Catalytic-dependent and independent functions of the histone acetyltransferase CBP promote pioneer factor-mediated zygotic genome activation [RNA-Seq]

Immediately after fertilization the genome is transcriptionally quiescent. Maternally encoded pioneer transcription factors reprogram the chromatin state and facilitate the transcription of the zygotic genome. In Drosophila, transcription is initiated by the pioneer factor Zelda. While Zelda-occupied sites are enriched with histone acetylation, a post-translational mark associated with active cis-regulatory regions, the functional relationship between Zelda and histone acetylation in zygotic genome activation remained unclear. We show that Zelda-mediated recruitment of the histone acetyltransferase CBP is essential for zygotic transcription and embryonic development. CBP catalytic activity is necessary for release of RNA Polymerase II (Pol II) into transcription elongation. However, CBP largely activates zygotic transcription independent of acetylation through Pol II recruitment. Neither acetylation nor CBP are required for the pioneering function of Zelda. Our data suggest that pioneer factor-mediated recruitment of CBP is a conserved mechanism required to activate zygotic transcription but that this role is separable from the function of pioneer factors in restructuring chromatin accessibility. Overall design: This data set contains bulk RNA-seq on CBPHAT embryos 2h15min -3 hours AEL (nuclear cycle 14). To assay the catalytic function of CBP we used a catalytic mutant CBPHAT (F2161A). The mutant protein is exclusively loaded in embryos with the help of Dominant Female Sterile technique to produce germline clones, compared to a control line (w1118), both genotypes were analyzed in three replicates.

受精完成后即刻，基因组处于转录静默状态。由母源编码的先驱转录因子（pioneer transcription factor）重塑染色质状态，并促进合子基因组的转录。在果蝇（Drosophila）中，合子转录由先驱转录因子Zelda启动。尽管Zelda结合位点富集有组蛋白乙酰化（histone acetylation）——一种与活跃顺式调控区域相关的翻译后修饰标记，但Zelda与组蛋白乙酰化在合子基因组激活中的功能关联仍不明确。本研究证实，Zelda介导的组蛋白乙酰转移酶（histone acetyltransferase, HAT）CBP招募过程，对合子转录与胚胎发育至关重要。CBP的催化活性对于RNA聚合酶II（RNA Polymerase II, Pol II）释放进入转录延伸阶段是必需的。然而，CBP主要通过招募Pol II来激活合子转录，这一过程不依赖于乙酰化修饰。Zelda的先驱功能既不需要乙酰化修饰，也不需要CBP。本研究数据表明，先驱转录因子介导的CBP招募是激活合子转录所必需的保守机制，但该功能与先驱转录因子重塑染色质可及性的功能相互独立。实验设计概述：本数据集包含CBPHAT胚胎在产卵后2小时15分至3小时（核周期14）的批量RNA测序（bulk RNA-seq）数据。为检测CBP的催化功能，本研究使用了催化突变体CBPHAT（F2161A）。借助显性雌性不育（Dominant Female Sterile）技术构建生殖系克隆，使突变蛋白仅在胚胎中表达；以对照品系w1118为参照，对两种基因型均设置3次生物学重复。