Kinetoplast DNA (kDNA) is the mitochondrial DNA of trypanosomes, parasitic protozoa that cause major human disease. The major subject of our study is Trypanosoma brucei that causes African sleeping sickness, although related parasites with kDNA cause Chagas disease and Leishmaniasis. kDNA is an unusual structure, consisting of DNA circles that are interlocked into a giant network that has a structure like that of medieval chain mail. The network contains several thousand minicircles and a few dozen maxicircles. Our major interest is the replication of kDNA. Major steps in this process include the sequential release of monomeric minicircles from the network by a topoisomerase to form free minicircles, replication of the free minicircles via theta structures, reattachment of the progeny minicircles to the network, and ultimately segregation of the double-size network into two daughter networks. One major emphasis of this proposal, presented in Aim 1, is to study proteins involved in kDNA replication. Because of the unusual structure of kDNA and because it is essential for parasite viability, these proteins could be targets for anti- trypanosome chemotherapy. Another approach, presented in Aim 2, is to study the regulation of kDNA replication. Unlike mitochondrial DNAs in higher eukaryotes, kDNA replicates during only part of the cell cycle, nearly concurrent with the nuclear S phase. We will try to understand what controls the timing. Finally, in Aim 3, we will study the molecular basis of segregation of the progeny networks that are formed during kDNA replication.

Public Health Relevance

Our research focuses on the synthesis of an unusual trypanosome mitochondrial DNA, called kinetoplast DNA, that consists of a giant network of interlocked DNA rings. Kinetoplast DNA is required for viability of parasites causing important tropical diseases such as sleeping sickness, Chagas disease, and Leishmaniasis. Since there is nothing resembling kinetoplast DNA in human cells, its synthesis may be a useful target for selective chemotherapy.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
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Pathogenic Eukaryotes Study Section (PTHE)
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Mcgugan, Glen C
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Johns Hopkins University
Schools of Medicine
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Wang, Jianyang; Pappas-Brown, Valeria; Englund, Paul T et al. (2014) TbKAP6, a mitochondrial HMG box-containing protein in Trypanosoma brucei, is the first trypanosomatid kinetoplast-associated protein essential for kinetoplast DNA replication and maintenance. Eukaryot Cell 13:919-32
Povelones, Megan L; Tiengwe, Calvin; Gluenz, Eva et al. (2013) Mitochondrial shape and function in trypanosomes requires the outer membrane protein, TbLOK1. Mol Microbiol 87:713-29
Wang, Jianyang; Englund, Paul T; Jensen, Robert E (2012) TbPIF8, a Trypanosoma brucei protein related to the yeast Pif1 helicase, is essential for cell viability and mitochondrial genome maintenance. Mol Microbiol 83:471-85
Clayton, April M; Guler, Jennifer L; Povelones, Megan L et al. (2011) Depletion of mitochondrial acyl carrier protein in bloodstream-form Trypanosoma brucei causes a kinetoplast segregation defect. Eukaryot Cell 10:286-92
Gluenz, Eva; Povelones, Megan L; Englund, Paul T et al. (2011) The kinetoplast duplication cycle in Trypanosoma brucei is orchestrated by cytoskeleton-mediated cell morphogenesis. Mol Cell Biol 31:1012-21
Liu, Beiyu; Yildirir, Gokben; Wang, Jianyang et al. (2010) TbPIF1, a Trypanosoma brucei mitochondrial DNA helicase, is essential for kinetoplast minicircle replication. J Biol Chem 285:7056-66
Liu, Beiyu; Wang, Jianyang; Yildirir, Gokben et al. (2009) TbPIF5 is a Trypanosoma brucei mitochondrial DNA helicase involved in processing of minicircle Okazaki fragments. PLoS Pathog 5:e1000589
Liu, Beiyu; Wang, Jianyang; Yaffe, Nurit et al. (2009) Trypanosomes have six mitochondrial DNA helicases with one controlling kinetoplast maxicircle replication. Mol Cell 35:490-501
Jensen, Robert E; Simpson, Larry; Englund, Paul T (2008) What happens when Trypanosoma brucei leaves Africa. Trends Parasitol 24:428-31
Lindsay, Megan E; Gluenz, Eva; Gull, Keith et al. (2008) A new function of Trypanosoma brucei mitochondrial topoisomerase II is to maintain kinetoplast DNA network topology. Mol Microbiol 70:1465-76

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