Structure–function studies of Rgg binding to pheromones and target promoters reveal a model of transcription factor interplay
Glenn C. Capodagli, Kaitlyn M. Tylor, Jason T. Kaelber, Vasileios I. Petrou, Michael J. Federle, Matthew B. Neiditch
Abstract
Rgg3 in complex with their target DNA promoters. The physiological importance of observed Rgg-DNA interactions was dissected using in vivo genetic experiments and in vitro biochemical assays. Based on these structure-function studies, we present a revised unifying model of Rgg regulatory interplay. In contrast to existing models, where Rgg2 proteins are transcriptional activators and Rgg3 proteins are transcriptional repressors, we propose that both are capable of transcriptional activation. However, when Rgg proteins with different activation requirements compete for the same DNA promoters, those with more stringent activation requirements function as repressors by blocking promoter access of SHP-bound conformationally active Rgg proteins. While a similar gene expression regulatory scenario has not been previously described, in all likelihood it is not unique to streptococci.