GSE159633
RTF1 and SPT6 stimulate transcription elongation by two distinct mechanisms
We have previously shown that the RNA polymerase II (Pol II)-DSIF complex associates with the PAF1 complex (PAF), RTF1 and SPT6 to form an activated elongation complex in vitro. Here we investigate the mechanisms that these factors use to stimulate Pol II elongation in vivo. We combine rapid factor depletion from human cells with genome-wide analyses of changes in RNA synthesis and occupancy with engaged Pol II. Whereas depletion of PAF subunits has little effect on transcription in vivo, depletion of RTF1 or SPT6 strongly compromises RNA synthesis, albeit in fundamentally different ways. RTF1 depletion decreases Pol II velocity, whereas SPT6 depletion impairs Pol II progression through nucleosomes. These results show that distinct transcription elongation factors stimulate Pol II velocity and Pol II progression through chromatin in vivo. Our results also provide evidence for two distinct barriers to elongation at the beginning of genes, the promoter-proximal pause site and the +1 nucleosome. Overall design: 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.