Figure 2. Model for Gdown1 function. The diagram illustrates the transcription cycles performed by RNAP II (blue) and RNAP II(G) (orange). As described in the text, both forms of polymerase can initiate and ultimately enter productive elongation. RNAP II(G) requires Mediator (not shown) for initiation. A major difference between the two cycles is that promoter proximal paused RNAP II is transient while paused RNAP II(G) is stable due to the ability of Gdown1 to block the termination activity of TTF2.