Poster abstracts
Poster number 56 submitted by Antonia Duran
Fragment based lead discovery for alternative BET family targeting
Antonia D. Duran (OSU Department of Chemistry and Biochemistry), David Aceti (University of Wisconsin Madison), Mark P. Foster (OSU Department of Chemistry and Biochemistry)
Abstract:
Bromodomain and extraterminal domain (BET) family proteins contain two tandem bromodomains (BDs) that bind acetylated histone lysines, and an extraterminal (ET) domain that recruits chromatin-modifying proteins. The BET family includes Brd2, Brd3, Brd4, and BrdT, with Brd4 being the most well-studied. Brd4 activates transcription of the proto-oncogene MYC, and is a target for anti-cancer therapeutic development. Known Brd4-targeting inhibitors target the bromodomains and inhibit Brd4 activity by blocking binding to acetylated lysines. These inhibitors (BETis) have had some success in clinical trials, but success has been limited in part due to off-target toxicities that restrict treatment dose. Although BETis are designed to selectively bind BDs of BET proteins, all BDs share a conserved interaction with acetylated lysine, and binding with other BDs does occur. While bromodomains are widespread in human proteins, the ET domain is unique to BET family proteins. As the ET domain is essential for Brd4’s overall activity, we hypothesize that targeting the ET domain with small molecules may provide for higher specificity while maintaining the desired inhibitory effect. To test this hypothesis, we are developing a cell-permeable ligand of the ET domain using fragment based lead discovery (FBLD). Primary screening of a 500 compound fragment library against the Brd4 ET domain by 1D 1H-NMR resulted in 9 strong hits. Location of hit binding on the ET domain will be determined by 2D 1H-15N-HSQC titrations. Hits that bind the known ET domain protein interaction site will be further optimized into a lead-like ligand and tested for selective BET family inhibition. This work was supported by NIH grant R21AI124463 (MPF) and made use of the National Magnetic Resonance Facility at Madison, which is supported by NIH grant P41GM103399 (NIGMS).
Keywords: fragment screening, drug lead discovery, Brd4