Multiple mitochondrial DNA polymerases in Trypanosoma brucei.
Kinetoplast DNA (kDNA), the unusual mitochondrial DNA of Trypanosoma brucei, is a network containing thousands of catenated circles. Database searching for a kDNA replicative polymerase (pol) revealed no mitochondrial pol gamma homolog. Instead, we identified four proteins (TbPOLIA, IB, IC, and ID) related to bacterial pol I. Remarkably, all four localized to the mitochondrion. TbPOLIB and TbPOLIC localized beside the kDNA where replication occurs, and their knockdown by RNA interference caused kDNA network shrinkage. Furthermore, silencing of TbPOLIC caused loss of both minicircles and maxicircles and accumulation of minicircle replication intermediates, consistent with a role in replication. While typical mitochondria contain one DNA polymerase, pol gamma, trypanosome mitochondria contain five such enzymes, including the previously characterized pol beta.
Klingbeil
Michele M
MM
Department of Biological Chemistry, Johns Hopkins Medical School, Baltimore, Maryland 21205, USA.
Motyka
Shawn A
SA
Englund
Paul T
PT
D000595:Amino Acid Sequence; D000818:Animals; D018105:DNA, Kinetoplast; D004259:DNA-Directed DNA Polymerase / Q000737:chemistry / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012330:RNA, Double-Stranded / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D014346:Trypanosoma brucei brucei / Q000201:enzymology* / Q000235:genetics
D018105:DNA, Kinetoplast; D012330:RNA, Double-Stranded; D012333:RNA, Messenger; D004259:DNA-Directed DNA Polymerase