Fluorescence Imaging Group

The MMTV array can be recognized as a bright object in the nucleoplasm following hormone stimulation. That this is the site of the active gene is shown by colocalization with the transcript from the reporter. See Experimental System. To study dynamics of transcription factor binding we have used Fluorescence Recovery After Photobleaching (FRAP).

In FRAP (see schematic above), a laser is used to bleach GFP-GR fluorescence at the MMTV array. The rate of fluorescence recover at this site reflects the rate of GFP-GR exchange at the site.

The significance of these observations is that they imply very dynamic behavior of the transcription apparatus. How then does transcription occur during such rapid exchanges?

As a first step, we want to understand why the glucocorticoid receptor exchanges so rapidly on DNA. To address this, we are examining various mutant GFP-GR's to determine which parts of the molecule are involved in this rapid exchange.