Revisiting the model for coactivator recruitment: Med15 can select its target sites independent of promoter-bound transcription factors
Activation domains (ADs) within transcription factors (TFs) induce gene expression by recruiting coactivators to specific regulatory regions. Within the prevailing model, TF-coactivator recruitment is independent of DNA binding, which is consistent with direct AD-coactivator interactions seen outside cells. However, this independence was not yet tested within the genomic context. Here, we targeted two Med15-interacting ADs to hundreds of budding yeast promoters through fusions with multiple DNA binding domains (DBDs), gradually controlling their abundances using libraries of synthetic promoters. Genomic profiling revealed that AD identity influences DNA binding locations and that transcription induction and Med15 recruitment are restricted to a subset of DBD-bound promoters displaying flexible expression, multiple-TFs binding, and fuzzy nucleosome architecture. Further, when fused to a DBD, Med15 redirected binding towards promoters of fuzzy nucleosomes, overcoming DBD-based preferences. Our results demonstrate that ADs and their recruited coactivators posses an inherent preference for genomic localization and, therefore, define the subset of induced promoters. Overall design: ChEC-Seq experiments at OD600 of 0.4, all of the samples except one have at least duplicates. 30 second MNase activation. The experiments with calibration control (see description here - ARO80-MNase addition) ARO80 tf with fused MNase was added to the culture as a 10% ratio calculated by the respective OD600.