Vargas G A, Isas J M, Fantino E, Gargus J J, Haigler H T
Department of Biological Chemistry, University of California Medical School, Irvine, USA.
J Cell Physiol. 1998 Sep;176(3):642-7. doi: 10.1002/(SICI)1097-4652(199809)176:3<642::AID-JCP21>3.0.CO;2-#.
The epidermal growth factor receptor (EGFR) plays a critical role in normal growth and its overexpression is associated with several types of cancer. To learn more about regulation of the expression of this important receptor, we investigated the role of the TAF(II)250 subunit of transcription factor IID in the transcription of the EGFR gene. The EGFR gene has a TATA-less promoter and TAF(II)250 has previously been shown to have an important regulatory role in such promoters. The study was performed in the ts13 hamster cell line which has a temperature-sensitive mutation in the CCG1 gene that encodes TAF(II)250. At the nonpermissive temperature, the transcription of a few cell cycle-dependent genes is depressed in ts13 cells while global RNA synthesis is unaffected. Using this model system, we found that EGFR promoter-driven luciferase expression in transiently transfected ts13 cells decreased 8, 25, and 50-fold after 12, 24, and 48 hours, respectively, at the nonpermissive temperature. The decrease was partially rescued by cotransfection with the wild-type CCG1 gene. The expression of endogenous EGFR also appeared to be regulated by TAF(II)250--the maximum binding capacity of ts13 cells for 125I-labeled EGF decreased approximately twofold when incubated for 2 days at the nonpermissive temperature. Placing these studies in the context of the current understanding of the TFIID transcription complex, we speculate that selective stimulation of EGFR gene transcription may be mediated by TAF(II)250 interaction with enhancer-bound activators and the basal transcription machinery.
表皮生长因子受体（EGFR）在正常生长过程中发挥着关键作用，其过度表达与多种癌症相关。为了更深入了解这一重要受体表达的调控机制，我们研究了转录因子IID的TAF(II)250亚基在EGFR基因转录中的作用。EGFR基因有一个无TATA框的启动子，先前已证明TAF(II)250在这类启动子中具有重要的调控作用。该研究在ts13仓鼠细胞系中进行，该细胞系在编码TAF(II)250的CCG1基因中存在温度敏感突变。在非允许温度下，ts13细胞中一些细胞周期依赖性基因的转录受到抑制，而整体RNA合成不受影响。利用这个模型系统，我们发现，在非允许温度下，瞬时转染的ts13细胞中EGFR启动子驱动的荧光素酶表达在12、24和48小时后分别下降了8倍、25倍和50倍。通过与野生型CCG1基因共转染，这种下降得到了部分挽救。内源性EGFR的表达似乎也受TAF(II)250调控——当在非允许温度下孵育2天时，ts13细胞对125I标记的EGF的最大结合能力下降了约两倍。结合目前对TFIID转录复合物的理解来审视这些研究，我们推测EGFR基因转录的选择性刺激可能是由TAF(II)250与结合增强子的激活剂及基础转录机制的相互作用介导的。
