What kind of TFs exist/ must all TFs be activated?
General TFs are necessary for the general transcription process. They don’t require an additional activation on the protein level as they are constitutively active. Some of the regulatory TFs only need an incoming signal for the cell to be produced. After such TFs are produced they are translocated immediately to the nucleus with out requirement of any additional activation. Signal dependent TFs are (either developmentally restricted in their expression or) present in most or all cells, but all are inactive (or minimally active) until cells containing such proteins are exposed to the appropriate intra- or extracellular signal (Brivanlou and Darnell, 2002, Science (295), pp813-818).
