Pressing Pause The pausing of RNA polymerase II (Pol II) near promoters is an important and distinct regulatory step in the process of transcribing DNA into RNA. Although protein factors and DNA elements involved in pausing have been identified, the post-initiation events that lead to pausing are poorly understood. Kwak et al. (p. 950 ) present an approach, termed PRO-seq, for monitoring the position of actively transcribing RNA polymerase with single-nucleotide precision. The approach was used to explore the mechanism of promoter proximal pausing and showed that precise positioning between core promoter elements and the pause site is critical. The findings show how the promoter dictates transcriptional pausing and detects the preferential localization of active transcription complexes within the genome.