Translation initiation factor eIF1.2 orchestrates Toxoplasma gondii differentiation by regulating stage-specific gene expression

Toxoplasma gondii persists in humans by converting from actively replicating acute stage tachyzoites to slow-growing chronic stage bradyzoites. The molecular mechanisms that mediate T. gondii differentiation remain poorly understood. Through a chemical mutagenesis screen, we identified translation initiation factor eIF1.2 as being critical for T. gondii differentiation. The presence of an F97L mutation in eIF1.2 identified in the screen or the complete lack eIF1.2 (?eIF1.2) markedly impeded bradyzoite cyst formation in culture and in the brains of infected mice. ?eIF1.2 parasites were defective in the upregulation of bradyzoite differentiation regulators BFD1 and BFD2 during stress-induced differentiation. Conditional overexpression of BFD1 or BFD2 rescued differentiation in ?eIF1.2 parasites. We further show that eiF1.2 interacted with the yeast 40S ribosome and directed the scanning of a model 5' untranslated region. Together, our findings imply that eIF1.2 functions by regulating the translation of key differentiation factors necessary to establish T. gondii chronic infection. Overall design: expression changes at the transcriptional and translational levels compared between parental and eIF1.2 knockout Toxoplasma gondii tachyzoites and 48h alkaline stressed parasites