TAILIEUCHUNG - Báo cáo khoa học: A truncated form of DNA topoisomerase IIb associates with the mtDNA genome in mammalian mitochondria

Despite the likely requirement for a DNA topoisomerase II activity during synthesis of mitochondrial DNA in mam-mals, this activity has been very difficult to identify II activity conclusively demonstrated to be mitochondrial in origin is that of a type II activity found associated with the mitochondrial, kineto-plast DNAnetwork in trypanosomatid protozoa [Melendy, T., Sheline, C., and Ray, . (1988)Cell55, 1083–1088; Shapiro, ., andEnglund, . (1989). , 4173–4178] | Eur. J. Biochem. 270 4173-4186 2003 FEBS 2003 doi A truncated form of DNA topoisomerase IIP associates with the mtDNA genome in mammalian mitochondria Robert L. Low1 Shayla Orton1 and David B. Friedman2 1 Department of Pathology and 2Department of Cellular and Structural Biology University of Colorado Health Sciences Center Denver CO UsA Despite the likely requirement for a DNA topoisomerase II activity during synthesis of mitochondrial DNA in mammals this activity has been very difficult to identify convincingly. The only DNAIopoísomerase II activity conclusively demonstrated to be mitochondrial in origin is that of a type II activity found associated with the mitochondrial kineto-plast DNA network in trypanosomatid protozoa Melendy T. Sheline C. and Ray . 1988 Cell 55 1083-1088 Shapiro . Klein . and Englund . 1989 J. Biol. Chem. 264 4173-4178 . In the peesent ttady we report the discovery of a type DNA topoisomerase II activity in bovine mitochondria. Idmtihdl moogg mtDNA eepihca r e proteins recovered from complexes of mtDNA and protein the DNA topoisomerase relaxes a negatively supercoiled DNA template in vitro in a reaction that requires Mg2 and ATP. The relaxation activity is inhibited by etoposide and other inhibitors of eucaryotic type II enzymes. The DNA topoisomerase II copurifies with mitochondria and directly associates with mtDNA as indicated by sensitivity of some mtDNA circles in the isolated complex of mtDNA and protein to cleavage by etoposide. The purified act í VÍ ty can be assigned to a w 150-kDa protein which is recognized by a polyclonal antibody made against the trypanosomal mitochondrial topo II enzyme. Ml ass spectrometry performed on peptides prepared from the w 150-kDa protein demonstrate that this bovine mitochondrial activity is a truncated version of DNA topoisomerase IIP one of two DNA topoisomerase II activities known to exist in mammalian nuclei. Keywords mitochondrial DNA topoisomerase .

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