The plant corepressor TPL is recruited to diverse chromatin contexts, yet its mechanism of repression remains unclear. Previously, we leveraged the fact that TPL retains its function in a synthetic transcriptional circuit in the yeast model Saccharomyces cerevisiae to localize repressive function to two distinct domains. Here, we employed two unbiased whole-genome approaches to map the physical and genetic interactions of TPL at a repressed locus. We identified SPT4, SPT5, and SPT6 as necessary for repression with SPT4 acting as a bridge connecting TPL to SPT5 and SPT6. We discovered the association of multiple additional constituents of the transcriptional preinitiation complex at TPL-repressed promoters, specifically those involved early in transcription initiation. These findings were validated in yeast and plants, including a novel method to analyze the conditional loss of function of essential genes in plants. Our findings support a model where TPL nucleates preassembly of the transcription activation machinery to facilitate the rapid onset of transcription once repression is relieved.

中文翻译：

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TPL/TBL1 型辅阻遏蛋白的功能是使前起始复合物的组装成核。


植物辅阻遏物 TPL 被募集到不同的染色质环境中，但其抑制机制仍不清楚。以前，我们利用 TPL 在酵母模型酿酒酵母的合成转录回路中保留其功能的事实，将抑制功能定位于两个不同的结构域。在这里，我们采用了两种无偏倚的全基因组方法来绘制 TPL 在抑制基因座的物理和遗传相互作用。我们确定 SPT4 、 SPT5 和 SPT6 是抑制所必需的，其中 SPT4 充当连接 TPL 与 SPT5 和 SPT6 的桥梁。我们发现转录前起始复合物的多个额外成分与 TPL 抑制的启动子相关，特别是那些参与转录起始早期的启动子。这些发现在酵母和植物中得到了验证，包括一种分析植物中必需基因条件性功能丧失的新方法。我们的研究结果支持一种模型，其中 TPL 对转录激活机制的预组装成核，以便在抑制解除后促进转录的快速发生。