Investigating the mechanism of heterogeneous protein accumulation among the nuclei of a Plasmodium falciparum schizont

Abstract text

Plasmodium falciparum proliferates through schizogony in the clinically relevant blood stage of infection. During schizogony, the nuclei multiply several times and the parasite develops into a multinucleated stage before cellularization occurs and daughter cells are released. To facilitate rapid parasite proliferation, the nuclei multiply asynchronously despite residing in the same cytoplasm. Moreover, the DNA replication fork protein P. falciparum PCNA1 accumulates only in those nuclei that replicate their DNA. However, the molecular mechanisms that enable heterogeneous nuclear accumulation of P. falciparum PCNA1 and thus asynchronous nuclear multiplication are not yet understood. To investigate this phenomenon, we used super-resolution live-cell microscopy. Our data suggest that P. falciparum PCNA1 initially accumulates close to the centrosome before relocating towards the nuclear periphery. This may indicate that the progression of the S-phase follows a conserved intranuclear pattern and that PCNA1 accumulation in subnuclear compartments underlies a specific spatiotemporal control. To elucidate this regulation, we are using mutagenesis and synthetic approaches to analyse how different protein motifs of P. falciparum PCNA1 contribute to its heterogeneous accumulation. Our data suggest that several amino acids play an important role. This work also identified a poorly conserved P. falciparum PCNA1 lysine-rich motif that was sufficient to accumulate GFP at the centrosomes. Building on these findings, we are now testing the behaviour of additional mutants and profiling the interactomes of wild-type and mutant P. falciparum PCNA1. Together, this will grant further molecular insight into the underlying mechanism of heterogeneous protein accumulation among P. falciparum nuclei.