Identification and characterization of a Plasmodium falciparum RNA polymerase gene with similarity to mitochondrial RNA polymerases

Nearly all mitochondrial RNA polymerase genes identified to date are encode d in the nucleus and have similarities to T3 and T7 bacteriophage RNA polym erases. Some chloroplast genes are also transcribed by T3/T7 phage-like RNA polymerases, raising the possibility that the apicomplexan parasites, whic h have both a mitochondrion and a plastid. might have two such genes. As pa rr of an investigation of Plasmodium falciparum organelle transcription, we initiated a search for T3;T7 bacteriophage-like RNA polymerase genes. We e mployed degenerate primers based on highly conserved plant, animal and fung al mitochondrial RNA polymerase sequences to amplify corresponding P. falci parum sequences by polymerase chain reaction (PCR). Less well-conserved fla nking sequences were obtained by inverse PCR. The resulting sequence predic ts a 1503 amino acid open reading frame with similarity to other T3/T7 phag e-like RNA polymerases. Essential amino acids that hav been identified in T 7 mutant analyses are conserved in the P. falciparum RNA polymerase gene. C omparison of the sequence with preliminary data from the P. falciparum geno me sequencing project revealed strain heterogeneity within two regions of t he gene. The amino-terminal predicted amino acid sequence of the RNA polyme rase gene has similarities to mitochondrial targeting sequences. Taken toge ther. these points suggest that we have identified the P. falciparum mitoch ondrial RNA polymerase gene. (C) 2001 Elsevier Science B.V. All rights rese rved.