Distinct patterns of histone acetyltransferase and Mediator deployment at yeast protein-coding genes

The transcriptional co-activators Mediator and two histone acetyltransferase (HAT) complexes, NuA4 and SAGA, play global roles in transcriptional activation. Here we explore the relative contributions of these factors to RNA polymerase II association at specific genes and gene classes by rapid nuclear depletion of key complex subunits. We show that the NuA4 HAT Esa1 differentially affects certain groups of genes, whereas the SAGA HAT Gcn5 has a weaker but more uniform effect. Relative dependence on Esa1 and Tra1, a shared component of NuA4 and SAGA, distinguishes two large groups of co-regulated growth-promoting genes. In contrast, we show that the activity of Mediator is particularly important at a separate, small set of highly transcribed TATA box-containing genes. Our analysis indicates that at least three distinct combinations of co-activator deployment are used to generate moderate or high transcription levels, and suggests that each may be associated with distinct forms of regulation.转录共激活因子中介体（Mediator）以及两种组蛋白乙酰转移酶（histone acetyltransferase，HAT）复合物NuA4和SAGA，在转录激活过程中发挥全局性作用。本研究通过快速核内降解关键复合物亚基的方法，探究了上述因子对特定基因及基因类别的RNA聚合酶II（RNA polymerase II）结合的相对贡献。研究表明，NuA4的组蛋白乙酰转移酶Esa1对特定基因群存在差异化调控作用，而SAGA的组蛋白乙酰转移酶Gcn5的调控作用较弱但更为均匀。对Esa1以及NuA4与SAGA的共享组分Tra1的相对依赖程度，可区分两大群共同调控的促生长基因。与之相反，我们发现中介体的活性在另一小类高转录的含TATA框（TATA box）基因中尤为重要。本研究分析表明，至少存在三种不同的共激活因子配置组合，用以介导中等或高水平的转录，且每种组合可能对应独特的调控模式。