Schilling L J, Farnham P J
McArdle Laboratory for Cancer Research, University of Wisconsin-Madison Medical School, Wisconsin 53706, USA.
Cell Growth Differ. 1995 May;6(5):541-8.
The mouse dihydrofolate reductase (dhfr) gene possesses a bidirectional promoter that produces functional transcripts in the opposite direction. These opposite strand transcripts encode the Rep-3 gene product, a protein that has homology to DNA mismatch repair enzymes. The core of the bidirectional promoter consists of four consensus binding sites for the transcription factor Sp1. These binding sites have been shown to be important for basal transcription from both the rep-3a and dhfr promoters. Extensive characterization of the dhfr promoter has shown that growth-dependent regulation requires the E2F binding sites that flank the transcription initiation site. Here we show that endogenous rep-3a mRNA and the rep-3a promoter are growth regulated, in a manner very similar to the regulation of the dhfr mRNA and promoter region. However, we find that the E2F sites required for dhfr regulation are dispensible for regulation of the rep-3a promoter. Instead, we have shown that the rep-3a initiation region is critical for the G1S phase-specific activation of this promoter. Gel mobility shift experiments indicate that a member of the Sp1 family of transcription factors binds to the rep-3a initiation region, suggesting that this family of transcription factors may play a role in cell growth control.
小鼠二氢叶酸还原酶(dhfr)基因拥有一个双向启动子,该启动子可在相反方向产生功能性转录本。这些相反链转录本编码Rep-3基因产物,一种与DNA错配修复酶具有同源性的蛋白质。双向启动子的核心由转录因子Sp1的四个共有结合位点组成。这些结合位点已被证明对rep-3a和dhfr启动子的基础转录很重要。对dhfr启动子的广泛表征表明,生长依赖性调节需要位于转录起始位点两侧的E2F结合位点。在这里,我们表明内源性rep-3a mRNA和rep-3a启动子受到生长调节,其方式与dhfr mRNA和启动子区域的调节非常相似。然而,我们发现dhfr调节所需的E2F位点对于rep-3a启动子的调节是可有可无的。相反,我们已经表明rep-3a起始区域对于该启动子的G1S期特异性激活至关重要。凝胶迁移率变动实验表明,Sp1转录因子家族的一个成员与rep-3a起始区域结合,这表明该转录因子家族可能在细胞生长控制中发挥作用。