Once the extracellular signal has been tranferred through a series of proteins and into the nucleus, transcripton factors within the nucleus are activated and prepare the regulated gene for transcription. Clicking on each of the
thumbnail images will bring up a larger, labeled version of the
see the Flash movie for the following sequence of images,
The signal is again transferred by phosphorylation, this time to a transcription factor within the nucleus.
The transcription factor then binds to a section of DNA upstream of the transcription start site, called an enhancer region.
The transcription factor then moves to interact with the rest of the transcription initiation complex at the transcription start site.
Once the transcription complex is complete, transcription begins. The interaction of these factors allows the cell to control transcription levels for specific genes, ensuring that certain proteins will be provided at the right concentrations at the required times.