Quantitation of glucocorticoid receptor DNA-binding dynamics by single-molecule microscopy and FRAP

PLoS One. 2014 Mar 14;9(3):e90532. doi: 10.1371/journal.pone.0090532. eCollection 2014.

Abstract

Recent advances in live cell imaging have provided a wealth of data on the dynamics of transcription factors. However, a consistent quantitative description of these dynamics, explaining how transcription factors find their target sequences in the vast amount of DNA inside the nucleus, is still lacking. In the present study, we have combined two quantitative imaging methods, single-molecule microscopy and fluorescence recovery after photobleaching, to determine the mobility pattern of the glucocorticoid receptor (GR) and the mineralocorticoid receptor (MR), two ligand-activated transcription factors. For dexamethasone-activated GR, both techniques showed that approximately half of the population is freely diffusing, while the remaining population is bound to DNA. Of this DNA-bound population about half the GRs appeared to be bound for short periods of time (∼ 0.7 s) and the other half for longer time periods (∼ 2.3 s). A similar pattern of mobility was seen for the MR activated by aldosterone. Inactive receptors (mutant or antagonist-bound receptors) show a decreased DNA binding frequency and duration, but also a higher mobility for the diffusing population. Likely, very brief (≤ 1 ms) interactions with DNA induced by the agonists underlie this difference in diffusion behavior. Surprisingly, different agonists also induce different mobilities of both receptors, presumably due to differences in ligand-induced conformational changes and receptor complex formation. In summary, our data provide a consistent quantitative model of the dynamics of GR and MR, indicating three types of interactions with DNA, which fit into a model in which frequent low-affinity DNA binding facilitates the search for high-affinity target sequences.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • COS Cells
  • Cell Line, Tumor
  • Chlorocebus aethiops
  • DNA / metabolism*
  • Fluorescence Recovery After Photobleaching / methods*
  • Humans
  • Microscopy / methods*
  • Models, Theoretical
  • Protein Binding
  • Receptors, Glucocorticoid / metabolism*
  • Receptors, Mineralocorticoid / metabolism

Substances

  • Receptors, Glucocorticoid
  • Receptors, Mineralocorticoid
  • DNA

Grant support

FLG and ERdK are supported by the Royal Netherlands Academy for Arts and Sciences, MvR by the Netherlands Organization for Scientific Research (NWO-STW), VIPK by the Foundation for Fundamental Research on Matter (FOM), and MJMS by the SmartMix Program of The Netherlands Ministry of Economic Affairs and the Ministry of Education, Culture and Science. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.