Oelgeschläger T, Tao Y, Kang Y K, Roeder R G
Laboratory of Biochemistry and Molecular Biology, Rockefeller University, New York, New York 10021, USA.
Mol Cell. 1998 May;1(6):925-31. doi: 10.1016/s1097-2765(00)80092-1.
In contrast to previous findings in cell-free systems reconstituted with partially purified metazoan factors, we demonstrate dramatic activation of transcription in a TBP-dependent but TAFII-independent manner in HeLa nuclear extracts immunodepleted of TBP and major TAFIIs. Single-round transcription assays reveal that TAFII-independent activation is manifested at the level of productive preinitiation complex formation and that TAFIIs actually impair functional preinitiation complex assembly in a core promoter-specific manner. Furthermore, TAFIIs appear to elevate absolute levels of transcription under multiple-round transcription conditions, presumably by facilitating secondary initiation events. Finally, human coactivator activities related to those in yeast RNA polymerase II/mediator complexes appear to function in unfractionated HeLa nuclear extracts.
与之前在使用部分纯化的后生动物因子重构的无细胞系统中的发现相反，我们证明，在免疫去除了TBP和主要TAFIIs的HeLa细胞核提取物中，转录以依赖TBP但不依赖TAFII的方式被显著激活。单轮转录分析表明，不依赖TAFII的激活表现在有活性的起始前复合物形成水平，并且TAFII实际上以核心启动子特异性方式损害功能性起始前复合物的组装。此外，在多轮转录条件下，TAFII似乎通过促进二次起始事件来提高转录的绝对水平。最后，与酵母RNA聚合酶II/中介体复合物中相关的人类共激活因子活性似乎在未分级的HeLa细胞核提取物中发挥作用。
