Fragment-Based Identification of Ligands for Bromodomain-Containing Factor 3 of Trypanosoma Cruzi

The Trypanosoma cruzi ( T. cruzi ) parasite is the cause of Chagas disease, a neglected disease endemic in South America. The life cycle of the T. cruzi parasite is complex and includes transitions between distinct life stages. This change in phenotype (without a change in genotype) could be controlled by epigenetic regulation, and might involve the bromodomain-containing factors 1-5 ( Tc BDF1-5). However, little is known about the function of the Tc BDF1-5. Here we describe a fragment-based approach to identify ligands for T. cruzi bromodomain-containing factor 3 ( Tc BDF3). We expressed a soluble construct of Tc BDF3 in E. coli , and used this to develop a range of biophysical assays for this protein. Fragment screening identified twelve compounds that bind to the Tc BDF3 bromodomain. Based on this screen, we developed functional ligands containing a fluorescence or 19 F reporter group, and a photo-crosslinking probe for Tc BDF3. These tools compounds will be invaluable in future studies on the function of Tc BDF3 and will provide insight into the biology of T. cruzi .