Hypothetical bromodomain-containing protein 5 is required for the growth of Toxoplasma gondii.

Bromodomain (BRD) is a highly conserved structural module domain, found in various proteins, including chromatin-related proteins, nucleus acetyltransferases, and transcription-associated proteins. Toxoplasma gondii, a zoonotic protozoan, encodes at least 12 predicted BRD-containing proteins (BDPs). Here, we investigated the subcellular location and regulatory role of a hypothetical protein BDP that we named TgBDP5. The BRD of TgBDP5 did not contain the conserved Asn and Tyr residues required for acetyl-lysine recognition. TgBDP5 localized in the nucleus of the parasite and remained unchanged during parasite replication. Conditional ablation of TgBDP5 through an auxin-inducible degron-based knockdown strategy caused a growth defect in parasite replication. Depletion of TgBDP5 led to changes in the expression level of 179 genes, suggesting it as an important target for drugs acting against T. gondii.