The post-translational acetylation of lysine plays a crucial role in both cellular signaling as well as the regulation of transcription factors and other effector proteins. Identifying potent and selective inhibitors for histone acetyltransferases and histone deacetylases, the two enzymes known to control this lysine modification, has thus far proven to be challenging. An alternative attractive approach is to inhibit the machinery responsible for the recognition of this post-translational modification.

Bromodomains (BRDs), named after the Drosophila gene brahma from which the first BRD sequence motif was identified, are the protein-interaction modules that recognise acetylated lysine residues.¹ BRD-containing proteins play an intrinsic role in the conscription of certain complexes that facilitate cancer cell growth.² Therefore, BRD inhibitors serve as attractive molecules as novel cancer therapeutics. All known BRD modules contain a characteristic hydrophobic binding pocket that strongly recognises the acetylated lysine moiety which we proposed could be exploited in the design of a novel family of potent BRD inhibitors.

This poster will detail our work in identifying cyclic peptides possessing nanomolar affinity for a range of BRDs through the use of the RaPID mRNA display technology developed by Suga and co-workers.^3,4 The crystal structure of a lead peptide bound to different BRDs was obtained and used to rationally design a variety of analogues. These analogues were subsequently synthesised by Fmoc-solid-phase peptide synthesis and binding affinities determined by surface plasmon resonance (SPR).