Spatially coherent diffusion of human RNA Pol II depends on transcriptional state rather than chromatin motion

Abstract Gene transcription by RNA polymerase II (RNAP II) is a tightly regulated process in the genomic, temporal, and spatial context. Transcriptionally active genes often spatially cluster at RNA Pol II foci, called transcription factories, causing long-range interactions between distal sites of the genome. Recently, we have shown that chromatin exhibits spatially long-range coherently moving regions over the entire nucleus, and transcription enhances this long-range correlated DNA movement. Yet, it remains unclear how the mobility of RNA Pol II molecules is affected by transcription regulation and whether this response depends on the coordinated chromatin movement. We applied our Dense Flow reConstruction and Correlation method to analyze nucleus-wide coherent movements of RNA Pol II in living human cancer cells. We quantify the spatial correlation length of RNA Pol II in the context of DNA motion. We observe a spatially coherent movement of RNA Pol II molecules over ~1 μm, considerably less than for DNA, suggesting that spatially coherent RNA Pol II motion does not solely result from the DNA motion. In contrast to DNA, inducing transcription in quiescent cells decreased the coherent motion of RNA Pol II, while the inhibition of transcription elongation by using DRB slightly increased coherent RNA Pol II motion. The spatially coherent movement of RNA Pol II domains is affected by the transcriptional state and largely independent of the underlying chromatin domains. Our study reveals the nucleus-wide interplay between chromatin and RNA Pol II in the dynamic regulation of chromatin organization.