Promoter selection in human mitochondria involves binding of a transcription factor to orientation-independent upstream regulatory elements

Cell. 1987 Jul 17;50(2):247-58. doi: 10.1016/0092-8674(87)90220-0.

Abstract

Selective transcription of human mitochondrial DNA requires a transcription factor (mtTF) in addition to an essentially nonselective RNA polymerase. Partially purified mtTF is able to sequester promoter-containing DNA in preinitiation complexes in the absence of mitochondrial RNA polymerase, suggesting a DNA-binding mechanism for factor activity. Functional domains, required for positive transcriptional regulation by mtTF, are identified within both major promoters of human mtDNA through transcription of mutant promoter templates in a reconstituted in vitro system. These domains are essentially coextensive with DNA sequences protected from nuclease digestion by mtTF-binding. Comparison of the sequences of the two mtTF-responsive elements reveals significant homology only when one sequence is inverted; the binding sites are in opposite orientations with respect to the predominant direction of transcription. Thus mtTF may function bidirectionally, requiring additional protein-DNA interactions to dictate transcriptional polarity. The mtTF-responsive elements are arrayed as direct repeats, separated by approximately 80 bp within the displacement-loop region of human mitochondrial DNA; this arrangement may reflect duplication of an ancestral bidirectional promoter, giving rise to separate, unidirectional promoters for each strand.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • DNA, Mitochondrial / genetics*
  • DNA-Directed RNA Polymerases / metabolism
  • Genes, Regulator*
  • Humans
  • KB Cells
  • Mitochondria / metabolism
  • Promoter Regions, Genetic*
  • Templates, Genetic
  • Transcription Factors / metabolism*
  • Transcription, Genetic*

Substances

  • DNA, Mitochondrial
  • Transcription Factors
  • DNA-Directed RNA Polymerases