The fungal natural product azaphilone-9 binds to HuR and inhibits HuR-RNA interaction in vitro

  • PLoS One. 2017 Apr 17;12(4):e0175471. doi: 10.1371/journal.pone.0175471.
Kawaljit Kaur  1 ,  Xiaoqing Wu  1 ,  James K Fields  1 ,  David K Johnson  2 ,  Lan Lan  1 ,  Miranda Pratt  1 ,  Amber D Somoza  3 ,  Clay C C Wang  3  4 ,  John Karanicolas  1  5 ,  Berl R Oakley  1 ,  Liang Xu  1 ,  Roberto N De Guzman  1
Affiliations
  • 1. Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas, United States of America.
  • 2. Molecular Graphics and Modeling Laboratory and the Computational Chemical Biology Core, University of Kansas, Lawrence, Kansas, United States of America.
  • 3. Department of Chemistry, University of Southern California, Los Angeles, California, United States of America.
  • 4. Department of Pharmacology and Pharmaceutical Sciences, School of Pharmacy, University of Southern California, Los Angeles, California United States of America.
  • 5. Center for Computational Biology, University of Kansas, Lawrence, Kansas, United States of America.
PMID: 28414767 DOI: 10.1371/journal.pone.0175471
Abstract

The RNA-binding protein Hu antigen R (HuR) binds to AU-rich elements (ARE) in the 3'-untranslated region (UTR) of target mRNAs. The HuR-ARE interactions stabilize many oncogenic mRNAs that play important roles in tumorigenesis. Thus, small molecules that interfere with the HuR-ARE interaction could potentially inhibit Cancer cell growth and progression. Using a fluorescence polarization (FP) competition assay, we identified the compound azaphilone-9 (AZA-9) derived from the Fungal natural product asperbenzaldehyde, binds to HuR and inhibits HuR-ARE interaction (IC50 ~1.2 μM). Results from surface plasmon resonance (SPR) verified the direct binding of AZA-9 to HuR. NMR methods mapped the RNA-binding interface of HuR and identified the involvement of critical RNA-binding residues in binding of AZA-9. Computational docking was then used to propose a likely binding site for AZA-9 in the RNA-binding cleft of HuR. Our results show that AZA-9 blocks key RNA-binding residues of HuR and disrupts HuR-RNA interactions in vitro. This knowledge is needed in developing more potent AZA-9 derivatives that could lead to new Cancer therapy.

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