Hengartner C J, Thompson C M, Zhang J, Chao D M, Liao S M, Koleske A J, Okamura S, Young R A
Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142, USA.
Genes Dev. 1995 Apr 15;9(8):897-910. doi: 10.1101/gad.9.8.897.
RNA polymerase II holoenzymes have been described that consist of RNA polymerase II, a subset of general transcription factors, and four SRB proteins. The SRB proteins, which were identified through a selection for genes involved in transcription initiation by RNA polymerase II in vivo, are a hallmark of the holoenzyme. We report here the isolation and characterization of additional SRB genes. We show that the products of all nine SRB genes identified thus far are components of the RNA polymerase II holoenzyme and are associated with a holoenzyme subcomplex termed the mediator of activation. The holoenzyme is capable of responding to a transcriptional activator, suggesting a model in which activators function, in part, through direct interactions with the holoenzyme. Immunoprecipitation experiments with anti-SRB5 antibodies demonstrate that the acidic activating domain of VP16 specifically binds to the holoenzyme. Furthermore, the holoenzyme and the mediator subcomplex bind to a VP16 affinity column. These results provide a more complete description of the RNA polymerase II holoenzyme and suggest that this form of the transcription apparatus can be recruited to promoters via direct interactions with activators.
已有研究描述了RNA聚合酶II全酶，它由RNA聚合酶II、一组通用转录因子以及四种SRB蛋白组成。SRB蛋白是通过在体内筛选参与RNA聚合酶II转录起始的基因而鉴定出来的，是全酶的一个标志。我们在此报告另外一些SRB基因的分离与特性。我们表明，迄今鉴定出的所有九个SRB基因的产物都是RNA聚合酶II全酶的组分，并与一个称为激活介质的全酶亚复合物相关联。全酶能够对转录激活因子作出反应，这提示了一种模型，即激活因子部分地通过与全酶的直接相互作用发挥功能。用抗SRB5抗体进行的免疫沉淀实验表明，VP16的酸性激活结构域特异性地结合全酶。此外，全酶和介质亚复合物结合到VP16亲和柱上。这些结果对RNA聚合酶II全酶进行了更完整的描述，并表明这种形式的转录装置可以通过与激活因子的直接相互作用被募集到启动子上。
