Roles of the RSC, ISW1, and CHD1 remodelers in Pol II initiation, elongation, and termination. RSC widens the promoter NDR by positioning the +1 and −1 nucleosomes farther apart to accommodate a complete barrier complex. CHD1 (short spacing) and ISW1 (longer spacing) compete to set nucleosome spacing on the gene using the +1 nucleosome as a reference. In rsc8 cells, nucleosomes shift toward the promoter but the spacing is the same as wild type; Pol II remains 3′ of the TTS. In isw1Δ chd1Δ cells, nucleosome spacing is disrupted, with the +2 nucleosome in particular being pushed against the +1 or +3 nucleosome. High cryptic initiation in these cells may result in collisions between transcribing cryptic antisense Pol II and promoter-initiated Pol II (elongation defect). Termination and/or dissociation in these cells may be faster.
