Transcription factor

A transcription factor is a protein that binds to specific DNA sequences to activate or repress the transcription of target genes. It is the basic switch in gene regulatory networks: transcription factors read regulatory logic and convert it into patterns of gene expression. The combinatorial control of transcription — multiple factors binding to the same regulatory region to produce context-specific outcomes — is how a finite genome generates the vast diversity of cell types and developmental states. Without transcription factors, the genome is inert; with them, it becomes a dynamical system capable of self-organization.