Identification of the transcription initiation site reveals a novel transcript structure for Plasmodium falciparum maebl.

Strict regulation of gene expression is critical for the development of the malaria parasite within multiple host cell types. However, much remains unexplored regarding gene regulation in Plasmodium falciparum with only a few components of the gene regulation machinery identified thus far. Better characterization of transcript structures with precise mapping of transcript ends will greatly aid in the search of conserved regulatory sequences in the genome. Transcript analysis of maebl, a member of the ebl gene family, in P. falciparum intra-erythrocytic stages has revealed a unique transcript structure for maebl. The 5'-untranslated region of maebl transcript is exceptionally long (>2 kb) with a small multi-exon open reading frame, annotated as a putative mitochondrial ATP synthase (PF11_0485) in the Plasmodium database. Northern blot hybridizations and RT-PCR analysis confirmed a bicistronic message for maebl along with PF11_0485. We further identified the minimal maebl promoter to be upstream of PF11_0485 by using transient chloramphenicol acetyl transferase (CAT) reporter assays. The occurrence of a bicistronic mRNA in Plasmodium is both novel and unusual for a lower eukaryote and adds on to the complexity of gene regulation in malaria parasites.