Downsizing proto-oncogene cFos to short helix-constrained peptides that bind Jun

Daniel Baxter, Samuel R. Perry, Timothy A. Hill, W. Mei Kok, Nathan R. Zaccai, R. Leo Brady, David P. Fairlie*, Jody M. Mason

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)

9 Citations (Scopus)
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Abstract

The oncogenic transcription factor activator protein-1 (AP-1) is a DNA-binding protein that assembles through dimerization of Fos and Jun protein subunits, their leucine-rich helical sequences entwining into a coiled-coil structure. This study reports on downsizing the proto-oncogene cFos protein (380 residues) to shorter peptides (37-25 residues) modified with helix-inducing constraints to enhance binding to Jun. A crystal structure is reported for a 37-residue Fos-derived peptide (FosW) bound to Jun. This guided iterative downsizing of FosW to shorter peptide sequences that were constrained into stable water-soluble α-helices by connecting amino acid side chains to form cyclic pentapeptide components. Structural integrity in the presence and absence of Jun was assessed by circular dichroism spectroscopy, while the thermodynamics of binding to cFos was measured by isothermal titration calorimetry. A 25-residue constrained peptide, one-third shorter yet 25% more helical than the structurally characterized 37-residue Fos-derived peptide, retained 80% of the binding free energy as a result of preorganization in a Jun-binding helix conformation, with the entropy gain (TΔS = +3.2 kcal/mol) compensating for the enthalpy loss. Attaching a cell-penetrating peptide (TAT48-57) and a nuclear localization signal (SV40) promoted cell uptake, localization to the nucleus, and inhibition of the proliferation of two breast cancer cell lines.

Original languageEnglish
Pages (from-to)2051-2061
Number of pages11
JournalACS Chemical Biology
Volume12
Issue number8
Early online date21 Jun 2017
DOIs
Publication statusPublished - 18 Aug 2017

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    Baxter, D., Perry, S. R., Hill, T. A., Kok, W. M., Zaccai, N. R., Brady, R. L., Fairlie, D. P., & Mason, J. M. (2017). Downsizing proto-oncogene cFos to short helix-constrained peptides that bind Jun. ACS Chemical Biology, 12(8), 2051-2061. https://doi.org/10.1021/acschembio.7b00303