Translational Repression in Malaria Sporozoites

Malaria is a mosquito-borne infectious disease of humans and other animals. It is caused by the parasitic protozoan, Plasmodium. Sporozoites, the infectious form of malaria parasites, are quiescent when they remain in the salivary glands of the Anopheles mosquito until transmission into a mammalian host. Metamorphosis of the dormant sporozoite to its active form in the liver stage requires transcriptional and translational regulations. Here, we summarize recent advances in the translational repression of gene expression in the malaria sporozoite. In sporozoites, many mRNAs that are required for liver stage development are translationally repressed. Phosphorylation of eukaryotic Initiation Factor 2 alpha (eIF2 alpha) leads to a global translational repression in sporozoites. The eIF2 alpha kinase, known as Upregulated in Infectious Sporozoite 1 (UIS1), is dominant in the sporozoite. The eIF2 alpha phosphatase, UIS2, is translationally repressed by the Pumilio protein Puf2. This translational repression is alleviated when sporozoites are delivered into the mammalian host.