Argonaute2 attenuates active transcription by limiting RNA Polymerase II elongation in Drosophila melanogaster [ChIPseq-PolII-S2]

Increasing lines of evidence support that Argonaute2 (AGO2) harbors several nuclear functions in metazoa. In particular, Drosophila AGO2 modulates transcription of developmentally regulated genes; however, the molecular mechanisms behind AGO2 recruitment into chromatin and its function in transcription have not been deeply explored. In this study, we show that Drosophila AGO2 chromatin association depends on active transcription. In order to gain insight into how AGO2 controls transcription, we performed differential ChIP-seq analysis for RNA Polymerase II (Pol II) upon depletion of AGO2. Interestingly, we find specific accumulation of the elongating but not initiating form of Pol II after AGO2 knockdown, suggesting that AGO2 impairs transcription elongation. Finally, AGO2 also affects Negative Elongation Factor (CDK9) chromatin association but not the Cyclin Dependent Kinase 9 (CDK9). Altogether, these results provide key insights into the molecular role of AGO2 in attenuating elongation of certain actively transcribed genes. ChIP-seq of RNA PolII S2 (serine 2 phosphorylated) in Drosophila melanogaster Kc167 cells in mock treatment, Ago2 knockdown, and LaminB knockdown. Two replicates per condition, with paired inputs.

越来越多的研究证据表明，Argonaute2（AGO2）在后生动物（Metazoa）中具备多种核功能。具体而言，果蝇AGO2可调控发育相关基因的转录，但AGO2被招募至染色质的分子机制及其在转录过程中的功能尚未得到深入探究。本研究证实，果蝇AGO2的染色质结合依赖于活跃的转录过程。为深入解析AGO2调控转录的具体方式，我们对AGO2敲低后的RNA聚合酶II（Pol II）开展了差异染色质免疫共沉淀测序（ChIP-seq）分析。有趣的是，我们发现AGO2敲低后，Pol II的延伸型而非起始型亚型出现特异性富集，这提示AGO2会抑制转录延伸过程。此外，AGO2还会影响负延伸因子（CDK9）的染色质结合能力，但对细胞周期蛋白依赖性激酶9（CDK9）本身并无此类作用。综上，本研究结果为AGO2在抑制部分活跃转录基因的延伸过程中的分子功能提供了关键见解。本数据集涵盖黑腹果蝇（Drosophila melanogaster）Kc167细胞在空白对照处理、AGO2敲低以及LaminB敲低三种条件下，丝氨酸2磷酸化的RNA聚合酶II S2（RNA PolII S2）的染色质免疫共沉淀测序数据；每个处理条件设置两个生物学重复，并配有配对的输入对照样本。