Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham 720 20th Street South, Birmingham, AL 35294, USA.
Genes (Basel). 2021 Mar 12;12(3):413. doi: 10.3390/genes12030413.
RNA polymerases (Pols) I, II, and III collectively synthesize most of the RNA in a eukaryotic cell. Transcription by Pols I, II, and III is regulated by hundreds of trans-acting factors. One such protein, Spt4, has been previously identified as a transcription factor that influences both Pols I and II. Spt4 forms a complex with Spt5, described as the Spt4/5 complex (or DSIF in mammalian cells). This complex has been shown previously to directly interact with Pol I and potentially affect transcription elongation. The previous literature identified defects in transcription by Pol I when was deleted, but the necessary tools to characterize the mechanism of this effect were not available at the time. Here, we use a technique called Native Elongating Transcript Sequencing (NET-seq) to probe for the global occupancy of Pol I in wild-type (WT) and (yeast) cells at single nucleotide resolution in vivo. Analysis of NET-seq data reveals that Spt4 promotes Pol I processivity and enhances transcription elongation through regions of the ribosomal DNA that are particularly G-rich. These data suggest that Spt4/5 may directly affect transcription elongation by Pol I in vivo.
RNA 聚合酶（Pols）I、II 和 III 共同合成真核细胞中的大部分 RNA。Pols I、II 和 III 的转录受数百种反式作用因子的调节。Spt4 是一种先前被鉴定为影响 Pols I 和 II 的转录因子的蛋白质。Spt4 与 Spt5 形成复合物，称为 Spt4/5 复合物（或哺乳动物细胞中的 DSIF）。先前的研究表明，该复合物直接与 Pol I 相互作用，并可能影响转录延伸。以前的文献表明，当 缺失时，Pol I 的转录会出现缺陷，但当时没有可用的工具来描述这种影响的机制。在这里，我们使用一种称为天然延伸转录测序（NET-seq）的技术，以单核苷酸分辨率在体内探测野生型（WT）和 （酵母）细胞中 Pol I 的整体占据情况。NET-seq 数据分析表明，Spt4 促进 Pol I 的延伸能力，并通过富含 G 的核糖体 DNA 区域增强转录延伸。这些数据表明，Spt4/5 可能直接影响体内 Pol I 的转录延伸。
