title: Organization of the human mitochondrial transcription initiation complex.
abstract: Initiation of transcription in human mitochondria involves two factors, TFAM and TFB2M, in addition to the mitochondrial RNA polymerase, POLRMT. We have investigated the organization of the human mitochondrial transcription initiation complex on the light-strand promoter (LSP) through solution X-ray scattering, electron microscopy (EM) and biochemical studies. Our EM results demonstrate a compact organization of the initiation complex, suggesting that protein-protein interactions might help mediate initiation. We demonstrate that, in the absence of DNA, only POLRMT and TFAM form a stable interaction, albeit one with low affinity. This is consistent with the expected transient nature of the interactions necessary for initiation and implies that the promoter DNA acts as a scaffold that enables formation of the full initiation complex. Docking of known crystal structures into our EM maps results in a model for transcriptional initiation that strongly correlates with new and existing biochemical observations. Our results reveal the organization of TFAM, POLRMT and TFB2M around the LSP and represent the first structural characterization of the entire mitochondrial transcriptional initiation complex.
authors.affiliation: Department of Pharmacological Sciences, Stony Brook University, Stony Brook, NY 11794, Cryo-Electron Microscopy Facility, New York Structural Biology Center, New York, NY 10027 and Department of Biomedical Engineering, Boston University, Boston, MA 02215, USA.
authors.forename: Elena
authors.initials: E
authors.lastname: Yakubovskaya
authors.forename: Kip E
authors.initials: KE
authors.lastname: Guja
authors.forename: Edward T
authors.initials: ET
authors.lastname: Eng
authors.forename: Woo Suk
authors.initials: WS
authors.lastname: Choi
authors.forename: Edison
authors.initials: E
authors.lastname: Mejia
authors.forename: Dmitri
authors.initials: D
authors.lastname: Beglov
authors.forename: Mark
authors.initials: M
authors.lastname: Lukin
authors.forename: Dima
authors.initials: D
authors.lastname: Kozakov
authors.forename: Miguel
authors.initials: M
authors.lastname: Garcia-Diaz
mesh_terms: D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D008780:Methyltransferases / Q000737:chemistry*; D008928:Mitochondria / Q000235:genetics*; D024101:Mitochondrial Proteins / Q000737:chemistry* / Q000378:metabolism; D008958:Models, Molecular; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000737:chemistry* / Q000378:metabolism; D061785:Transcription Initiation, Genetic
chemical_list: D004268:DNA-Binding Proteins; D024101:Mitochondrial Proteins; C499631:TFAM protein, human; C499632:TFB1M protein, human; D014157:Transcription Factors; D008780:Methyltransferases; C462443:TFB2M protein, human; D012321:DNA-Directed RNA Polymerases; C519567:POLRMT protein, human