Mapping Active RNA Polymerases in Proliferating and Quiescent Fission Yeast Cells Using Precision Run-On Sequencing.

The development of next-generation sequencing (NGS) approaches to investigate the functioning of RNA polymerases has led to groundbreaking advances in the field of transcriptional regulation. One powerful method, Precision nuclear Run-On sequencing (PRO-seq), maps the locations of RNA polymerase active sites genome-wide at high resolution. PRO-seq provides a snapshot of strand-specific transcriptional activity and does not rely on immunoprecipitation of the polymerase of interest. Notably, this technique has been utilized to investigate the control of the RNA polymerase II transcription cycle in a variety of model systems. However, the initially published PRO-seq method required significant amounts of starting sample and was technically challenging, both of which were deterrents for its broader use. Recently, an improved and simplified version called qPRO-seq that reduced the length of the experiment and the quantity of necessary input sample was developed for human and Drosophila cell lines. Here we provide an updated, step-by-step protocol in which we have validated and optimized qPRO-seq for the fission yeast Schizosaccharomyces pombe. Importantly, we have implemented this method for assessing RNA polymerase activity in nutrient-limiting conditions, for both proliferating and nitrogen-depleted quiescent cells.