Personally I am not interested in the kinetics of promoter activation, I just care about the underlying sequence motifs. However, I found the methods used in this paper utterly exciting and very well worthy of our time to read. I'll just go through the basic idea; for more details consult the original paper.
The authors set out to study the kinetics of promoter occupancy in endogenous promoters. To do so, they use the CUP1 promoter in yeast which is found in 10 tandem repeats. Adding three GFPs to Ace1p (the cu-inducible TF which binds CUP1) makes it possible to actually visualize the occupancy under a microscope (see the figure below with and without cu induction).
Upon making this set-up, they use laser beams to bleach the transcription factors occupying the promoter (yellow arrows above). Then they measure the time that is needed for the fluorescence to reach the initial intensity. This graph (below) depends on the retention time of the activator on the promoter and in this case the intensity reaches maximum in a matter of minutes.
As I said, I won't go into details, but using these tools the authors make the case that this activator goes through a fast (~1 min) and a slow (~15-90 min) cycle. They show that (using ChIP-chip and RT-PCR) the slow cycling regulates the quantity of the RNA produced; whereas, the fast cycle is actually in charge of transcription initiation.
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