Biology – Gene control | e-Consult

Transcription factors are proteins that bind to specific DNA sequences, typically located in the promoter region of a gene. This binding event is the first step in regulating gene transcription. They act as activators or repressors, influencing the rate at which RNA polymerase transcribes the DNA into mRNA.

How Transcription Factors Control Transcription:

• Activators: These transcription factors bind to DNA sequences near the promoter and recruit other proteins, including RNA polymerase and co-activators. This assembly of the transcriptional machinery enhances the transcription rate. Activators often promote chromatin remodeling, making the DNA more accessible to RNA polymerase.
• Repressors: These transcription factors bind to DNA sequences, often in regions distal to the promoter, and block the binding of RNA polymerase or co-activators. They may also recruit co-repressors that modify chromatin structure to make the DNA less accessible. This reduces the transcription rate.

Interaction with Cellular Components:

• Transcription factors often interact with other proteins, such as chromatin remodeling complexes (e.g., SWI/SNF) and histone modifying enzymes (e.g., histone acetyltransferases and deacetylases). These interactions alter the structure of chromatin, influencing the accessibility of DNA to RNA polymerase.
• They can also interact with signaling pathways. For example, a signal from a hormone can activate a signaling cascade that ultimately leads to the activation of a transcription factor.

Examples of transcription factors include: p53 (a tumor suppressor that activates genes involved in DNA repair and apoptosis), Steroid hormone receptors (which regulate gene expression in response to steroid hormones), and NF-κB (involved in inflammation and immune responses).