Toxoplasma gondii Chromodomain Protein 1 Binds to Heterochromatin and Colocalises with Centromeres and Telomeres at the Nuclear Periphery

Background Apicomplexan parasites are responsible for some of the most deadly parasitic diseases afflicting humans, including malaria and toxoplasmosis. These obligate intracellular parasites exhibit a complex life cycle and a coordinated cell cycle-dependant expression program. Their cell division is a coordinated multistep process. How this complex mechanism is organised remains poorly understood. Methods and Findings In this study, we provide evidence for a link between heterochromatin, cell division and the compartmentalisation of the nucleus in Toxoplasma gondii . We characterised a T. gondii chromodomain containing protein (named TgChromo1) that specifically binds to heterochromatin. Using ChIP-on-chip on a genome-wide scale, we report TgChromo1 enrichment at the peri-centromeric chromatin. In addition, we demonstrate that TgChromo1 is cell-cycle regulated and co-localised with markers of the centrocone. Through the loci-specific FISH technique for T. gondii , we confirmed that TgChromo1 occupies the same nuclear localisation as the peri-centromeric sequences. Conclusion We propose that TgChromo1 may play a role in the sequestration of chromosomes at the nuclear periphery and in the process of T. gondii cell division.