Myers L C, Gustafsson C M, Hayashibara K C, Brown P O, Kornberg R D
Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305, USA.
Proc Natl Acad Sci U S A. 1999 Jan 5;96(1):67-72. doi: 10.1073/pnas.96.1.67.
Deletion of any one of three subunits of the yeast Mediator of transcriptional regulation, Med2, Pgd1 (Hrs1), and Sin4, abolished activation by Gal4-VP16 in vitro. By contrast, other Mediator functions, stimulation of basal transcription and of TFIIH kinase activity, were unaffected. A different but overlapping Mediator subunit dependence was found for activation by Gcn4. The genetic requirements for activation in vivo were closely coincident with those in vitro. A whole genome expression profile of a Deltamed2 strain showed diminished transcription of a subset of inducible genes but only minor effects on "basal" transcription. These findings make an important connection between transcriptional activation in vitro and in vivo, and identify Mediator as a "global" transcriptional coactivator.
酵母转录调控中介体（Mediator）的三个亚基Med2、Pgd1（Hrs1）和Sin4中的任何一个缺失，都会在体外消除Gal4-VP16介导的激活作用。相比之下，中介体的其他功能，即对基础转录和TFIIH激酶活性的刺激，并未受到影响。对于Gcn4介导的激活作用，发现了不同但重叠的中介体亚基依赖性。体内激活的遗传需求与体外的密切一致。Deltamed2菌株的全基因组表达谱显示，一组可诱导基因的转录减少，但对“基础”转录的影响较小。这些发现建立了体外和体内转录激活之间的重要联系，并将中介体鉴定为一种“全局”转录共激活因子。
