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Nucleic Acids Res ; 40(2): 614-24, 2012 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-21948790

RESUMO

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.


Assuntos
DNA Mitocondrial/metabolismo , Proteínas de Ligação a DNA/metabolismo , Proteínas Mitocondriais/metabolismo , Regiões Promotoras Genéticas , Fatores de Transcrição/metabolismo , Ativação Transcricional , Sequência de Bases , DNA Mitocondrial/química , Proteínas de Ligação a DNA/genética , Entropia , Humanos , Proteínas Mitocondriais/genética , Dados de Sequência Molecular , Mutação , Conformação de Ácido Nucleico , Estabilidade Proteica , Fatores de Transcrição/genética
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