Figure 7. A working model for WC-1-dependent recruitment of SWI/SNF to initiate frq transcription.

In the night before frq transcription starts, NucB is in a repressive state occluding the C box as fostered by chromatin remodelers that may include CHD-1. When active WC-1/WC-2 begin to bind at the C box, an event roughly coincident with CSW binding, SWI/SNF is recruited and it helps to fully remodel the C box to an active state, removing NucB, and also beginning to bring about the DNA looping (curved gray line) that is essential to bring the WCC transcriptional activation domains to the transcription start site (TSS) for stable recruitment of general transcription factors (GTFs). For acute light-induction of frq, an action not requiring SWI/SNF, WCC binds directly to the PLRE rather than the C box and recruits unknown remodelers to drive frq transcription at levels much higher than in the dark.