(R3779) Histone Recognition by the BDP1 Bromodomain of Plasmodium falciparum

Saleh Alkrimi (Albany College of Pharmacy and Health Sciences (ACPHS))| Samuel Boyson (Albany College of Pharmacy and Health Sciences (ACPHS))| Margaret Phillips (Albany College of Pharmacy and Health Sciences (ACPHS))| Marina Juan (Albany College of Pharmacy and Health Sciences (ACPHS))| Karen Glass (Albany College of Pharmacy and Health Sciences (ACPHS))

Bromodomains are evolutionarily conserved protein modules that specifically recognize acetylated lysine residues on histone tails of the nucleosome. During the red-blood-cell-stage of infection with Plasmodium falciparum, the parasite undergoes repeated rounds of replication, egress, and invasion. Erythrocyte invasion involves specific interactions between host cell receptors and parasite ligands and coordinated expression of genes specific to this step of the life cycle. A parasite-specific protein known as bromodomain protein 1 (PfBDP1) binds to chromatin at the transcriptional start sites of invasion-related genes and directly controls their expression. Conditional PfBDP1 knockdown causes a dramatic defect in parasite invasion and growth, and results in transcriptional down-regulation of multiple invasion-related genes at a time point critical for invasion. Conversely, PfBDP1 overexpression enhances expression of these same invasion-related genes. PfBDP1 has been shown to interact with acetylated histone H3 and a second bromodomain protein, PfBDP2, suggesting a potential mechanism for gene recognition and control. Since PfBDP1 critically coordinates expression of invasion genes, targeting PfBDP1 could be an invaluable tool in mitigating malaria infections. The domain architecture of PfBDP1 includes a single C-terminal bromodomain and several ankyrin repeats. PfBDP1 is thought to act by tethering a transcriptional activator complex to acetylated histone H3 to control genes required for parasite invasion. We hypothesized that the bromodomain is crucial for this function of PfBDP1 via recognition of acetylated lysine modifications. We carried out several histone binding assays to identify novel histone interactions the of PfBDP1 bromodomain. We also utilized a combination of structural biology and biophysical approaches to identify amino acid residues critical for ligand coordination. The result of this study will provide molecular details about the recognition of acetylated histone ligands by the PfBDP1 bromodomain and shed light on how this domain recruits the PfBDP1-PfBDP2 complex to chromatin. Importantly, these results may improve the development of new therapeutics to treat malaria