(105c) A Coherent Feedforward Loop Implemented at a Single Promoter

The coherent feedforward loop represents a prevalent network motif in transcriptional regulatory networks that can introduce delays and memory in the response of gene expression to external signals. Here we describe the development of a modular ?gene oscilloscope' in budding yeast that allows us to precisely measure the dynamics of transcription. Using this tool, we show that a single promoter is capable of generating the same behavior of a 3-gene coherent feedforward loop. We analyze our results in the context of a simplified 3-state model and suggest the delay and memory arises from an altered chromatin state of the promoter. An interesting outcome of this behavior is the ability of some promoters to filter high-frequency signals. Finally, we suggest promoter designs that might lead to pulse-like responses associated with incoherent feedforward loops.