THE PLASMODIUM-FALCIPARUM 6 KB ELEMENT IS POLYCISTRONICALLY TRANSCRIBED

The Plasmodium falciparum 6 kb element encodes three protein coding ge nes and highly fragmented large and small subunit rRNAs; its gene cont ent makes it the probable mitochondrial genome. Many of the genes are encoded so close to each other that there is insufficient room for spe cific promoters upstream of each gene, RNase protection analysis of tw o rRNA fragments whose genes are adjacent provided evidence for a poly cistronic transcript containing sequences from both, as well as separa te small RNAs. To evaluate the possibility of further polycistronic tr anscription, several sets of oligonucleotide primers located in differ ent regions of the 6 kb element were employed to amplify cDNAs. These analyses have revealed the existence of 6 kb element transcripts as lo ng as 5.9 kb. Both mRNA and rRNA sequences are included on these putat ive precursor transcripts. Since these types of RNA are known to have different patterns of abundance changes during the erythrocytic portio n of the parasite lifecycle, RNA stability is presumably an important feature in regulating mitochondrial transcript abundance.