title: In vitro-reconstituted nucleoids can block mitochondrial DNA replication and transcription.
abstract: The mechanisms regulating the number of active copies of mtDNA are still unclear. A mammalian cell typically contains 1,000-10,000 copies of mtDNA, which are packaged into nucleoprotein complexes termed nucleoids. The main protein component of these structures is mitochondrial transcription factor A (TFAM). Here, we reconstitute nucleoid-like particles in vitro and demonstrate that small changes in TFAM levels dramatically impact the fraction of DNA molecules available for transcription and DNA replication. Compaction by TFAM is highly cooperative, and at physiological ratios of TFAM to DNA, there are large variations in compaction, from fully compacted nucleoids to naked DNA. In compacted nucleoids, TFAM forms stable protein filaments on DNA that block melting and prevent progression of the replication and transcription machineries. Based on our observations, we suggest that small variations in the TFAM-to-mtDNA ratio may be used to regulate mitochondrial gene transcription and DNA replication.
authors: Department of Physics and Astronomy and LaserLaB, VU University, De Boelelaan 1081, 1081 HV Amsterdam, the Netherlands.
authors: Géraldine
authors: G
authors: Farge
authors: Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden.
authors: Majda
authors: M
authors: Mehmedovic
authors: Department of Physics and Astronomy and LaserLaB, VU University, De Boelelaan 1081, 1081 HV Amsterdam, the Netherlands.
authors: Marian
authors: M
authors: Baclayon
authors: Institut Langevin, ESPCI ParisTech, 1, rue Jussieu, 75238 Paris Cedex 05, France.
authors: Siet M J L
authors: SM
authors: van den Wildenberg
authors: Department of Physics and Astronomy and LaserLaB, VU University, De Boelelaan 1081, 1081 HV Amsterdam, the Netherlands.
authors: Wouter H
authors: WH
authors: Roos
authors: Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden.
authors: Claes M
authors: CM
authors: Gustafsson
authors: Department of Physics and Astronomy and LaserLaB, VU University, De Boelelaan 1081, 1081 HV Amsterdam, the Netherlands. Electronic address: g.j.l.wuite@vu.nl.
authors: Gijs J L
authors: GJ
authors: Wuite
authors: Department of Medical Biochemistry and Cell Biology, University of Gothenburg, P.O. Box 440, SE-405 30 Gothenburg, Sweden. Electronic address: maria.falkenberg@medkem.gu.se.
authors: Maria
authors: M
authors: Falkenberg
mesh_terms: D004261:DNA Replication; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000235:genetics*; D004279:DNA, Viral / Q000737:chemistry / Q000235:genetics; D006801:Humans; D011485:Protein Binding; D055503:Protein Multimerization; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D004272:DNA, Mitochondrial; D004279:DNA, Viral; D014157:Transcription Factors