title: Transcriptional activation by mitochondrial transcription factor A involves preferential distortion of promoter DNA.
abstract: Mitochondrial transcription factor A (mtTFA/TFAM) is a nucleus-encoded, high-mobility-group-box (HMG-box) protein that regulates transcription of the mitochondrial genome by specifically recognizing light-strand and heavy-strand promoters (LSP, HSP1). TFAM also binds mitochondrial DNA in a non-sequence specific (NSS) fashion and facilitates its packaging into nucleoid structures. However, the requirement and contribution of DNA-bending for these two different binding modes has not been addressed in detail, which prompted this comparison of binding and bending properties of TFAM on promoter and non-promoter DNA. Promoter DNA increased the stability of TFAM to a greater degree than non-promoter DNA. However, the thermodynamic properties of DNA binding for TFAM with promoter and non-specific (NS) DNA were similar to each other and to other NSS HMG-box proteins. Fluorescence resonance energy transfer assays showed that TFAM bends promoter DNA to a greater degree than NS DNA. In contrast, TFAM lacking the C-terminal tail distorted both promoter and non-promoter DNA to a significantly reduced degree, corresponding with markedly decreased transcriptional activation capacity at LSP and HSP1 in vitro. Thus, the enhanced bending of promoter DNA imparted by the C-terminal tail is a critical component of the ability of TFAM to activate promoter-specific initiation by the core mitochondrial transcription machinery.
authors.affiliation: Department of Pharmacology, University of Colorado Denver, School of Medicine, 12801 E. 17th Ave, Aurora, CO 80045-0511, USA.
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Malarkey
authors.forename: Megan
authors.initials: M
authors.lastname: Bestwick
authors.forename: Jane E
authors.initials: JE
authors.lastname: Kuhlwilm
authors.forename: Gerald S
authors.initials: GS
authors.lastname: Shadel
authors.forename: Mair E A
authors.initials: ME
authors.lastname: Churchill
mesh_terms: D001483:Base Sequence; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D019277:Entropy; D006801:Humans; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D009690:Nucleic Acid Conformation; D011401:Promoter Regions, Genetic; D055550:Protein Stability; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation
chemical_list: D004272:DNA, Mitochondrial; D004268:DNA-Binding Proteins; D024101:Mitochondrial Proteins; C499631:TFAM protein, human; D014157:Transcription Factors