Dynamic exchange at regulatory elements during chromatin remodeling underlies assisted loading mechanism

Cell. 2011 Aug 19;146(4):544-54. doi: 10.1016/j.cell.2011.07.006. Epub 2011 Aug 11.


The glucocorticoid receptor (GR), like other eukaryotic transcription factors, regulates gene expression by interacting with chromatinized DNA response elements. Photobleaching experiments in living cells indicate that receptors transiently interact with DNA on the time scale of seconds and predict that the response elements may be sparsely occupied on average. Here, we show that the binding of one receptor at the glucocorticoid response element (GRE) does not reduce the steady-state binding of another receptor variant to the same GRE. Mathematical simulations reproduce this noncompetitive state using short GR/GRE residency times and relatively long times between DNA binding events. At many genomic sites where GR binding causes increased chromatin accessibility, concurrent steady-state binding levels for the variant receptor are actually increased, a phenomenon termed assisted loading. Temporally sparse transcription factor-DNA interactions induce local chromatin reorganization, resulting in transient access for binding of secondary regulatory factors.

Publication types

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

MeSH terms

  • Adenosine Triphosphate / metabolism
  • Animals
  • Cell Line, Tumor
  • Chromatin Assembly and Disassembly*
  • Mammary Tumor Virus, Mouse
  • Mice
  • Models, Biological
  • Monte Carlo Method
  • Nucleosomes / metabolism
  • Receptors, Estrogen / metabolism
  • Receptors, Glucocorticoid / metabolism*
  • Regulatory Sequences, Nucleic Acid
  • Response Elements*
  • Transcription Factors / metabolism


  • Nucleosomes
  • Receptors, Estrogen
  • Receptors, Glucocorticoid
  • Transcription Factors
  • Adenosine Triphosphate