The Transition of Poised RNA Polymerase II to an Actively Elongating State Is a “Complex” Affair

Figure 2

Mutating SPN1, which results in loss of Spn1 and constitutive recruitment of Swi/Snf to the promoter, does not bypass the requirement for SAGA or Mediator. CYC1 transcript levels were analyzed before and two or four hours after induction in ethanol using an S1 nuclease protection assay [23] with RNA isolated from wild-type, ada1Δ or med20Δ strains. Each strain harbors either a wild-type (WT) or mutant (MT) form of SPN1. Similar results were obtained for other SAGA and Mediator deletion strains, including gcn5Δ, spt7Δ, spt8Δ, spt20Δ, med5Δ, med15Δ, and med18Δ (data not shown).