FACT orchestrates the interplay between chromatin structure and transcription [mNET-Seq]

Transcription by RNA polymerase II (RNA Pol II) depends on transcription factors and chromatin factors. Here we use rapid factor depletion and multiomics analysis to investigate how a histone chaperone, FAcilitates Chromatin Transcription (FACT), influence nascent transcription by RNA PolII in human cells. Depletion of a FACT subunit, SSRP1, led to rapid changes in chromatin structure and concomitantly strongly compromised RNA synthesis. FACT depletion led to a multilayered transcriptional defect, including loss of promoter proximal pausing, deregulated release into elongation and drop-off of RNA Pol II in promoter-distant gene regions. We combined these analyses with biochemical dissection of transcription of a chromatinized template to show that FACT supports both elongation and pausing of RNA Pol II. Our study also provides new evidence how the position of promoter proximal pausing is defined by the +1 nucleosome in human cells. Samples for each condition were collected in biological duplicates. Cells were treated with dTAG7 for 1 or 4 hours, the corresponding control cells were treated for the same duration with vehicle only (DMSO) at the same vol/vol dilution.