Nuclear factor (NF)-κB controls the transcriptional response to inflammatory signals by translocating into the nucleus, but we lack a single-cell characterization of the resulting transcription dynamics. Here we show that upon tumor necrosis factor (TNF)-α transcription of NF-κB target genes is heterogeneous in individual cells but results in an average nascent transcription profile that is prompt (i.e., occurs almost immediately) and sharp (i.e., increases and decreases rapidly) compared with NF-κB nuclear localization. Using an NF-κB-controlled MS2 reporter we show that the single-cell nascent transcription is more heterogeneous than NF-κB translocation dynamics, with a fraction of synchronized “first responders” that shape the average transcriptional profile and are more prone to respond to multiple TNF-α stimulations. A mathematical model combining NF-κB-mediated gene activation and a gene refractory state is able to reproduce these features. Our work shows how the expression of target genes induced by transcriptional activators can be heterogeneous across single cells and yet time resolved on average.

核因子（NF）-κB通过转移到细胞核中来控制对炎症信号的转录反应，但是我们缺乏对所得转录动力学的单细胞表征。在这里，我们显示在肿瘤坏死因子（TNF）-α的作用下，NF-κB靶基因的转录在单个细胞中是异质的，但是会导致平均新生的转录谱，即迅速（即，几乎立即发生）和急剧（即，增加和与NF-κB核定位相比迅速下降）。使用由NF-κB控制的MS2报告基因，我们显示单细胞新生转录比NF-κB易位动力学更加异质，部分同步的“第一反应者”塑造了平均转录谱，并且更易于响应多种TNF-α刺激。结合NF-κB介导的基因激活和基因难治性状态的数学模型能够再现这些特征。我们的工作表明，转录激活因子诱导的靶基因表达如何在单个细胞之间是异质的，而平均时间却无法解析。