Authors

Discussion

A key element within the drug discovery pipeline for anti-leishmanial therapies is the identification and validation of new target proteins in Leishmania. Bromodomains (BDs) are epigenetic protein domains that recognise acetylated lysine residues in histone tails and regulate gene transcription through this interaction. BDs have been implicated in various diseases, which has opened up a field of BD inhibitor research. These efforts have been particularly rewarding with regard to cancer research, with several BD inhibitors entering clinical trials. These encouraging results provide rationale for the selective targeting of BDs in other diseases, such as leishmaniasis. Genetic target validation has identified Leishmania bromodomain factor 5 (BDF5) as essential for parasite survival. BDF5 contains two BDs, BDF5.1 and 5.2, and is hypothesised to play a role in global transcriptional regulation. Using recombinant protein production, BDF5 bromodomains have been expressed at York and screened by the pharmaceutical company GSK against small molecules and reactive compounds. This yielded numerous hit compounds which have been distributed to York for validation and characterisation in biophysical assays alongside various other compounds. Thermal shift assays (TSA), NMR and fluorescence polarization (FP) assays have been developed to validate these hits for on-target engagement using recombinant BDs. These assays have also been used to test binding of histone peptides to the Leishmania BDs, to investigate the acetylated histone sequence with which LdBDF5 interacts. Together, this work provides a platform for the validation and characterisation of hit compounds against the Leishmania BDs. With the support of genetic evidence of BDF protein essentiality, these approaches aim to establish these epigenetic proteins as targets for further anti-leishmanial drug discovery and development.