Inverted factor access and slow reversion characterize SWI/SNF-altered nucleosome dimers

J Biol Chem. 2007 Jan 12;282(2):1018-28. doi: 10.1074/jbc.M609473200. Epub 2006 Nov 22.

Abstract

Human SWI/SNF (hSWI/SNF) is an ATP-dependent chromatin remodeling complex with important functions in activation and repression of cellular genes. Previously, we showed that hSWI/SNF creates structurally altered dimers from mononucleosome cores. More recently we found that hSWI/SNF also generates abundant structurally altered dinucleosomes, called altosomes, on polynucleosomal templates. Here, we find that dimers revert to normal nucleosomes at a similar rate as altosomes and can also be cleaved to yield nucleosomal particles with mobilities similar to mononucleosomes. Using these and other shared properties we propose a single model for both types of hSWI/SNF product. In addition, we further characterize the accessibility of altered dimers to transcription factors, and find that the DNA in dimers is most accessible in the middle and least accessible at the ends, directly opposite the profile of normal mononucleosomes. We also find that transcription factor binding can influence the ratio of normal nucleosomes and dimers as hSWI/SNF products. Implications for the interplay between hSWI/SNF products and transcription factors are discussed.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Chromatin / chemistry
  • Chromatin / metabolism
  • Chromosomal Proteins, Non-Histone / genetics
  • Chromosomal Proteins, Non-Histone / metabolism*
  • DNA / chemistry
  • DNA / metabolism
  • DNA-Binding Proteins
  • Dimerization
  • HeLa Cells
  • Humans
  • Nucleosomes / chemistry*
  • Nucleosomes / genetics
  • Nucleosomes / metabolism*
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Transcription, Genetic / physiology

Substances

  • Chromatin
  • Chromosomal Proteins, Non-Histone
  • DNA-Binding Proteins
  • GAL4 protein, S cerevisiae
  • Nucleosomes
  • SWI-SNF-B chromatin-remodeling complex
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors
  • DNA