Isoxazole‐Derived Amino Acids are Bromodomain‐Binding Acetyl‐Lysine Mimics: Incorporation into Histone H4 Peptides and Histone H3

Angelina R Sekirnik (Née Measures),Stuart J Conway,Timothy P C Rooney,Katie R Lewendon,David S Hewings,Natalie H Theodoulou,Lukass Jursins,Laura E Jennings,Tom D Heightman

doi:10.1002/ange.201602908

Angelina R Sekirnik (Née Measures), Stuart J Conway + Show 7 more

Open Access

https://doi.org/10.1002/ange.201602908

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Abstract

AbstractA range of isoxazole‐containing amino acids was synthesized that displaced acetyl‐lysine‐containing peptides from the BAZ2A, BRD4(1), and BRD9 bromodomains. Three of these amino acids were incorporated into a histone H4‐mimicking peptide and their affinity for BRD4(1) was assessed. Affinities of the isoxazole‐containing peptides are comparable to those of a hyperacetylated histone H4‐mimicking cognate peptide, and demonstrated a dependence on the position at which the unnatural residue was incorporated. An isoxazole‐based alkylating agent was developed to selectively alkylate cysteine residues in situ. Selective monoalkylation of a histone H4‐mimicking peptide, containing a lysine to cysteine residue substitution (K12C), resulted in acetyl‐lysine mimic incorporation, with high affinity for the BRD4 bromodomain. The same technology was used to alkylate a K18C mutant of histone H3.

Highlights

A range of isoxazole-containing amino acids was synthesized that displaced acetyl-lysine-containing peptides from the BAZ2A, BRD4(1), and BRD9 bromodomains
Acetylated lysine (KAc) residues are found throughout the cellular environment,[3,4,5] it is the role of this post-translational modification (PTM) in chromatin function which has garnered most recent interest.[6]
During the development of ligands for the bromodomain and extra-terminal domain (BET) family of bromodomaincontaining proteins (BCPs), we identified the 3,5-dimethylisoxazole (DMI) moiety as an effective KAc mimic.[29,30,31]

Summary

Introduction

Abstract: A range of isoxazole-containing amino acids was synthesized that displaced acetyl-lysine-containing peptides from the BAZ2A, BRD4(1), and BRD9 bromodomains. Three of these amino acids were incorporated into a histone H4mimicking peptide and their affinity for BRD4(1) was assessed. Affinities of the isoxazole-containing peptides are comparable to those of a hyperacetylated histone H4-mimicking cognate peptide, and demonstrated a dependence on the position at which the unnatural residue was incorporated.

Results

Conclusion