A transcription factor (blue) binds to DNA (red) and alters which genes are turned on, or expressed.
Image courtesy of David S. Goodsell, RCSB Protein Data Bank
Transcription factors are proteins that control which genes are turned on or off in the genome. They do so by binding to DNA and other proteins. Once bound to DNA, these proteins can promote or block the enzyme that controls the reading, or “transcription,” of genes, making genes more or less active.
Transcription factors are essential for the regulation of genes. For example, different genes are turned on in liver cells than in skin cells. Different genes are turned on in cancer cells than in healthy cells. Through the action of transcription factors, the various cells of the body, which all have the same genome, can function differently.
These proteins are so important to life that they are found in all living organisms. Roughly 8% of genes in the human genome encode transcription factors. They play important roles in development, the sending of signals within the cell, and the events in a cell that lead to division and duplication, known as the cell cycle. Several human diseases are linked to mutations in transcription factors, such as diabetes, autoimmune diseases, and cancer.