Sequence-specific Positioning of Nucleosomes Over the Steroid-Inducible MMTV Promoter

EMBO J. 1987 Aug;6(8):2321-8.

Abstract

We have investigated chromatin organization over the MMTV LTR, a promoter regulated by steroid hormones. The studies were performed on cell lines containing BPV-based episomal constructs. Nucleosome positioning was determined by localization of sites sensitive to the enzyme micrococcal nuclease, or to the chemical MPE-Fe(II). Experiments with both reagents indicate that nucleosomes are specifically positioned in MMTV LTR chromatin. In the absence of hormone a regular cutting pattern is obtained, with cleavage sites at +136, -60, -250, -444, -651, -826 and -1019 relative to the Cap site. In the presence of hormone the cutting pattern is unchanged, except for a region between -60 and -250 that becomes hypersensitive to MPE-Fe(II). This region contains the DNA sequences to which steroid receptor complexes bind during transcriptional activation. Our results indicate that this region is associated in chromatin from uninduced cells with a macromolecular complex (probably a nucleosome core), and this complex is displaced (or modified) upon binding of activated receptor.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Cell Line
  • Chromatin / physiology
  • DNA Restriction Enzymes
  • Dexamethasone / pharmacology*
  • Gene Amplification
  • Genes, Regulator* / drug effects
  • Genes, Viral* / drug effects
  • Mammary Tumor Virus, Mouse / drug effects
  • Mammary Tumor Virus, Mouse / genetics*
  • Nucleosomes / physiology*
  • Promoter Regions, Genetic* / drug effects

Substances

  • Chromatin
  • Nucleosomes
  • Dexamethasone
  • DNA Restriction Enzymes