Biology subjects

Cao, A.-M.

Publications and source records attributed to Cao, A.-M..

2 recordsLinked to original sources

bioRxiv2021

Single molecule analysis reveals positive allosteric modulators are required to stabilize the active state of a metabotropic glutamate receptor

Much hope in drug development comes from the discovery of positive allosteric modulators (PAM) that display target subtype selectivity, and act by increasing agonist potency and efficacy. How such compounds can allosterically influence agonist action remains unclear. Metabotropic glutamate receptors (mGlu) are G protein-coupled receptors that represent promising targets for brain diseases, and for which PAMs acting in the transmembrane domain have been developed. Here, we explore the effect of a PAM on the structural dynamics of mGlu2 in optimized detergent micelles using single molecule FRET at submillisecond timescales. We show that glutamate only partially stabilizes the extracellular domains in the active state. Full activation is only observed in the presence of a PAM or the Gi protein. Our results provide important insights on the role of allosteric modulators in mGlu activation, by stabilizing the active state of a receptor that is otherwise rapidly oscillating between active and inactive states.

biophysics↗

bioRxiv2019

The mechanistic basis for chromatin invasion and remodeling by the yeast pioneer transcription factor Rap1

Pioneer transcription factors (pTFs) bind to target sites within compact chromatin initiating chromatin remodeling and controlling the recruitment of downstream factors. The mechanisms by which pTFs overcome the chromatin barrier are not well understood. Here we reveal, using single-molecule fluorescence approaches, how the yeast transcription factor Rap1 invades and remodels chromatin. Using a reconstituted chromatin system replicating yeast promoter architecture we demonstrate that Rap1 can bind nucleosomal DNA within a chromatin fiber, but with shortened dwell times compared to naked DNA. Moreover, we show that Rap1 binding opens chromatin fiber structure by inhibiting nucleosome-nucleosome contacts. Finally, we reveal that Rap1 collaborates with the chromatin remodeler RSC to destabilize promoter nucleosomes, paving the way to form long-lived bound states on now exposed DNA. Together, our results provide a mechanistic view of how Rap1 gains access and opens chromatin, thereby establishing an active promoter architecture and controlling gene expression.

biophysics↗