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There is now a CONTENT FREEZE for Mercury while we switch to a new platform. It began on Friday, March 10 at 6pm and will end on Wednesday, March 15 at noon. No new content can be created during this time, but all material in the system as of the beginning of the freeze will be migrated to the new platform, including users and groups. Functionally the new site is identical to the old one. webteam@gatech.edu
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Danae Schulz, Ph.D.
Assistant Professor
Department of Biology
Harvey Mudd College
Abstract
Trypanosoma brucei, the causative agent of African sleeping sickness, is transmitted to its mammalian host by the tsetse. In the fly, the parasite’s surface is covered with invariant procyclin, while in the mammal it resides extracellularly in its bloodstream form (BF) and is densely covered with highly immunogenic Variant Surface Glycoprotein (VSG). In the BF, the parasite varies this surface VSG, using a repertoire of ~2500 distinct VSG genes. Recent reports in mammalian systems point to a role for histone acetyl-lysine recognizing bromodomain proteins in the maintenance of stem cell fate, leading us to hypothesize that bromodomain proteins may maintain the BF cell fate in trypanosomes. Using small-molecule inhibitors and genetic mutants for individual bromodomain proteins, we performed RNA-seq experiments that revealed changes in the transcriptome similar to those seen in cells differentiating from the BF to the insect stage. This was recapitulated at the protein level by the appearance of insect-stage proteins on the cell surface. Furthermore, bromodomain inhibition disrupts two major bloodstream-specific immune evasion mechanisms. Thus, our studies reveal a role for trypanosome bromodomain proteins in maintaining lifecycle stage identity and immune evasion. Importantly, bromodomain inhibition leads to a decrease in virulence in a mouse model of infection, establishing these proteins as therapeutic drug targets for trypanosomiasis. Our 1.25Å resolution crystal structure of a trypanosome bromodomain in complex with a known acetyl-lysine mimetic reveals a novel binding mode of the inhibitor, which serves as a promising starting point for rational drug design. Current efforts in the lab are aimed at optimizing the Cut and Run technique to further characterize bromodomain localization during the transition from bloodstream to insect stage cells. We have also set up reporter systems to be able to carry out high-throughput screens for small molecule inhibitors that initiate a transition from bloodstream stages to the insect stages, and recently used them to screen a library of FDA approved drugs.
Host: Joshua Weitz, Ph.D.
