Cohesin acts as a transcriptional gatekeeper by restraining pause-release to promote processive elongation

Cohesin organizes 3D chromatin architecture, including promoter-enhancer loops, yet its loss has surprisingly modest effects on steady-state gene expression. We address this paradox by demonstrating that cohesin acts at different stages of transcription in human cells. First, it promotes Pol II promoter recruitment by facilitating promoter-enhancer communication that maintains active promoter chromatin states. Second, it delays pause release by transiently associating with the transcriptional machinery during the pause-release transition. Kinetic modelling suggests that reduced Pol II recruitment and enhanced pause release have compensatory effects, contributing to minimal changes in steady-state gene expression across genes upon cohesin loss. In contrast, cohesin depletion impairs robust transcriptional induction in response to external stimuli. Moreover, cohesin ensures sufficient pausing duration as a quality-control-like step to promote elongation complex assembly and transcription processivity. Here, we show that cohesin regulates multiple transcriptional steps, offering mechanistic insight into cohesin-related diseases, including cancers and cohesinopathies.