Characterisation of a disordered nuclear effector protein that interacts with FOXO1 in Theileria-transformed cells

Abstract text

Theileria are tick-borne apicomplexan parasites that infect bovine leukocytes and cause Tropical Theileriosis. Within a few days of infection, parasitized leukocytes acquire a transformed phenotype comprising uncontrolled proliferation, resistance to apoptosis, immortality and increased invasiveness. This phenotype depends strictly on the presence of a viable parasite. RNA sequencing allowed us to identify extensive gene expression changes in primary macrophages following infection with Theileria. These include an upregulation of genes involved in DNA replication, cell cycle and translation, and a downregulation of genes involved in adhesion and innate immune response. To try to understand how Theileria modulates host gene expression networks, we used a comparative bioinformatics approach to identify Theileria-encoded effector proteins that are exported into the host nucleus. To facilitate this we performed Oxford Nanopore and Illumina whole genome sequencing on seven T. annulata clones isolated from different geographical regions. We analysed features such as selective pressure (dN/dS ratio) and protein disorderedness to identify and validate novel Theileria effector proteins. One of the identified proteins, TaC12_008960, is highly enriched in the host nucleus where it binds to the transcription factor Forkhead box protein O1 (FOXO1). FOXO transcription factors regulate many cellular processes including nutrient metabolism, DNA damage response, autophagy, cell cycle progression and oxidative stress response. FOXO1 expression is increased following infection, and immunofluorescence and western blot analysis confirmed that FOXO1 is localized in the nucleus of infected cells. We are exploring the functional significance of this interaction and testing what effect TaC12_008960 nuclear expression has on FOXO1 activity.