ABSTRACT
A polymerase chain reaction (PCR)-based approach is being employed to study RNA transcripts in malarial parasites, a system that is not easily amenable to molecular studies. Our aim is to compare messages from different life cycle stages to determine whether regulatory information is encoded in the structure of plasmodial transcripts as a result of differential RNA processing. In particular, we have analyzed the structure of the message encoding the circumsporozoite (CS) protein of the murine malaria Plasmodium berghei, the immunodominant surface antigen of the infectious stage of the parasite. Our major findings are that a subset of the CS message utilizes multiple polyadenylation sites, that some processed CS transcripts are found in blood-stage parasites, and that the 5' untranslated region of the message is unusually long and has multiple start sites. Moreover, repetitive motifs that may represent enhancers or transcriptional binding sites are present upstream of the transcription unit. In addition, we describe details of the cDNA-directed PCR procedure that may be helpful to other parasitologists who work with small, unpurified biological samples.
