Bromodomain Proteins as Targets for anti-Leishmanial Drug Discovery

The Leishmaniases, caused by species of the kinetoplastid parasite Leishmania, are diseases associated with immune dysfunction, with millions of people at risk in the poorest countries of the world. Clinical symptoms range from the disfiguring skin lesions of cutaneous leishmaniasis, to the often fatal visceral leishmaniasis. The principal drugs used to treat visceral leishmaniasis suffer from serious drawbacks. The development of new therapies for treating leishmaniasis is an international priority.
Reversible histone acetylation by lysine acetyl transferases and histone deacetylases is an important mechanism of epigenetic control in eukaryotes. Following histone acetylation, nucleosomes, which hitherto form tightly packed chromatin, adopt a more open conformation that allows access to the transcription machinery. Transcription is often further regulated by the binding of bromodomain (BRD)-containing proteins. BRDs have as their core a four-helix bundle from which two prominent loops protrude to form an acetyl lysine binding site (Figure 1). BRDs bind to specific acetylated lysines on histones and can subsequently mediate the recruitment of transcriptional enhancers.
Parasites such as Leishmania spp. have complex life-cycles involving different developmental stages in more than one host. They are known to use epigenetic mechanisms, including lysine acetylation, to fine tune gene expression as they adapt to different hosts or conditions. The presence of multiple bromodomain containing proteins in the genome of the parasites suggests these proteins play a role in 'reading' lysine acetylation signals. In collaborative work with the pharmaceutical company GSK, the group of JCM has systematically knocked out/down genes encoding BRD-containing proteins. The results indicate that a subset of these proteins are essential for parasite proliferation and therefore represent targets for anti-leishmanial drug discovery.
Here, the student will use combinations of techniques of Structural Biology. This will include DNA manipulation and cloning to generate bacterial and/or insect cell lines over-producing recombinant proteins. These will be purified using advanced chromatographic techniques and the purified proteins used to support inhibitor-binding experiments using biophysical techniques including isothermal titration calorimetry, surface plasmon resonance and NMR spectroscopy. A key goal will be protein crystallisation and protein structure determination. We are well set up for protein crystallography with robotics devices for crystallisation and for crystal testing. We have monthly access to the synchrotron radiation source at DIAMOND for 3D data collection.
The student will be involved in a collaborative project and work closely with the molecular cell biologists performing the gene knock-outs in the parasites. There will be opportunities to interact with partners in the extended collaborative network including researchers in Brazil and industry.