Facile target validation in an animal model with intracellularly expressed monobodies

Nat Chem Biol. 2018 Sep;14(9):895-900. doi: 10.1038/s41589-018-0099-z. Epub 2018 Jul 16.


Rapidly determining the biological effect of perturbing a site within a potential drug target could guide drug discovery efforts, but it remains challenging. Here, we describe a facile target validation approach that exploits monobodies, small synthetic binding proteins that can be fully functionally expressed in cells. We developed a potent and selective monobody to WDR5, a core component of the mixed lineage leukemia (MLL) methyltransferase complex. The monobody bound to the MLL interaction site of WDR5, the same binding site for small-molecule inhibitors whose efficacy has been demonstrated in cells but not in animals. As a genetically encoded reagent, the monobody inhibited proliferation of an MLL-AF9 cell line in vitro, suppressed its leukemogenesis and conferred a survival benefit in an in vivo mouse leukemia model. The capacity of this approach to readily bridge biochemical, structural, cellular characterization and tests in animal models may accelerate discovery and validation of druggable sites.

Publication types

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

MeSH terms

  • Animals
  • Cell Line, Tumor
  • Cell Proliferation / drug effects
  • Disease Models, Animal
  • Homeodomain Proteins / antagonists & inhibitors*
  • Homeodomain Proteins / genetics
  • Intracellular Signaling Peptides and Proteins
  • Mice
  • Oligopeptides / chemistry
  • Oligopeptides / pharmacology*
  • Proteins / antagonists & inhibitors*
  • Proteins / metabolism
  • RNA, Messenger / antagonists & inhibitors
  • RNA, Messenger / genetics
  • Reproducibility of Results


  • Homeodomain Proteins
  • Intracellular Signaling Peptides and Proteins
  • MM-401
  • Oligopeptides
  • Proteins
  • RNA, Messenger
  • Wdr5 protein, mouse
  • homeobox protein HOXA9