孵育可使转录起始速率提高10 - 50倍，而GR的重组DNA结合结构域则无活性。使核因子I（NFI）结合位点失活的突变，或核提取物中NFI的缺失，会降低基础转录，而不影响受体依赖性诱导。重组NFI，而非其DNA结合结构域，可恢复耗尽提取物的高效基础转录。重组OTF1或OTF2，而非OTF1的POU结构域，可独立于NF1增强MMTV转录。与这一发现一致，NFI和OTF1不协同作用，而是竞争与野生型MMTV启动子的结合，尽管它们有可能同时结合到正确定向的位点。我们的结果表明MMTV转录存在两条独立的途径：一条由NFI启动，另一条依赖于八聚体转录因子。在体外，只有第二条途径受类固醇激素受体刺激。
