Sequence-specific positioning of nucleosomes over the steroid-inducible MMTV promoter.

AUTOR(ES)

Richard-Foy, H

RESUMO

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.

Documentos Relacionados

• A steroid-inducible promoter for the controlled overexpression of cloned genes in eukaryotic cells.
• A steroid-inducible gene expression system for plant cells.
• Evolution of Steroid-Inducible RP2 mRNA Expression in the Mouse Kidney
• Sequence-specific initiator elements focus initiation of transcription to distinct sites in the yeast TRP4 promoter.
• Use of the mouse mammary tumor virus long terminal repeat to promote steroid-inducible expression of v-mos.