title: TbPIF1, a Trypanosoma brucei mitochondrial DNA helicase, is essential for kinetoplast minicircle replication.
abstract: Kinetoplast DNA, the trypanosome mitochondrial genome, is a network of interlocked DNA rings including several thousand minicircles and a few dozen maxicircles. Minicircles replicate after release from the network, and their progeny reattach. Remarkably, trypanosomes have six mitochondrial DNA helicases related to yeast PIF1 helicase. Here we report that one of the six, TbPIF1, functions in minicircle replication. RNA interference (RNAi) of TbPIF1 causes a growth defect and kinetoplast DNA loss. Minicircle replication intermediates decrease during RNAi, and there is an accumulation of multiply interlocked, covalently closed minicircle dimers (fraction U). In studying the significance of fraction U, we found that this species also accumulates during RNAi of mitochondrial topoisomerase II. These data indicate that one function of TbPIF1 is an involvement, together with topoisomerase II, in the segregation of minicircle progeny.
authors.affiliation: Department of Biological Chemistry, Johns Hopkins Medical School, Baltimore, Maryland 21205, USA.
authors.forename: Beiyu
authors.initials: B
authors.lastname: Liu
authors.forename: Gokben
authors.initials: G
authors.lastname: Yildirir
authors.forename: Jianyang
authors.initials: J
authors.lastname: Wang
authors.forename: Gökhan
authors.initials: G
authors.lastname: Tolun
authors.forename: Jack D
authors.initials: JD
authors.lastname: Griffith
authors.forename: Paul T
authors.initials: PT
authors.lastname: Englund
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D004261:DNA Replication; D004250:DNA Topoisomerases, Type II / Q000235:genetics / Q000378:metabolism; D018105:DNA, Kinetoplast / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000201:enzymology / Q000235:genetics; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014346:Trypanosoma brucei brucei / Q000201:enzymology / Q000235:genetics
chemical_list: D018105:DNA, Kinetoplast; D024101:Mitochondrial Proteins; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; D000255:Adenosine Triphosphate; D004265:DNA Helicases; D004250:DNA Topoisomerases, Type II