title: Trypanosomes have six mitochondrial DNA helicases with one controlling kinetoplast maxicircle replication.
abstract: Kinetoplast DNA (kDNA), the trypanosome mitochondrial DNA, contains thousands of minicircles and dozens of maxicircles interlocked in a giant network. Remarkably, Trypanosoma brucei's genome encodes 8 PIF1-like helicases, 6 of which are mitochondrial. We now show that TbPIF2 is essential for maxicircle replication. Maxicircle abundance is controlled by TbPIF2 level, as RNAi of this helicase caused maxicircle loss, and its overexpression caused a 3- to 6-fold increase in maxicircle abundance. This regulation of maxicircle level is mediated by the TbHslVU protease. Previous experiments demonstrated that RNAi knockdown of TbHslVU dramatically increased abundance of minicircles and maxicircles, presumably because a positive regulator of their synthesis escaped proteolysis and allowed synthesis to continue. Here, we found that TbPIF2 level increases following RNAi of the protease. Therefore, this helicase is a TbHslVU substrate and an example of a positive regulator, thus providing a molecular mechanism for controlling maxicircle replication.
authors: Department of Biological Chemistry, Johns Hopkins Medical School, Baltimore, MD 21205, USA.
authors: Beiyu
authors: B
authors: Liu
authors: Jianyang
authors: J
authors: Wang
authors: Nurit
authors: N
authors: Yaffe
authors: Megan E
authors: ME
authors: Lindsay
authors: Zhixing
authors: Z
authors: Zhao
authors: Aviad
authors: A
authors: Zick
authors: Joseph
authors: J
authors: Shlomai
authors: Paul T
authors: PT
authors: Englund
mesh_terms: D000818:Animals; D004265:DNA Helicases / Q000235:genetics / Q000378:metabolism*; D004261:DNA Replication; D018105:DNA, Kinetoplast / Q000096:biosynthesis*; D004272:DNA, Mitochondrial / Q000096:biosynthesis*; D016054:DNA, Protozoan / Q000096:biosynthesis*; D005786:Gene Expression Regulation; D009154:Mutation; D010447:Peptide Hydrolases / Q000378:metabolism; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*; D034622:RNA Interference; D013997:Time Factors; D014162:Transfection; D014346:Trypanosoma brucei brucei / Q000201:enzymology / Q000235:genetics* / Q000254:growth & development
chemical_list: D018105:DNA, Kinetoplast; D004272:DNA, Mitochondrial; D016054:DNA, Protozoan; D015800:Protozoan Proteins; D010447:Peptide Hydrolases; D004265:DNA Helicases