I have an inquiry regarding the regulation of genes via extracellular signaling.
To my knowledge, in autocrine, paracrine, and endocrine cellular communication, large protein ligands that cannot directly diffuse through the plasma membrane of the target cell(s) use surface receptors to perform their desired action on the target cell(s).
I have learned that some of these ligands activate signal transduction pathways such as the MAPK/ERK and JAK/STAT pathway and drive the expression of specific genes by utilizing transcription factors (of course, in eukaryots). A simple example of this would be the action of epinephrine (adrenaline) on hepatocytes (liver cells), where the amino acid-based hormone uses the transcription factor CREB to express the gene coding for Glycogen Phosphorylase to engage in glycogenolysis.
Here I have two questions:
How does the transcription factor chemically indicate which gene to express? (Is there a gene indexing system like a computer filesystem?)
How does the transcription factor locate and bind to the promoter of the gene it is trying to express?