Abstract
The intracellular pathogen Toxoplasma gondii modifies a number of host cell processes. The mechanisms by which T. gondii alters host gene expression are incompletely understood. This study focuses on how the regulators of gene expression in human host cells respond to T. gondii 24 hours following infection to cause specific patterns of transcriptional dysregulation. The most striking finding was the altered landscape of transposase-accessible chromatin by infection. We found both gains and losses of loci of open chromatin enriched in proximity to transcriptionally altered genes. Both DNA sequence motif analysis at the loci changing chromatin accessibility and network analysis of the genes with transcription and regulatory changes implicate a central role for the AP-1 transcription factor. We validated the redistribution of AP-1 in the host genome using chromatin immunoprecipitation studies of the c-Fos component of AP-1. As infection with T. gondii is associated with the cell failing to progress through the cell cycle, all of the changes observed occur in the absence of cell division and within 24 hours, an insight into the dynamism of these transcriptional regulatory events. We conclude that T. gondii infection influences transcriptional regulation through transcription factor re-targeting to modify the cis-regulatory landscape of the host nucleus.
