Grants and Contributions:

Grant or Award spanning more than one fiscal year. (2017-2018 to 2018-2019)

The proposed research program focuses on the study of mechanisms controlling the flow of information from RNA to protein. We use a unicellular intracellular parasite, called Toxoplasma gondii, as our study model . This parasite is an eukaryotic organism that can infect any nucleated mammalian organism. Therefore, it offers an ideal system for the study of molecular/cell biological processes as well as intracellular parasitism. While in human, T. gondii is found in two forms, called tachyzoites and bradyzoites for their fast and slow growth, respectively. Tachyzoites are the cause of acute infection, as they can rapidly multiply inside a host cell, until the host cell ruptures. Tachyzoites can also convert to bradyzoites, which persist for the host’s lifetime and can cause latent infection.

To identify key molecular events critical to T. gondii’ s ability to establish an acute and latent infection, we pay close attention to the interactions between mRNA and its interacting proteins in T. gondii during the formation of mR NA-ribo n ucleo p rotein (mRNP) complexes. The assembly of mRNP complexes into mRNP granules is conserved in T. gondii and all eukaryotic organisms, and has significant implications in the control of mRNA translation (protein synthesis) and degradation. The assembly and disassembly of mRNP granules allows the reciprocal movement of mRNAs among different functional mRNP granules to provide a swift response to developmental and environmental cues.

Our working hypotheses are (i) that mRNP granule assembly allows for the parasites to ready themselves to withstand less-favourable growth environments, and (ii) that mRNP granule disassembly provides necessary mRNAs and protein products to re-establish infection. Here we set out to answer the following: How do mRNP granule assembly and disassembly affect T. gondii infectivity? What is the significance of each participating partner of mRNP granules in controlling protein synthesis?

We will use transgenic parasite strains expressing a fluorescent version of mRNP-residential proteins, named poly(A) binding protein (TgPABP) and RNA helicase (TgHoDI), for the study. The kinetics of assembly and disassembly will be monitored using a fluorescence microscope. The size and numbers of fluorescent mRNP granules will be quantitatively analyzed and correlated to the parasite's ability to attach, invade, and replicate in human cells. We will identify and characterize critical components of functional mRNP complexes and/or granules responsible for the regulation of protein synthesis. This fundamental research will bring forth invaluable information crucial to a better understanding of the molecular mechanisms of translational regulation, and host-parasite interactions.