Zhu Xuefeng, Wirén Marianna, Sinha Indranil, Rasmussen Nina N, Linder Tomas, Holmberg Steen, Ekwall Karl, Gustafsson Claes M
Department Laboratory Medicine, Karolinska Institutet, Novum, SE-141 86 Stockholm, Sweden.
Mol Cell. 2006 Apr 21;22(2):169-78. doi: 10.1016/j.molcel.2006.03.032.
Mediator exists in a free form containing the Med12, Med13, CDK8, and CycC subunits (the Srb8-11 module) and a smaller form, which lacks these four subunits and associates with RNA polymerase II (Pol II), forming a holoenzyme. We use chromatin immunoprecipitation (ChIP) and DNA microarrays to investigate genome-wide localization of Mediator and the Srb8-11 module in fission yeast. Mediator and the Srb8-11 module display similar binding patterns, and interactions with promoters and upstream activating sequences correlate with increased transcription activity. Unexpectedly, Mediator also interacts with the downstream coding region of many genes. These interactions display a negative bias for positions closer to the 5' ends of open reading frames (ORFs) and appear functionally important, because downregulation of transcription in a temperature-sensitive med17 mutant strain correlates with increased Mediator occupancy in the coding region. We propose that Mediator coordinates transcription initiation with transcriptional events in the coding region of eukaryotic genes.
中介体以自由形式存在，包含Med12、Med13、CDK8和CycC亚基（Srb8 - 11模块）以及一种较小的形式，后者缺乏这四个亚基并与RNA聚合酶II（Pol II）结合，形成全酶。我们使用染色质免疫沉淀（ChIP）和DNA微阵列来研究裂殖酵母中介体和Srb8 - 11模块在全基因组范围内的定位。中介体和Srb8 - 11模块显示出相似的结合模式，并且与启动子和上游激活序列的相互作用与转录活性增加相关。出乎意料的是，中介体还与许多基因的下游编码区域相互作用。这些相互作用对靠近开放阅读框（ORF）5'端的位置呈现负偏向，并且似乎在功能上很重要，因为在温度敏感的med17突变菌株中转录下调与中介体在编码区域的占有率增加相关。我们提出中介体协调真核基因编码区域中的转录起始与转录事件。
