![](img026.GIF) |
The
next thing he had to do is show that this receptor can bind to cognate response elements
in the promoter for CYP3A, and he did that by doing a gel study, an electrophoretic
mobility shift assay, where you ask whether a particular protein can stick to a small
piece of DNA. The small piece of DNA migrates very quickly in an electrophoretic field, an
electrical field through a gel, but if a protein sticks to it, that larger complex
migrates more slowly and is retarded. He was able to
show that the PXR receptor can stick to this sequence in the promoter for CYP3A, but it
does so, and retards it, only in concert with another member of the family. So the
regulation of this is through a heterodymanic nuclear receptor process. |