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.