Remboutsika E, Jacq X, Tora L
Department of Transcriptional and Post-transcriptional Control of Gene Regulation, Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, BP 163, F-67404 Illkirch Cedex, Communauté Urbaine de Strasbourg, France.
J Biol Chem. 2001 Apr 20;276(16):12781-4. doi: 10.1074/jbc.M100481200. Epub 2001 Jan 22.
Preinitiation complex assembly is nucleated by the binding of TFIID to the promoters of protein coding genes transcribed by RNA polymerase II. TFIID is comprised of the TATA-binding protein (TBP) and TBP-associated factors (TAF(II)s). We investigated the transcription properties of TBP and TFIID on chromatin templates. On naked templates both TBP and purified TFIID are able to initiate basal transcription. However, on chromatin templates only TBP mediates transcription initiation in a heat-treated extract, whereas TFIID does not. Moreover, TBP-mediated chromatin transcription is blocked in a nontreated extract. These observations suggest that a chromatin-targeted repressor is present in crude extracts and that chromatin per se is not refractory to transcription mediated by TBP. As TBP can function through TAF(II)-independent and TAF(II)-dependent pathways, the repression of TBP-mediated basal transcription may be an additional level to the control of Pol II transcription initiation on chromatin.
起始前复合物的组装由TFIID与RNA聚合酶II转录的蛋白质编码基因启动子的结合引发。TFIID由TATA结合蛋白（TBP）和TBP相关因子（TAF(II)）组成。我们研究了TBP和TFIID在染色质模板上的转录特性。在裸露的模板上，TBP和纯化的TFIID都能够起始基础转录。然而，在染色质模板上，只有TBP能在热处理提取物中介导转录起始，而TFIID则不能。此外，TBP介导的染色质转录在未处理的提取物中被阻断。这些观察结果表明，粗提取物中存在一种靶向染色质的阻遏物，并且染色质本身对TBP介导的转录并非难处理。由于TBP可以通过不依赖TAF(II)和依赖TAF(II)的途径发挥作用，TBP介导的基础转录的抑制可能是染色质上Pol II转录起始控制的一个额外层面。
