Alternative trans-splicing of the Trypanosoma cruzi LYT1 gene transcript results in compartmental and functional switch for the encoded protein.

Trypanosoma cruzi has a complex life cycle that includes infective and non-infective stages in distinct hosts. Control of gene expression by the parasite must adjust to rather diverse circumstances. Through stage-regulated, alternative trans-splicing of the primary transcript, the T. cruzi LYT1 gene generates two protein products differing in the presence or absence of 28 amino acids at their amino end. We find that the shorter protein, kLYT1, is located at two spots in the mitochondrial kinetoflagellar zone and its expression reverts the 'accelerated stage development' phenotype of the LYT1-null mutant. The larger product, mLYT1, localizes on the plasma membrane. The signal for membrane localization presents characteristics of a type II anchor including the possibility of cleavage. Expression of mLYT1 reverts the 'loss of virulence' phenotype associated to diminished haemolytic activity at acid pH, but stage development still progresses at an accelerated rate. This compartmentalization switch of LYT1 results in two surprisingly different functions: haemolytic activity at acid pH for mLYT1, and a putative involvement in mitochondrial metabolism for kLYT1. We conclude that alternative trans-splicing plays an important role in stage-regulated control of gene expression in trypanosomatids.