Poster Presentation Lorne Infection and Immunity 2014

Dual targeted tRNA synthetases: decoding Plasmodium alternative translation initiation. (#162)

Katherine E Jackson 1 , James S Pham 1 , Stacey M Allen 1 , Christopher D Goodman 1 , Geoffrey I McFadden 1 , Stuart A Ralph 1
  1. University of Melbourne, Parkville, VIC, Australia

Plasmodium falciparum has three translationally active compartments: the cytosol, the mitochondrion and a relic plastid called the apicoplast. The nuclear genome encodes 36 distinct copies of canonical aminoacyl-tRNA synthetases, insufficient to supply a unique enzyme for each amino acid in all three compartments. We have investigated the subcellular localisation of four tRNA synthetases (AlaRS, CysRS, GlyRS and ThrRS) and we show each of these enzymes are dually localised to the P. falciparum cytosol and the apicoplast. Alternative translation initiation drives alternative cellular targeting in a number of organisms and has been implicated in the regulation of stage-specific protein expression. Translation initiation variants have been implicated in dual-targeting of tRNA synthetases in other organisms and have led us to investigate the potential mechanism behind dual-targeted tRNA synthetases in P. falciparum. Here we utilise in vitro translation assays to determine the regulatory sequences necessary for alternative translation initiation. Additionally, we have generated parasite lines with multiple fluorescence reporters to dissect alternative translation initiation dynamics throughout the P. falciparum life cycle. With an unusually high number of putative translation initiation sites it seems likely that the parasite may exploit this as a potential way to increase protein diversity through initiation at alternative start sites.