The FACT (FAcilitates Chromatin Transactions) complex influences transcription initiation and enables passage of RNA polymerase (pol) II through gene body nucleosomes during elongation. In the budding yeast, ~280 non-coding RNA genes highly transcribed in vivo by pol III are found in the nucleosome-free regions bordered by positioned nucleosomes. The downstream nucleosome dynamics was found to regulate transcription via controlling the gene terminator accessibility and hence, terminator-dependent pol III recycling. As opposed to the enrichment at the 5'-ends of pol II-transcribed genes, our genome-wide mapping found transcription-dependent enrichment of the FACT subunit Spt16 near the 3'-end of all pol III-transcribed genes. Spt16 physically associates with the pol III transcription complex and shows gene-specific occupancy levels on the individual genes. On the non-tRNA pol III-transcribed genes, Spt16 facilitates transcription by reducing the nucleosome occupany on the gene body. On the tRNA genes, it maintains the position of the nucleosome at the 3' gene-end and affects transcription in gene-specific manner. Under nutritional stress, Spt16 enrichment is abolished in the gene downstream region of all pol III-transcribed genes and reciprocally changed on the induced or repressed pol II-transcribed ESR genes. Under the heat and replicative stress, its occupancy on the pol III-transcribed genes increases significantly. Our results show that Spt16 elicits a differential, gene-specific and stress-responsive dynamics, which provides a novel stress-sensor mechanism of regulating transcription against external stress. By primarily influencing the nucleosomal organization, FACT links the downstream nucleosome dynamics to transcription and environmental stress on the pol III-transcribed genes.

中文翻译：

---

酵母FACT复合物的转录依赖性富集影响核小体对RNA聚合酶III转录基因的动力学

FACT (FAcilitates Chromatin Transactions) 复合物影响转录起始并使 RNA 聚合酶 (pol) II 在延伸过程中通过基因体核小体。在出芽酵母中，在与定位的核小体相邻的无核小体区域中发现了约 280 个由 pol III 在体内高度转录的非编码 RNA 基因。发现下游核小体动力学通过控制基因终止子的可及性来调节转录，因此，终止子依赖的 pol III 再循环。与 pol II 转录基因 5' 端的富集相反，我们的全基因组图谱发现 FACT 亚基 Spt16 在所有 pol III 转录基因的 3' 端附近的转录依赖性富集。Spt16 在物理上与 pol III 转录复合物相关联，并显示单个基因上的基因特异性占用水平。在非 tRNA pol III 转录的基因上，Spt16 通过减少基因体上的核小体占据来促进转录。在 tRNA 基因上，它保持核小体在 3' 基因末端的位置，并以基因特异性方式影响转录。在营养压力下，Spt16 富集在所有 pol III 转录基因的基因下游区域被取消，并在诱导或抑制的 pol II 转录 ESR 基因上相互改变。在热和复制胁迫下，它对 pol III 转录基因的占有率显着增加。我们的研究结果表明，Spt16 引发了差异化、基因特异性和压力反应动力学，它提供了一种新的压力传感器机制来调节转录以对抗外部压力。通过主要影响核小体组织，FACT 将下游核小体动力学与 pol III 转录基因的转录和环境压力联系起来。