Norstictic Acid Is a Selective Allosteric Transcriptional Regulator

J Am Chem Soc. 2021 Jun 30;143(25):9297-9302. doi: 10.1021/jacs.1c03258. Epub 2021 Jun 17.


Inhibitors of transcriptional protein-protein interactions (PPIs) have high value both as tools and for therapeutic applications. The PPI network mediated by the transcriptional coactivator Med25, for example, regulates stress-response and motility pathways, and dysregulation of the PPI networks contributes to oncogenesis and metastasis. The canonical transcription factor binding sites within Med25 are large (∼900 Å2) and have little topology, and thus, they do not present an array of attractive small-molecule binding sites for inhibitor discovery. Here we demonstrate that the depsidone natural product norstictic acid functions through an alternative binding site to block Med25-transcriptional activator PPIs in vitro and in cell culture. Norstictic acid targets a binding site comprising a highly dynamic loop flanking one canonical binding surface, and in doing so, it both orthosterically and allosterically alters Med25-driven transcription in a patient-derived model of triple-negative breast cancer. These results highlight the potential of Med25 as a therapeutic target as well as the inhibitor discovery opportunities presented by structurally dynamic loops within otherwise challenging proteins.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Allosteric Regulation
  • Cell Line, Tumor
  • DNA-Binding Proteins / metabolism
  • Humans
  • Lactones / pharmacology*
  • Mediator Complex / chemistry
  • Mediator Complex / metabolism*
  • Molecular Dynamics Simulation
  • Protein Binding / drug effects*
  • Protein Domains
  • Salicylates / pharmacology*
  • Transcription Factors / metabolism
  • Transcription, Genetic / drug effects*


  • DNA-Binding Proteins
  • ETV5 protein, human
  • Lactones
  • MED25 protein, human
  • Mediator Complex
  • Salicylates
  • Transcription Factors
  • norstictic acid