Tuning gene expression for parasite resilience and persistence

Sebastian Lourido (Whitehead Institute for Biomedical Research, MIT, USA)

15:00 - 15:30 Monday 13 April Morning

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Abstract

The apicomplexan parasite Toxoplasma gondii survives by navigating constantly shifting environments—crossing cellular barriers, remodeling host defenses, and ultimately establishing long-term reservoirs within tissues. Achieving this balance between replication and persistence requires the precise tuning of gene-expression across multiple regulatory layers through largely unexplored mechanisms. Our recent work reveals the coordinated action of chromatin remodeling, translational control, and post-transcriptional metabolic regulation as it shapes T. gondii resilience and persistence. Parasites have streamlined the canonical SWI/SNF machinery to a pair of divergent remodelers whose mutually exclusive ATPases choreograph stage- and cell-cycle–specific transcription, coupling DNA accessibility to the timing demands of parasite division and developmental transitions. Downstream of these chromatin dynamics, extraordinarily long 5′ UTRs and pervasive upstream initiation sites modulate protein synthesis in unexpected ways that differ from canonical models. Translation is also tuned by additional factors that contribute to T. gondii gene-expression plasticity. A stress-responsive RNA-binding protein, BFD2, plays a key role in chronic differentiation by mediating translation of the master regulator BFD1, helping lock parasites into the persistent state through positive feedback. At later stages, when parasites experience metabolic tension within the crowded cyst environment, a newly discovered RNA-binding factor, TgPRO, adjusts expression of pathways supporting redox balance and iron-sulfur cluster assembly, shaping cyst fitness. Together, these findings expose an integrated regulatory architecture that enables parasites to sense their environment, remodel gene expression, and persist for the lifetime of their host.

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