Fig. 1. The export of TEEGR in the host cell nucleus.

The gene TGME49_239010 encoding TEEGR was originally identified in silico together with GRA16⁴, GRA24⁵ and TgIST⁶,⁷ as strong parasite candidate genes with attributes to both target the parasite secretory pathway and to reach the host cell nuclei. a, TEEGR is a highly disordered 80 kDa protein (predicted disorder score > 0.5) that carries a signal peptide, a putative nuclear localization sequence (NLS) and multiple repeated domains (R1, R2 and R3) whose repeat number and distribution have evolved through coccidian subclasses and among T. gondii lineages. Tg: Toxoplasma gondii, Nc: Neospora caninum, Hh: Hammondia hammondia. b, HAFlag (HF)-tagged TEEGR (in red) in Pru∆ku80 extracellular parasites is contained in cytoplasmic organelles distinct from the apical micronemes (MIC2, in green) and rhoptries (Toxofilin, in green), and partially co-localizing with the dense granule protein GRA7 (in green). Cells were co-stained with Hoechst DNA-specific dye (in blue). Scale bars, 1 μm. c, Time course of TEEGR secretion and export to the host cell nucleus. Human Foreskin Fibroblasts (HFF) were infected with a Pru∆ku80 TEEGR-HF and stained with anti-HA antibodies (red). Scale bars, 10 μm. d, in situ subcellular localization of TEEGR chimeric proteins (in red) in HFF infected with parasites expressing endogenously HF-tagged TEEGR truncated proteins (TEEGR∆SER and TEEGR∆R3) or TEEGR^Nter-R3 expressed under the control of a TUB8 promoter. Scale bars, 10 μm. All data are representative of 3 independent biological experiments.