IWS1 Stimulates Pol II Transcription Elongation In Vivo [mNET-seq]

Interacts with SPT6 1 (IWS1) has been implicated in various co-transcriptional processes, yet its direct role in RNA Polymerase (Pol) II transcription in vivo remains elusive. In this study, we utilized a rapid depletion system of IWS1 in human cells, followed by multi-omics analysis and biochemical assays, to elucidate its function. We show that IWS1 depletion results in a global decrease of RNA synthesis, but does not affect the chromatin recruitment of the histone methyltransferase SETD2. In vivo and in vitro analyses of nascent transcription and histone modifications revealed that the observed decrease in methylation is a secondary effect of the transcription defect caused by IWS1 depletion. Whereas these results show that IWS1 is essential for maintaining normal RNA Pol II elongation velocity in vivo, and that it can directly stimulate transcription. Samples for each condition were collected in biological duplicates. Cells were treated with dTAG7 for 1 hour, the corresponding control cells were treated for the same duration with the solvent only (DMSO) at the same vol/vol dilution.